Why does my rear kick out to the left?
01-27-2009, 12:42 PM
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Why does my rear kick out to the left? It's an '01 Z28, stock suspension, boxed stock LCA's and poly bushings.
When I heat the tires up at the track the rear slides out to where the car is angled and pointing at the tree. (when I'm in the left lane)
And when I launch hard and break traction on the street or track the left rear slides over still.
My SS never did this when it was stock.
Any ideas?
When I heat the tires up at the track the rear slides out to where the car is angled and pointing at the tree. (when I'm in the left lane)
And when I launch hard and break traction on the street or track the left rear slides over still.
My SS never did this when it was stock.
Any ideas?
01-27-2009, 01:32 PM
#3
Rear Problem Hello,
Is this happening with those wore out Nitto Drag radials I see that you are using! If that is the case tires could be contributing to this problem.
Thanks Again,
Brad
Is this happening with those wore out Nitto Drag radials I see that you are using! If that is the case tires could be contributing to this problem.
Thanks Again,
Brad
01-27-2009, 08:09 PM
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The bushings are good, the LCA bushings are new energy suspension.
The tires aren't even drag radials lol, but they do grip pretty good for now.
It's just making the track officials nervous when the rear slides around and the car ends up facing in their direction while doing my burnout.
And my first run at the our remodeled track here I was in the right lane and got a bit loose, I ended up in 3rd headed toward the wall before I let off.
Looks like I should get some tires.
Thanks guys.
The tires aren't even drag radials lol, but they do grip pretty good for now.
It's just making the track officials nervous when the rear slides around and the car ends up facing in their direction while doing my burnout.
And my first run at the our remodeled track here I was in the right lane and got a bit loose, I ended up in 3rd headed toward the wall before I let off.
Looks like I should get some tires.
Thanks guys.
01-27-2009, 09:26 PM
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Mine also does this. When in the right hand lane, it points me towards the wall in my burnout. Makes me abit nervous but I just make sure it doesnt hook up untill I get it straight. Makes for pro stock style burnouts. haha. I think my posi unit is going out because I think one tire is spinning faster then the other, causing the car to turn that way. I just put some heavier (75-140) gear oil in it so hopefully that will help out.
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01-27-2009, 10:19 PM
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It's probably is more than tires though you could swap sides and verify. When the driveshaft torque loads the rear axle the right rear tire is being lifted and the left is being planted. The left then drives the car pushing it out left around the rest of the chassis while the right just smokes without much grip. All live axle chassis will do this naturally because the drive shaft twists the axle housing this direction unless some form of counteraction or preload is used against it.
Mine has done it to excess like yours for two different reasons now. The first one took me about a year to figure out because I kept adding high performance suspension parts to fix it without finding the real problem. One of my front springs was sagging causing the chassis to teeter over the other corners. I couldn't load the LR tire at rest and then it would unload the RR at launch and just wag back and forth violently switching sides. I either got no traction from launch or came close to loosing control at gear changes. One day in a level lot I noticed the rear of the car had a lean to it and found the RF sitting over 3/4 lower than the LF. I obtained a fresher set of SLP springs (it's a Firehawk) and also checked all eight of them with a spring scale. The RF was bad and the RR was weaker than the LR. In the rear suspension the driveshaft torque against a high static load will twist the RR axle up, my rear springs were the opposite of what would balance this. You want the RR to be stiffer than the LR for a more balanced load on the rear tires at launch. I installed good front springs and picked the stiffest rear spring I had for the RH and put a middle range one in the LH. This made the car launch harder than ever and all of my suspension upgrades were able to work as expected. I also then added a larger rear anti-sway bar to absorb more of the drive shaft torque and keep the rear flatter under twisting force. This works well and went for about a year. The car would even hook in the rain and with Firestone Firehawks it hooked good on the street. About two months ago I was burning out and leaving hard in first, when the A4 caught second I heard and felt a big pop in the rear end. I backed off but wasn't able to see, find, or feel anything wrong. I looked under the car the next day but everything was in place and I couldn't find any free play in the suspension. But after that the car was kicking out to the left like yours. I don't do many, well any, stationary burn outs but every WOT gear change would generate a big loss of traction and the rear end swinging out to the left. This was very hard to live with since I had fought so hard to get the car to hook right for so long already. I was suspecting the differential also. Well last week I started working under the car on the lift. I was installing rubber rod ends, shorter end links on the anti-sway bar, and new bump stops. When I took the lower control arms down I found that both front rod ends had loose jam-nuts. Both rear jam-nuts were still tight preventing the arms from twisting but it allowed for excessive free play in the control arm angles. This was allowing for enough twist to unload the RR but the LR would stay loaded like you're experiencing. After fixing it all back up it's working right again.
