UMI torque arm adjustments??
10-19-2009, 03:50 PM
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UMI torque arm adjustments?? a few months back, I bought a tunnel mounted UMI t/a PN:2202 and put it in the car.
I noticed the "shackle" that connects the torque arm itself to the crossmember has 3 sets of holes in it. 1 for its attachment point to the crossmember, and 2 possible spots for the torque arm to locate from.
I currently have the t/a in the lower mount hole.
aside from the umi torque arm, the only suspension mods to the car are a set of LCA's, no front sway bar, and comp. engineering 3-way shocks in the back.
I'm having some serious traction issues with it right now. a 320rwhp car, with a 3400 converter, 3.73's and 28" m/t drag radials shouldnt have a problem hooking anywhere.
with a 5sec. 2nd gear burnout, preload, or just flash out of the hole, and it's effortless burnouts through 2nd gear, probably 3rd if I felt the need to waste any more tread life.
any input guys?
I noticed the "shackle" that connects the torque arm itself to the crossmember has 3 sets of holes in it. 1 for its attachment point to the crossmember, and 2 possible spots for the torque arm to locate from.
I currently have the t/a in the lower mount hole.
aside from the umi torque arm, the only suspension mods to the car are a set of LCA's, no front sway bar, and comp. engineering 3-way shocks in the back.
I'm having some serious traction issues with it right now. a 320rwhp car, with a 3400 converter, 3.73's and 28" m/t drag radials shouldnt have a problem hooking anywhere.
with a 5sec. 2nd gear burnout, preload, or just flash out of the hole, and it's effortless burnouts through 2nd gear, probably 3rd if I felt the need to waste any more tread life.
any input guys?
10-19-2009, 04:03 PM
#2
Staging Lane
I am having a similar problem. i don't think it matters which holes you use as long as you set the pinion angle correctly. I have mine set at a -1 and someone suggested to me to try even lower like -4 for best results while launching. What pinion angle do you have it set at?
10-19-2009, 07:06 PM
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I am having a similar problem. i don't think it matters which holes you use as long as you set the pinion angle correctly. I have mine set at a -1 and someone suggested to me to try even lower like -4 for best results while launching. What pinion angle do you have it set at?
coincidentally, I did set the pinion 2* down from the crank centerline angle to compensate for all the polyurethane bushing's flex under hard acceleration.
10-20-2009, 07:09 AM
#4
Hello
Thanks for choosing UMI Performance! The lowest hole is considered the stock location and the hole above will give you more instance center to allow the vehicle to transfer weight faster. And when setting the pinion angle we suggest -2 but some street car set ups like -3. If you have any other questions feel free to ask and I will be more than glad to help.
Thanks
Brad
Thanks for choosing UMI Performance! The lowest hole is considered the stock location and the hole above will give you more instance center to allow the vehicle to transfer weight faster. And when setting the pinion angle we suggest -2 but some street car set ups like -3. If you have any other questions feel free to ask and I will be more than glad to help.
Thanks
Brad
10-20-2009, 08:16 AM
#5
Having the same issue with my adjustable UMI. Went from some modest hook out of the hole with the oem T/A to absolutely nothing with the UMI. Even installed LCA brackets and lowered the rear of the LCA,s - no help. Honestly, I don't see how you can even bolt the T/A to the top hole unless you do it before you bolt it to the rear and tunnel & mine is tapping the tunnel.
There isn't any install info about this, but it seems like front mount of my T/A is forward of the the tunnel mount and those shackels are leaning forward. Should the shackles be perpindicular?
Also, there is another thread on instant center where madman weighed in on the pinion angle and how to set it. Might want to take a look.
Anyhow, if something doesn't give here, I'm going back to the oem T/A and maybe mounting it off the tranny.
There isn't any install info about this, but it seems like front mount of my T/A is forward of the the tunnel mount and those shackels are leaning forward. Should the shackles be perpindicular?
Also, there is another thread on instant center where madman weighed in on the pinion angle and how to set it. Might want to take a look.
Anyhow, if something doesn't give here, I'm going back to the oem T/A and maybe mounting it off the tranny.
10-20-2009, 04:25 PM
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swapping back to the stock torque arm is not an option for me. basically because I cant find my stocker, and it's a limp noodle anyway.
Brad, thanks for the input, I'm going to give the upper mount hole a shot.
it seems like I'm not getting enough lift in the front, and squat in the rear to trasnfer the weight enough to hook.
I'm gonna swap out the competition engineering shocks for a set of low-mileage stockers I have in the garage, swap to the other mount hole, and reset the pinion angle and hope for the best.
street action is just about as common as track action in my area, so I might as well leave it at home if I cant get it to hok on the street.
