Driveline/Pinion Angle and Vibration HELP
. Basically (if you cant tell from my sarcasm) I'm about ready to blow my car to pieces with lots of explosives so help me please 
btw I have gone through every other possibility (wheels/tires/brakes/ujoints/crank pulley/clutch/etc) It starts at 60mph and gets worse the higher speed I go and is much worse when I am coasting as compared to when I am on the gas. Here is a diagram that I drew up myself on the angles for which I have measured.
The car was lifted by the rear axle, suspension loaded, rear end in the air, front on the ground.
And yes, I know its completely wrong. It was different before, but when I had an alignment done, I told the guy to set my pinion angle at -1 to -2 degrees just in case the planets aligned right and it fixed my problem, but of course it didn't.
I'll be here waiting

However, I suspect your vibration may be due to your poly motor / engine mounts vs. the rear end / pinion angle setting.
Having said that, the only way to test this theory is to replace the engine's poly mounts with stock units then check for a vibration again; yeah sorry.
Here is a diagram that I drew up myself on the angles for which I have measured. The car was lifted by the rear axle, suspension loaded, rear end in the air, front on the ground.
And yes, I know its completely wrong. It was different before, but when I had an alignment done, I told the guy to set my pinion angle at -1 to -2 degrees just in case the planets aligned right and it fixed my problem, but of course it didn't.

First go to Sears and buy the $25.00 magnetic digital angle finder that reads to the .1 of a degree. The one with the rotating needle is ****.
1. Put the front wheels on ramps or the front chassis on jackstands.
2. Put jackstands under the rear axle tubes.
3. Make sure the entire car is supported well and mostly level to the ground.
4. Place the angle finder (AF) on the front VERTICAL face of the harmonic balancer. Record the reading.
5. Place the AF on a VERTICAL surface on the rear end.
6. While adjusting the torque arm, set the AF to the exact same reading recorded in step 4. The crankshaft/tranny and pinion should now be perfectly parallel.
7. With the AF still on the rear end, again note the reading. Adjust the torque arm so the pinion yoke slowly rotates down toward the ground. You want to lower it 2 degrees compared to your original reading.
8. Tighten down the torque arm.
9. Drop it and dive it. You now have dead nuts on negative 2 degree pinion angle.
If the vibrations are still there, the drive shaft is out of balance. I have been down this road. I feel your pain. Follow these directions and wrap this bitch up.
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Looks like the trans tailshaft and front pulley are approximately 1* off from each other, not sure this is normal. Now when setting the rear pinion you're saying I should base it off the front pulley and should set it at a 6.2* angle correct? As of right now it is at a -0.1* angle according to the pulley and a +0.7* according to the tailshaft. Car is somewhat level now as both the front and rear are raised. Thanks for the help
Any possibility that I am going beyond the ujoint operating angles? Maybe I should consider shimming the rear of the transmission
Last edited by Jimmard; Aug 6, 2009 at 03:39 AM.
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Looks like the trans tailshaft and front pulley are approximately 1* off from each other, not sure this is normal. Now when setting the rear pinion you're saying I should base it off the front pulley and should set it at a 6.2* angle correct? As of right now it is at a -0.1* angle according to the pulley and a +0.7* according to the tailshaft. Car is somewhat level now as both the front and rear are raised. Thanks for the help
Any possibility that I am going beyond the ujoint operating angles? Maybe I should consider shimming the rear of the transmission
Once you have the exact same readings on the balancer and at the rearend, rotate the pinion yoke down toward the ground 1.5-2 degrees according to the AF. It will now be set.
Ideally you want 3 degrees or less operating angles on the u-joints for long life and less parasitic loss. If you have even 4 degrees (which I doubt you will) its no big deal. As long as both joints angles are equal or +/- 1 degree to each other, you will NOT have angle induced vibrations. Both u-joint angles being closer to equal trumps operating angle. I once ran 13 degree operatring angles on my Jeep Wrangler and had no vibes since they were 13 degrees on both ends.
I found on my 9" I had to raise the tranny 1/2" with spacers (off of the tranny mount) in order to get closer to equal angles on both joints. This did cause my operating angles to go about 2.5 degrees which is no big deal. The 9" has its pinion around 3/4" lower than the 12 bolt and 10 bolt so that has to be tweaked for optimum setup.
Last edited by wrd1972; Aug 6, 2009 at 12:39 PM.
You might have the area just outside the seal but behind the dust cover filled with fluid. Put some miles on it before going after the bushing again.
You might have the area just outside the seal but behind the dust cover filled with fluid. Put some miles on it before going after the bushing again.
if it changed when you took out/reinstalled the trans, i think you still have a drive line angle problem. try putting a washer or 2 under the trans mount
if it changed when you took out/reinstalled the trans, i think you still have a drive line angle problem. try putting a washer or 2 under the trans mount