You may not have anything loose but it could be that you need to swap your rear springs side to side if you have the stronger one on the left, it should be on the right. If you can find a spring scale (think circle track shop) check them or just switch them around and retest. Make sure your chassis sits evenly, as with mine front springs will screw it up. Those drag launch springs are set up like that with an adjustable air spring in the RR also and front springs that like to unload to transfer load off the front and onto the rear.
An SS is like a Firehawk, it comes new with some suspension upgrades. One of them is stiffer bushings in the panhard bar. This is the bar that holds the rear centered left to right in the chassis. Soft GM spec bushings will give quite a bit under a hard, drag racing style launch. This could allow your rear to shift towards the tire with the most grip. Even though you've boxed the control arms installing a heavy duty panhard bar is required for good extreme performance. You can use rod ends on this part without the noise penalty and they work better than even poly at resisting deflection.
If you have a small rear anti-sway bar then installing a larger one will better resist the drive shaft and hold the axle flatter on the ground thereby giving more equal traction and thrust. I used a 21 mm from a 3rd gen to maintain handling balance with the SLP front but larger ones are even more effective for drag racing.
Since your suspension is stock then you have a suspension set-up that when faced with the rear axles providing foward thrust, will fold up into the chassis. This is due to the angles of the control arms compared to the torque arm and the wheel base of the chassis. This is called squat because as the suspension pulls itself up gravity just lowers the body onto it and the tires just skim on the road surface at the combined edge of grip and lift until the chassis is at maximum achievable squat. Also the suspension will not be able to lift the front because the stock arm angles try to lift car from about the front wheels. There is usually not enough traction in a stock suspension on drag radials to lift that much of the chassis very high. Load transfer is minimal. Since your RR is already being excessively unloaded it only make the situation worse on the right side. The car leaves but not very hard and never gets a good bite. Soft bushings throughout the stock suspension make the tire loading a constant variable and wheel hop is common place. Stiffer bushing reduce these traction oscillations and therefore reduce wheel hop but don't increase the tire loading. This is done on purpose to prevent a hard launch and loss of control due to the soft suspension or broken cars in for warranty work.
There are a bunch of things you can do to change this and actually generate chassis lift or anti-squat but the two most popular are a shorter torque arm and lower control arm relocation brackets. The shorter torque arm or tunnel mount will bring the axle's forward twist (not drive shaft twist) lifting point further back into the chassis. This means the rear suspension is now lifting less of the car, the rear. Since the rear of the car is much lighter than the whole car with front end included the rear of the chassis is pushed up against gravity with axle thrust. This means the tires are pushed down onto the ground and grip is increased greatly at launch. This is good up until the point that the suspension tops out the shocks and anti-squat instantly goes away. If you set the chassis up for it you can move more weight towards the rear, like the battery, and set the front end up to lift more like loose shocks and therefore add more load onto the rear suspension as the car is launched to keep the rear axle and chassis loaded in back and down. Usually these cars are rolling out well before you can top the shocks, they are pretty light in the front end but tuning still helps go harder. Heavy older iron with a lot of rear anti-squat can top the shocks pushing a heavy front end forward.
