Manic Mechanic

iTrader: (3)

I've been struggling to get good bite for a while. I've tried many pinion angles and it seems if I could get it hooking a little better the driveshaft vibrations were unbearable. It's a 120K Firehawk with the stock SLP Lvl-2 shocks and springs on Firehawk radials. It's got a torsen with the 3.4x gear set. I've installed a Spohn tunnel mount adjustable torque arm, lower control arm relocation brackets, and Pavlock lower arms and pan-hard brace. The brackets are set on the upper or first anti-sqaut setting. When power braking the rear of the car will rise up like it should to load the tires. I don't think it tops out the shocks on a launch, there's just not enough static grip to hit the suspension that hard. On a hard lauch and also when the trans (A4) shifts the car will just spin like crazy. If I step into it slowly the car will usually leave street thugs by at least half a car. Also when the tranny grabs a gear at high speeds the rear end steps out violently and I have to stay on top of it. What I want is to pull the front end up and blast off like every other sig pic hero on the board. So far I've been throwing time and money at it with no good results.

Well today I had the car parked out front of the shop and facing away, it seemed the rear of the car was leaning towards the pass. side so I took a tape and measured all the fender opening hieghts and the pass front corner of the car is down 3/4" compared to the drivers rear and it pulls the left rear up. Most of my wieght is teetering on the LF and RR tires. I turned the car 180* and rechecked to rule out parking lot level and it was almost the same measurements. I don't have a full and even wieght load on the rear tires at rest, so that's probably a lot of my problem. My LR is being pulled up and I launch peg-legged, great.

The only things I can think of are a sagging spring, a bent frame, control arm or spindle. I would think that something bent would be unpredictable in turning which the car isn't. It's been wrecked (fender bender) in that corner but not even hard enough to replace the core support. There's no problems with leaking weater striping (t-top car) or door alignments. It seems fine and I've spent a lot of time under the car and never noticed anything. I did notice the RR lower control arm was tight and the LR was loose but figured it was joint binding and had the rear on stands anyways but the fronts were on ramps so it was still effected.

Is it likely just the RF spring or what else should I look at? Anyplace where these chassis are known to develop problems and what should I look for?

I'm just glad Pavlock was out of subframe connectors the other day. It would have sucked to have welded up a bent or twisted car. Now I can still fix it if needed or have it flat before it's stiched up.

Thanks for any advice, if anyone else has been here what did you find and do? Did it help, I'm about sick of no traction.

Vernon

Manic Mechanic

iTrader: (3)

Damn, 46 view and nobody has any other ideas? Well I guess it's just a spring then. That's good news if that's all it is.

Vernon

DopeFedZ

iTrader: (34)

What kind of tires are on the car? I've been trying to get mine to hook on the street and it will not hook from a dig. The only supsension pieces I have are the Spohn torque arm and BMR lca's. I race mine on 275/50/15 M/T drag radials and I can't get them to hook on motor even after a good burnout. I think adjustable shocks are needed to get it to hook up.

At the track traction isn't a issue but the street is a whole different story.

Manic Mechanic

iTrader: (3)

I guess I type so fast that I write too much and people loose track of all the info, I'm the king of unanswered posts. LOL
The tires are currently Firstone Firehawks, 275/40-17. Not the choice for drags I know but much better than the tires I replaced which were Kumho Ecsta speed radials. When I replaced them traction doubled.
Vernon

1CAMWNDR

iTrader: (21)

Sounds like one spring to me.

Manic Mechanic

iTrader: (3)

Thanks.

I was finally able to get it on an alignment rack today and everything else appears fine. It probably is just the spring. I'm working on a deal for some Firehawk take outs now.

Vernon

z28bryan

iTrader: (7)

Most of the cars are uneven in the rear. It happens to many of us.

Manic Mechanic

iTrader: (3)

Here's an intersting note on the Firehawk take out springs I bought. I got them and they look fresh so I took them to the local circle track supply house (Smiley's Racing in SW Montgomery Co.) to check them out on a spring rate checking press. The spring sets are identical in height and condition but here's what they showed when compressed to the same hieght (the machines digital micrometer had a low battery so I just went to the end of the analog scale and took wieghts). This was approximately 6-7 inches of compression.

Fronts: 550 and 570
Rear: 340 and 375

I'm going to pull out all of my stockers and measure them then pick springs. I'm going to put the stiffer front on the LH and the stiffer rear on the RH. and use the closest matches. This should provide a good hooking and handling combo.

The point I wanted to make is that just installing springs without checking them could be a waste of time or make things worse.

Vernon

JWS6

nice read.

Manic Mechanic

iTrader: (3)

Thanks Josh, I hope it helps somebody else. It's been driving me nuts. I'll keep up with the thread and report the outcome of a spring swap.

For those who don't know or never thought about it when you hit a live axle hard at any time but especially at rest the driveshafts torque against the captive gear set tries to twist the rear axle in the same direction due to the resistance of pushing the car foward at such a fast rate. So what happens is that the right rear tire gets unloaded and the left rear recieves that twisting load. It might seem that my sagging RF spring would help load the RR, but it didn't, it seemed to make it start with more grip on the RR and just spin. If I did get bite it just switched sides back and forth and fish tailed.

If you want to hook better and straighter by counter acting driveshaft torque there's a few common methods. Rear anti-sway bars absorb one sided loads by applying it to the opposite side. That's why the drag bars are so stout. Also setting up the springs for preloading the RR with more wieght is another, like the Eibach Drag Launch kit. I'm going to shoot for that method but on a more streetable scale. In any case if I had installed the rear springs with a stiffer on on the left it would have not been nearly as effective as putting the stiffer on the right side. By installing the stiffer front spring on the left it should help with the situation and help the car stay level. Plus when I'm really hauling azz I'm usually alone. If this works the next thing I'm going to do is move the battery to the right rear of the car also. I've done this on other cars and found the mod amazing for traction in every direction.

It'll be a week or two before I swap springs.

Later,
Vernon

anchov13

So did it turn out to be just the springs? I am experiencing the same "droop" on my 98 Trans Am, only its about 1/2 inch. I don't want to invest in some Koni SA right now if I dont have too.

Enforcerws6

iTrader: (1)

Manic wrote "The brackets are set on the upper or first anti-sqaut setting."


Do you mean the relo brackets have the lower control arms towards the top?????? You want them in the lower hole for best traction. This isnt ideal for handling but should give the best results for traction. You want the lower control arms headed upward from rear to front as much as possible. I didnt my rear chassis parts and put in a tunnel mount tq arm along with relos. The car will damn near dead hook off the line every time. This is a mostly stock ws6 lt1 with a 9 inch and 3.73 gears. Before I did all this work the car would never ever hook in first gear or shifting into second. A third to second down shift at certain times would take the rear tires loose ( highest rpm that it would still go down into second).