Brad, thanks for the input, I'm going to give the upper mount hole a shot.
it seems like I'm not getting enough lift in the front, and squat in the rear to trasnfer the weight enough to hook.
I'm gonna swap out the competition engineering shocks for a set of low-mileage stockers I have in the garage, swap to the other mount hole, and reset the pinion angle and hope for the best.
street action is just about as common as track action in my area, so I might as well leave it at home if I cant get it to hok on the street.
07-16-2022, 12:50 PM
#7
Hello
Thanks for choosing UMI Performance! The lowest hole is considered the stock location and the hole above will give you more instance center to allow the vehicle to transfer weight faster. And when setting the pinion angle we suggest -2 but some street car set ups like -3. If you have any other questions feel free to ask and I will be more than glad to help.
Thanks
Brad
Thanks for choosing UMI Performance! The lowest hole is considered the stock location and the hole above will give you more instance center to allow the vehicle to transfer weight faster. And when setting the pinion angle we suggest -2 but some street car set ups like -3. If you have any other questions feel free to ask and I will be more than glad to help.
Thanks
Brad
Ps i know this is old but im worried.
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07-17-2022, 03:14 AM
#9
I have a 3rd gen but the parts are interchangeable so specs are likely the same. Stock specs are the working angle of the u-joints is between 1.0° to 1.5°. And the two u-joints should be parallel within 0.4°. A strong frame-mounted torque arm can be closer to parallel than that, approaching close to 0°. At the end of the day you're going to have to decide how much you think the axle wraps during the majority of your drive cycles. Setup specs in the GM service manual seem to imply that GM thinks the stock setup wraps only about 0.4 degrees (that's the way I'm interpreting it). Cars with stiff springs and strong torque arms wrap less, especially torque arms mounted to frame.
Safe source of info for U-joints is the Spicer media library, https://media.spicerparts.com/media
Search for the words Universal Joint and you'll find application guides. One of those documents is the Driveshaft Installation Guidelines, https://media.spicerparts.com/cfs/fi...store=original
Just a few observations after a quick browse:
Looks like Spicer recommends the U-joint operating angles to be small as possible between 1- 3 degrees, and not less than 1 degree. These are the U-joints themselves, not the parallel between U-joints. I can't quite wrap my head around why the 1° minimum but that's what it says and there's got to be a reason. GM specs for our cars are between about 1.0 - 1.5 degree so that's consistent with Spicer guidelines.
To cancel vibrations they want the U-joint operating angles at each end of driveshaft to be equal within 1 degree. This is the parallel between U-joints and obviously the closer to 0 degrees (perfectly parallel) the better.
The operating speed chart doesn't show specs higher than 5000 rpm but the trend is the higher the speed the smaller the U-joint operating angle has to be. This chart gives insight to where the 3 degree max comes from, looks to be an assumption specific to ~5200 rpm max speed. Well, I don't know about you but I can turn 7000 rpm in 4th gear and that's maybe around 1 degree extrapolating the data?
I also found this document for Driveshaft Application Guidelines and it's a lot more technical, https://media.spicerparts.com/cfs/fi...store=original
Anyway, if you soak up the info in that media library you'll be one of the smartest people on this forum about U-joints!
Safe source of info for U-joints is the Spicer media library, https://media.spicerparts.com/media
Search for the words Universal Joint and you'll find application guides. One of those documents is the Driveshaft Installation Guidelines, https://media.spicerparts.com/cfs/fi...store=original
Just a few observations after a quick browse:
Looks like Spicer recommends the U-joint operating angles to be small as possible between 1- 3 degrees, and not less than 1 degree. These are the U-joints themselves, not the parallel between U-joints. I can't quite wrap my head around why the 1° minimum but that's what it says and there's got to be a reason. GM specs for our cars are between about 1.0 - 1.5 degree so that's consistent with Spicer guidelines.
To cancel vibrations they want the U-joint operating angles at each end of driveshaft to be equal within 1 degree. This is the parallel between U-joints and obviously the closer to 0 degrees (perfectly parallel) the better.
The operating speed chart doesn't show specs higher than 5000 rpm but the trend is the higher the speed the smaller the U-joint operating angle has to be. This chart gives insight to where the 3 degree max comes from, looks to be an assumption specific to ~5200 rpm max speed. Well, I don't know about you but I can turn 7000 rpm in 4th gear and that's maybe around 1 degree extrapolating the data?
