Pinion Angle - Inexpensive Fix
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Junior Member
Joined: Oct 2006
Posts: 84
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From: Connecticut
Car: 89 Formula
Engine: LB9
Transmission: T5
Axle/Gears: 9 bolt / 3:45
Pinion Angle - Inexpensive Fix
Needed to adjust the pinion angle on my Formula, because the car had a vibration problem, and during troubleshooting we measured too much of a negative pinion angle (-2.8) , not ideal for street use with a torque arm (according to what I have read). The Factory service manual method to correct pinion angle is to shim the transmission mount, which I did, could only take out about 0.6 degrees before the Y-pipe had interference issues with a subframe rail. I still wanted to go a degree more, but had no way to move the transmission / torque arm pivot higher.
Looked at getting an aftermarket adjustable torque arm, but was put off by the price and reported install issues. I really did not need the extra strength or mount relocation of the aftermarket units, plus, people have reported clearance problems with some of them. I had an idea that worked out pretty well and was best of all cheap, and took about ten minutes.
I was able to place “shims” in-between the rear end housing and the stock torque arm, which effectively rotated the housing inside the torque arm and get the remaining degree of adjustment I was aiming for.
The fix used 0.064” thick 7/16 washers with the holes enlarged to 0.530" as the shims. One was placed on the bottom front of the housing, and the other was placed on the top rear of the housing. The through-bolts go through the washers. There is some “give” to the fit of the stock torque arm, so it was not too hard to slide the washers in between the arm and the housing. One through-bolt was removed at a time, leaving the other slightly loose, to prevent the torque arm from coming off the housing while the shims were added. Also, it was done with jackstands supporting the body, with the rear end springs unloaded. Do not mess with the torque arm with the rear suspension loaded, there is a lot of force in a loaded suspension.
For $0.40 worth of washers we can "adjust” the stock torque arm for pinion angle in less than 15 minutes.
Looked at getting an aftermarket adjustable torque arm, but was put off by the price and reported install issues. I really did not need the extra strength or mount relocation of the aftermarket units, plus, people have reported clearance problems with some of them. I had an idea that worked out pretty well and was best of all cheap, and took about ten minutes.
I was able to place “shims” in-between the rear end housing and the stock torque arm, which effectively rotated the housing inside the torque arm and get the remaining degree of adjustment I was aiming for.
The fix used 0.064” thick 7/16 washers with the holes enlarged to 0.530" as the shims. One was placed on the bottom front of the housing, and the other was placed on the top rear of the housing. The through-bolts go through the washers. There is some “give” to the fit of the stock torque arm, so it was not too hard to slide the washers in between the arm and the housing. One through-bolt was removed at a time, leaving the other slightly loose, to prevent the torque arm from coming off the housing while the shims were added. Also, it was done with jackstands supporting the body, with the rear end springs unloaded. Do not mess with the torque arm with the rear suspension loaded, there is a lot of force in a loaded suspension.
For $0.40 worth of washers we can "adjust” the stock torque arm for pinion angle in less than 15 minutes.
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