The other popular and easy modification to the rear suspension to generate anti-squat is lower control arm relocation brackets. These drop the lower arm rear axle mounting points down so that the arms now angle the forward axle thrust (think push) into the chassis at more of an upward angle. So now forward thrust of the axle pushes the car forward and up. Therefore also using gravity to increase tire loading.
Both of these anti-squat mods will also counteract the lift generated on the RR tire due to drive shaft torque against the axle further helping your one wheel drive launching problems.
I doubt it's your limited slip because if it was you would be smoking the RR and going strait. The RR unloads with drive shaft torque and without some axle traction equalizer will just raise and spin. From your description it sounds like your LR is pushing the car around the unloaded RR.
Find out why your only loading your LR and fix that. look hard and check every fastener and bushing. Stiffen up the suspension and install some anti-squat. Move weight back and loosen up the front end. You'll get a great launching car. It's there somewhere you just have to find it, hopefully this long read will save you a lot of time and head scratching, I wish I had it when I was trying to fix mine.
Vernon
Mine has done it to excess like yours for two different reasons now. The first one took me about a year to figure out because I kept adding high performance suspension parts to fix it without finding the real problem. One of my front springs was sagging causing the chassis to teeter over the other corners. I couldn't load the LR tire at rest and then it would unload the RR at launch and just wag back and forth violently switching sides. I either got no traction from launch or came close to loosing control at gear changes. One day in a level lot I noticed the rear of the car had a lean to it and found the RF sitting over 3/4 lower than the LF. I obtained a fresher set of SLP springs (it's a Firehawk) and also checked all eight of them with a spring scale. The RF was bad and the RR was weaker than the LR. In the rear suspension the driveshaft torque against a high static load will twist the RR axle up, my rear springs were the opposite of what would balance this. You want the RR to be stiffer than the LR for a more balanced load on the rear tires at launch. I installed good front springs and picked the stiffest rear spring I had for the RH and put a middle range one in the LH. This made the car launch harder than ever and all of my suspension upgrades were able to work as expected. I also then added a larger rear anti-sway bar to absorb more of the drive shaft torque and keep the rear flatter under twisting force. This works well and went for about a year. The car would even hook in the rain and with Firestone Firehawks it hooked good on the street. About two months ago I was burning out and leaving hard in first, when the A4 caught second I heard and felt a big pop in the rear end. I backed off but wasn't able to see, find, or feel anything wrong. I looked under the car the next day but everything was in place and I couldn't find any free play in the suspension. But after that the car was kicking out to the left like yours. I don't do many, well any, stationary burn outs but every WOT gear change would generate a big loss of traction and the rear end swinging out to the left. This was very hard to live with since I had fought so hard to get the car to hook right for so long already. I was suspecting the differential also. Well last week I started working under the car on the lift. I was installing rubber rod ends, shorter end links on the anti-sway bar, and new bump stops. When I took the lower control arms down I found that both front rod ends had loose jam-nuts. Both rear jam-nuts were still tight preventing the arms from twisting but it allowed for excessive free play in the control arm angles. This was allowing for enough twist to unload the RR but the LR would stay loaded like you're experiencing. After fixing it all back up it's working right again.
You may not have anything loose but it could be that you need to swap your rear springs side to side if you have the stronger one on the left, it should be on the right. If you can find a spring scale (think circle track shop) check them or just switch them around and retest. Make sure your chassis sits evenly, as with mine front springs will screw it up. Those drag launch springs are set up like that with an adjustable air spring in the RR also and front springs that like to unload to transfer load off the front and onto the rear.
An SS is like a Firehawk, it comes new with some suspension upgrades. One of them is stiffer bushings in the panhard bar. This is the bar that holds the rear centered left to right in the chassis. Soft GM spec bushings will give quite a bit under a hard, drag racing style launch. This could allow your rear to shift towards the tire with the most grip. Even though you've boxed the control arms installing a heavy duty panhard bar is required for good extreme performance. You can use rod ends on this part without the noise penalty and they work better than even poly at resisting deflection.