I also found this document for Driveshaft Application Guidelines and it's a lot more technical, https://media.spicerparts.com/cfs/fi...store=original
Anyway, if you soak up the info in that media library you'll be one of the smartest people on this forum about U-joints!
Last edited by QwkTrip; 07-17-2022 at 03:22 AM.
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1hotroc (06-27-2023)
07-17-2022, 03:05 PM
#11
It's not complicated. I gave some background information so people have the "safe source" of info and don't have to keep asking yahoos on the internet that are more often wrong than right. Everybody can see for themselves where the requirements come from --- That's the best kind of knowledge sharing. The factory service manual has the correct specs and procedure documented, if somebody can post a copy then that would end all speculation. I referenced numbers from the 3rd gen factory service manual because I have those numbers and it might be the same and gives somebody targets to start working toward.
You can check for parallel on car by taking angle measurements of trans yoke and axle yoke and comparing the two. GM spec (3rd gen) is within 0.4° static with driver in the car. A car like mine with stiff springs, overbuilt suspension links, spherical joints, and high speed capability... I run as close to 0° parallel as I can.
Checking the operating angle of U-joints requires taking another measurement of driveshaft angle and doing a simple calculation for each U-joint. It's assumed the OEM already has this dialed in with the height of the trans mount. But once you start changing ride height and buying aftermarket parts who knows.... sometimes you've got to shim the trans mount up or down to get this number right again. The faster you want to turn the driveshaft the closer the U-joint operating angles need to be to 1.0° (spec = 1.0° - 1.5°). I'm no expert and don't understand why not less than 1.0° but that's the spec and there is a reason why.
Last edited by QwkTrip; 07-17-2022 at 09:08 PM.
07-17-2022, 09:55 PM
#14
You're probably outside spec for parallel. And you don't even have a clue what is your U-joint operating angles because you didn't measure.
It's not complicated. I gave some background information so people have the "safe source" of info and don't have to keep asking yahoos on the internet that are more often wrong than right. Everybody can see for themselves where the requirements come from --- That's the best kind of knowledge sharing. The factory service manual has the correct specs and procedure documented, if somebody can post a copy then that would end all speculation. I referenced numbers from the 3rd gen factory service manual because I have those numbers and it might be the same and gives somebody targets to start working toward.
You can check for parallel on car by taking angle measurements of trans yoke and axle yoke and comparing the two. GM spec (3rd gen) is within 0.4° static with driver in the car. A car like mine with stiff springs, overbuilt suspension links, spherical joints, and high speed capability... I run as close to 0° parallel as I can.
Checking the operating angle of U-joints requires taking another measurement of driveshaft angle and doing a simple calculation for each U-joint. It's assumed the OEM already has this dialed in with the height of the trans mount. But once you start changing ride height and buying aftermarket parts who knows.... sometimes you've got to shim the trans mount up or down to get this number right again. The faster you want to turn the driveshaft the closer the U-joint operating angles need to be to 1.0° (spec = 1.0° - 1.5°). I'm no expert and don't understand why not less than 1.0° but that's the spec and there is a reason why.
It's not complicated. I gave some background information so people have the "safe source" of info and don't have to keep asking yahoos on the internet that are more often wrong than right. Everybody can see for themselves where the requirements come from --- That's the best kind of knowledge sharing. The factory service manual has the correct specs and procedure documented, if somebody can post a copy then that would end all speculation. I referenced numbers from the 3rd gen factory service manual because I have those numbers and it might be the same and gives somebody targets to start working toward.
You can check for parallel on car by taking angle measurements of trans yoke and axle yoke and comparing the two. GM spec (3rd gen) is within 0.4° static with driver in the car. A car like mine with stiff springs, overbuilt suspension links, spherical joints, and high speed capability... I run as close to 0° parallel as I can.
Checking the operating angle of U-joints requires taking another measurement of driveshaft angle and doing a simple calculation for each U-joint. It's assumed the OEM already has this dialed in with the height of the trans mount. But once you start changing ride height and buying aftermarket parts who knows.... sometimes you've got to shim the trans mount up or down to get this number right again. The faster you want to turn the driveshaft the closer the U-joint operating angles need to be to 1.0° (spec = 1.0° - 1.5°). I'm no expert and don't understand why not less than 1.0° but that's the spec and there is a reason why.
https://ls1tech.com/forums/drag-raci...ion-angle.html
07-21-2022, 07:14 PM
#15
TECH Regular
If anyone wants a stock TA let me know. I originally put on an adjustable one and lower brackets but after driving it for a while I got tired of it banging on the tunnel and got rid of it and put stock one back on until I got my 9” and best TA ever the MWC. No noise!