If you have a small rear anti-sway bar then installing a larger one will better resist the drive shaft and hold the axle flatter on the ground thereby giving more equal traction and thrust. I used a 21 mm from a 3rd gen to maintain handling balance with the SLP front but larger ones are even more effective for drag racing.
Since your suspension is stock then you have a suspension set-up that when faced with the rear axles providing foward thrust, will fold up into the chassis. This is due to the angles of the control arms compared to the torque arm and the wheel base of the chassis. This is called squat because as the suspension pulls itself up gravity just lowers the body onto it and the tires just skim on the road surface at the combined edge of grip and lift until the chassis is at maximum achievable squat. Also the suspension will not be able to lift the front because the stock arm angles try to lift car from about the front wheels. There is usually not enough traction in a stock suspension on drag radials to lift that much of the chassis very high. Load transfer is minimal. Since your RR is already being excessively unloaded it only make the situation worse on the right side. The car leaves but not very hard and never gets a good bite. Soft bushings throughout the stock suspension make the tire loading a constant variable and wheel hop is common place. Stiffer bushing reduce these traction oscillations and therefore reduce wheel hop but don't increase the tire loading. This is done on purpose to prevent a hard launch and loss of control due to the soft suspension or broken cars in for warranty work.
There are a bunch of things you can do to change this and actually generate chassis lift or anti-squat but the two most popular are a shorter torque arm and lower control arm relocation brackets. The shorter torque arm or tunnel mount will bring the axle's forward twist (not drive shaft twist) lifting point further back into the chassis. This means the rear suspension is now lifting less of the car, the rear. Since the rear of the car is much lighter than the whole car with front end included the rear of the chassis is pushed up against gravity with axle thrust. This means the tires are pushed down onto the ground and grip is increased greatly at launch. This is good up until the point that the suspension tops out the shocks and anti-squat instantly goes away. If you set the chassis up for it you can move more weight towards the rear, like the battery, and set the front end up to lift more like loose shocks and therefore add more load onto the rear suspension as the car is launched to keep the rear axle and chassis loaded in back and down. Usually these cars are rolling out well before you can top the shocks, they are pretty light in the front end but tuning still helps go harder. Heavy older iron with a lot of rear anti-squat can top the shocks pushing a heavy front end forward.
The other popular and easy modification to the rear suspension to generate anti-squat is lower control arm relocation brackets. These drop the lower arm rear axle mounting points down so that the arms now angle the forward axle thrust (think push) into the chassis at more of an upward angle. So now forward thrust of the axle pushes the car forward and up. Therefore also using gravity to increase tire loading.
Both of these anti-squat mods will also counteract the lift generated on the RR tire due to drive shaft torque against the axle further helping your one wheel drive launching problems.
I doubt it's your limited slip because if it was you would be smoking the RR and going strait. The RR unloads with drive shaft torque and without some axle traction equalizer will just raise and spin. From your description it sounds like your LR is pushing the car around the unloaded RR.
Find out why your only loading your LR and fix that. look hard and check every fastener and bushing. Stiffen up the suspension and install some anti-squat. Move weight back and loosen up the front end. You'll get a great launching car. It's there somewhere you just have to find it, hopefully this long read will save you a lot of time and head scratching, I wish I had it when I was trying to fix mine.
Vernon
Last edited by Manic Mechanic; 01-27-2009 at 10:26 PM.
01-27-2009, 10:20 PM
#9
Just keep your front tires pointed straight down the track and no one should get too nervous.
As far as what causes it, I have no idea, mines been doing that for as long as I can remember, it could be track conditions (the groove), could be rear end, could be a lot of things really, but I'm personally not gonna stress till somthing breaks. But hey that's me.
01-27-2009, 10:26 PM
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IF, and I state IF, tires and posy are good you should get a good complete alignment
front and rear, the rear thrust line shoukd be less than .013 eather + or -,if thrust line is - rear will walk to left, if + rear will walk to right ( when you nail it ) best would need to be very little +, if beyound this I suggest a set of adjustable REAR LOWER CONTROL ARMS
good luck, Johnny
front and rear, the rear thrust line shoukd be less than .013 eather + or -,if thrust line is - rear will walk to left, if + rear will walk to right ( when you nail it ) best would need to be very little +, if beyound this I suggest a set of adjustable REAR LOWER CONTROL ARMS
good luck, Johnny
01-27-2009, 10:35 PM
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It's probably is more than tires though you could swap sides and verify. When the driveshaft torque loads the rear axle the right rear tire is being lifted and the left is being planted. The left then drives the car pushing it out left around the rest of the chassis while the right just smokes without much grip. All live axle chassis will do this naturally because the drive shaft twists the axle housing this direction unless some form of counteraction or preload is used against it.
Mine has done it to excess like yours for two different reasons now. The first one took me about a year to figure out because I kept adding high performance suspension parts to fix it without finding the real problem. One of my front springs was sagging causing the chassis to teeter over the other corners. I couldn't load the LR tire at rest and then it would unload the RR at launch and just wag back and forth violently switching sides. I either got no traction from launch or came close to loosing control at gear changes. One day in a level lot I noticed the rear of the car had a lean to it and found the RF sitting over 3/4 lower than the LF. I obtained a fresher set of SLP springs (it's a Firehawk) and also checked all eight of them with a spring scale. The RF was bad and the RR was weaker than the LR. In the rear suspension the driveshaft torque against a high static load will twist the RR axle up, my rear springs were the opposite of what would balance this. You want the RR to be stiffer than the LR for a more balanced load on the rear tires at launch. I installed good front springs and picked the stiffest rear spring I had for the RH and put a middle range one in the LH. This made the car launch harder than ever and all of my suspension upgrades were able to work as expected. I also then added a larger rear anti-sway bar to absorb more of the drive shaft torque and keep the rear flatter under twisting force. This works well and went for about a year. The car would even hook in the rain and with Firestone Firehawks it hooked good on the street. About two months ago I was burning out and leaving hard in first, when the A4 caught second I heard and felt a big pop in the rear end. I backed off but wasn't able to see, find, or feel anything wrong. I looked under the car the next day but everything was in place and I couldn't find any free play in the suspension. But after that the car was kicking out to the left like yours. I don't do many, well any, stationary burn outs but every WOT gear change would generate a big loss of traction and the rear end swinging out to the left. This was very hard to live with since I had fought so hard to get the car to hook right for so long already. I was suspecting the differential also. Well last week I started working under the car on the lift. I was installing rubber rod ends, shorter end links on the anti-sway bar, and new bump stops. When I took the lower control arms down I found that both front rod ends had loose jam-nuts. Both rear jam-nuts were still tight preventing the arms from twisting but it allowed for excessive free play in the control arm angles. This was allowing for enough twist to unload the RR but the LR would stay loaded like you're experiencing. After fixing it all back up it's working right again.
You may not have anything loose but it could be that you need to swap your rear springs side to side if you have the stronger one on the left, it should be on the right. If you can find a spring scale (think circle track shop) check them or just switch them around and retest. Make sure your chassis sits evenly, as with mine front springs will screw it up. Those drag launch springs are set up like that with an adjustable air spring in the RR also and front springs that like to unload to transfer load off the front and onto the rear.
An SS is like a Firehawk, it comes new with some suspension upgrades. One of them is stiffer bushings in the panhard bar. This is the bar that holds the rear centered left to right in the chassis. Soft GM spec bushings will give quite a bit under a hard, drag racing style launch. This could allow your rear to shift towards the tire with the most grip. Even though you've boxed the control arms installing a heavy duty panhard bar is required for good extreme performance. You can use rod ends on this part without the noise penalty and they work better than even poly at resisting deflection.
If you have a small rear anti-sway bar then installing a larger one will better resist the drive shaft and hold the axle flatter on the ground thereby giving more equal traction and thrust. I used a 21 mm from a 3rd gen to maintain handling balance with the SLP front but larger ones are even more effective for drag racing.
Since your suspension is stock then you have a suspension set-up that when faced with the rear axles providing foward thrust, will fold up into the chassis. This is due to the angles of the control arms compared to the torque arm and the wheel base of the chassis. This is called squat because as the suspension pulls itself up gravity just lowers the body onto it and the tires just skim on the road surface at the combined edge of grip and lift until the chassis is at maximum achievable squat. Also the suspension will not be able to lift the front because the stock arm angles try to lift car from about the front wheels. There is usually not enough traction in a stock suspension on drag radials to lift that much of the chassis very high. Load transfer is minimal. Since your RR is already being excessively unloaded it only make the situation worse on the right side. The car leaves but not very hard and never gets a good bite. Soft bushings throughout the stock suspension make the tire loading a constant variable and wheel hop is common place. Stiffer bushing reduce these traction oscillations and therefore reduce wheel hop but don't increase the tire loading. This is done on purpose to prevent a hard launch and loss of control due to the soft suspension or broken cars in for warranty work.
There are a bunch of things you can do to change this and actually generate chassis lift or anti-squat but the two most popular are a shorter torque arm and lower control arm relocation brackets. The shorter torque arm or tunnel mount will bring the axle's forward twist (not drive shaft twist) lifting point further back into the chassis. This means the rear suspension is now lifting less of the car, the rear. Since the rear of the car is much lighter than the whole car with front end included the rear of the chassis is pushed up against gravity with axle thrust. This means the tires are pushed down onto the ground and grip is increased greatly at launch. This is good up until the point that the suspension tops out the shocks and anti-squat instantly goes away. If you set the chassis up for it you can move more weight towards the rear, like the battery, and set the front end up to lift more like loose shocks and therefore add more load onto the rear suspension as the car is launched to keep the rear axle and chassis loaded in back and down. Usually these cars are rolling out well before you can top the shocks, they are pretty light in the front end but tuning still helps go harder. Heavy older iron with a lot of rear anti-squat can top the shocks pushing a heavy front end forward.
The other popular and easy modification to the rear suspension to generate anti-squat is lower control arm relocation brackets. These drop the lower arm rear axle mounting points down so that the arms now angle the forward axle thrust (think push) into the chassis at more of an upward angle. So now forward thrust of the axle pushes the car forward and up. Therefore also using gravity to increase tire loading.
Both of these anti-squat mods will also counteract the lift generated on the RR tire due to drive shaft torque against the axle further helping your one wheel drive launching problems.
I doubt it's your limited slip because if it was you would be smoking the RR and going strait. The RR unloads with drive shaft torque and without some axle traction equalizer will just raise and spin. From your description it sounds like your LR is pushing the car around the unloaded RR.
Find out why your only loading your LR and fix that. look hard and check every fastener and bushing. Stiffen up the suspension and install some anti-squat. Move weight back and loosen up the front end. You'll get a great launching car. It's there somewhere you just have to find it, hopefully this long read will save you a lot of time and head scratching, I wish I had it when I was trying to fix mine.
Vernon
Mine has done it to excess like yours for two different reasons now. The first one took me about a year to figure out because I kept adding high performance suspension parts to fix it without finding the real problem. One of my front springs was sagging causing the chassis to teeter over the other corners. I couldn't load the LR tire at rest and then it would unload the RR at launch and just wag back and forth violently switching sides. I either got no traction from launch or came close to loosing control at gear changes. One day in a level lot I noticed the rear of the car had a lean to it and found the RF sitting over 3/4 lower than the LF. I obtained a fresher set of SLP springs (it's a Firehawk) and also checked all eight of them with a spring scale. The RF was bad and the RR was weaker than the LR. In the rear suspension the driveshaft torque against a high static load will twist the RR axle up, my rear springs were the opposite of what would balance this. You want the RR to be stiffer than the LR for a more balanced load on the rear tires at launch. I installed good front springs and picked the stiffest rear spring I had for the RH and put a middle range one in the LH. This made the car launch harder than ever and all of my suspension upgrades were able to work as expected. I also then added a larger rear anti-sway bar to absorb more of the drive shaft torque and keep the rear flatter under twisting force. This works well and went for about a year. The car would even hook in the rain and with Firestone Firehawks it hooked good on the street. About two months ago I was burning out and leaving hard in first, when the A4 caught second I heard and felt a big pop in the rear end. I backed off but wasn't able to see, find, or feel anything wrong. I looked under the car the next day but everything was in place and I couldn't find any free play in the suspension. But after that the car was kicking out to the left like yours. I don't do many, well any, stationary burn outs but every WOT gear change would generate a big loss of traction and the rear end swinging out to the left. This was very hard to live with since I had fought so hard to get the car to hook right for so long already. I was suspecting the differential also. Well last week I started working under the car on the lift. I was installing rubber rod ends, shorter end links on the anti-sway bar, and new bump stops. When I took the lower control arms down I found that both front rod ends had loose jam-nuts. Both rear jam-nuts were still tight preventing the arms from twisting but it allowed for excessive free play in the control arm angles. This was allowing for enough twist to unload the RR but the LR would stay loaded like you're experiencing. After fixing it all back up it's working right again.
You may not have anything loose but it could be that you need to swap your rear springs side to side if you have the stronger one on the left, it should be on the right. If you can find a spring scale (think circle track shop) check them or just switch them around and retest. Make sure your chassis sits evenly, as with mine front springs will screw it up. Those drag launch springs are set up like that with an adjustable air spring in the RR also and front springs that like to unload to transfer load off the front and onto the rear.
An SS is like a Firehawk, it comes new with some suspension upgrades. One of them is stiffer bushings in the panhard bar. This is the bar that holds the rear centered left to right in the chassis. Soft GM spec bushings will give quite a bit under a hard, drag racing style launch. This could allow your rear to shift towards the tire with the most grip. Even though you've boxed the control arms installing a heavy duty panhard bar is required for good extreme performance. You can use rod ends on this part without the noise penalty and they work better than even poly at resisting deflection.
If you have a small rear anti-sway bar then installing a larger one will better resist the drive shaft and hold the axle flatter on the ground thereby giving more equal traction and thrust. I used a 21 mm from a 3rd gen to maintain handling balance with the SLP front but larger ones are even more effective for drag racing.
Since your suspension is stock then you have a suspension set-up that when faced with the rear axles providing foward thrust, will fold up into the chassis. This is due to the angles of the control arms compared to the torque arm and the wheel base of the chassis. This is called squat because as the suspension pulls itself up gravity just lowers the body onto it and the tires just skim on the road surface at the combined edge of grip and lift until the chassis is at maximum achievable squat. Also the suspension will not be able to lift the front because the stock arm angles try to lift car from about the front wheels. There is usually not enough traction in a stock suspension on drag radials to lift that much of the chassis very high. Load transfer is minimal. Since your RR is already being excessively unloaded it only make the situation worse on the right side. The car leaves but not very hard and never gets a good bite. Soft bushings throughout the stock suspension make the tire loading a constant variable and wheel hop is common place. Stiffer bushing reduce these traction oscillations and therefore reduce wheel hop but don't increase the tire loading. This is done on purpose to prevent a hard launch and loss of control due to the soft suspension or broken cars in for warranty work.
There are a bunch of things you can do to change this and actually generate chassis lift or anti-squat but the two most popular are a shorter torque arm and lower control arm relocation brackets. The shorter torque arm or tunnel mount will bring the axle's forward twist (not drive shaft twist) lifting point further back into the chassis. This means the rear suspension is now lifting less of the car, the rear. Since the rear of the car is much lighter than the whole car with front end included the rear of the chassis is pushed up against gravity with axle thrust. This means the tires are pushed down onto the ground and grip is increased greatly at launch. This is good up until the point that the suspension tops out the shocks and anti-squat instantly goes away. If you set the chassis up for it you can move more weight towards the rear, like the battery, and set the front end up to lift more like loose shocks and therefore add more load onto the rear suspension as the car is launched to keep the rear axle and chassis loaded in back and down. Usually these cars are rolling out well before you can top the shocks, they are pretty light in the front end but tuning still helps go harder. Heavy older iron with a lot of rear anti-squat can top the shocks pushing a heavy front end forward.
The other popular and easy modification to the rear suspension to generate anti-squat is lower control arm relocation brackets. These drop the lower arm rear axle mounting points down so that the arms now angle the forward axle thrust (think push) into the chassis at more of an upward angle. So now forward thrust of the axle pushes the car forward and up. Therefore also using gravity to increase tire loading.
Both of these anti-squat mods will also counteract the lift generated on the RR tire due to drive shaft torque against the axle further helping your one wheel drive launching problems.
I doubt it's your limited slip because if it was you would be smoking the RR and going strait. The RR unloads with drive shaft torque and without some axle traction equalizer will just raise and spin. From your description it sounds like your LR is pushing the car around the unloaded RR.
Find out why your only loading your LR and fix that. look hard and check every fastener and bushing. Stiffen up the suspension and install some anti-squat. Move weight back and loosen up the front end. You'll get a great launching car. It's there somewhere you just have to find it, hopefully this long read will save you a lot of time and head scratching, I wish I had it when I was trying to fix mine.
Vernon
01-27-2009, 10:51 PM
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Check tire pressures - adjust in 2lb increments to see if it affects the burnout/launch. Start with equal pressures in both rear tires. If the rear still slides, then either take air out of the LR or add air to the RR. Fine tune with smaller pressure adjustments depending on how the car reacts.
01-27-2009, 11:17 PM
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I really appreciate your time in writing that, I understand it all. I think the car does need LCA relocation brackets because even with stock springs the LCA's point downward toward the front.
This car use to run 6.4 in the 1/8th from the previous owner. A few people in the Texas forum actually recognized the car when I put up pics and named the guy. But I think the whole rear suspension was put back to stock before I got it, it had mismatched bolts and all.
It also had lowering springs in the back only. So I got stock rear springs from you know where (my sig)
So tires, relocation brackets and springs to start is what I'll do.
The last car I used to race was a '75 nova with a big block and slapper bars.
I had that car 18 years and could smoke the tires three blocks in a staight line, and even on a wet road going 90 it would kick a little to the right with a wot hit. That was real old school, one air shock for preload, etc, it worked well.
But I'm stepping up to the newer stuff 100% now.
I've got the SS with all the UMI stuff on the back but I don't drive it much. The car in this post is going to see the track, maybe often.
Thanks to everyone for the replies, BTW the rear thrust line IIRC was .003
This car use to run 6.4 in the 1/8th from the previous owner. A few people in the Texas forum actually recognized the car when I put up pics and named the guy. But I think the whole rear suspension was put back to stock before I got it, it had mismatched bolts and all.
It also had lowering springs in the back only. So I got stock rear springs from you know where (my sig)
So tires, relocation brackets and springs to start is what I'll do.
The last car I used to race was a '75 nova with a big block and slapper bars.
I had that car 18 years and could smoke the tires three blocks in a staight line, and even on a wet road going 90 it would kick a little to the right with a wot hit. That was real old school, one air shock for preload, etc, it worked well.
But I'm stepping up to the newer stuff 100% now.
I've got the SS with all the UMI stuff on the back but I don't drive it much. The car in this post is going to see the track, maybe often.
Thanks to everyone for the replies, BTW the rear thrust line IIRC was .003
