Losing my mind- pinion angle

[cleetus]

I bought an angle finder and some double adjustable uppers in an attempt to get rid of a vibration that happens around 70mph. I've tried all kinds of different angles from +3 to -5 (positive = nose up, negative = nose down) with some helping and some making it worse. The stock arms had the angle at +4, which caused horrible vibrations and grenaded my old transmission and driveshaft.

The best place seems to be between +1 and -1, but the vibration is still there. I tried many stops in between, with no luck at all.

It can't be tires since they vibration becomes far worse upon coasting, and almost turns into a grinding feel.

The trans is good, motor mounts good, transmission mount good, and drirveshaft new and balanced.

Not that this is the culprit, but there was no problem before having Richmond 410s put in.

Does this all point to a shitty balance job on the DS?

 

[bowtie81]

take the d/s to a machine shop and put it in the lathe and see if it runs true.

 

[TNTS79]

Check the pattern on the ring and pinion... You could have a bad carrier or pinion bearing?? I would stick with around -2 or -3 degrees on the pinion angle. If you have rubber or poly bushings in the control arms, the rear end will tend to rock upwards upon acceleration more so than with solid control arms... You also have to take into consideration the squat of the car which creates more upward pinion travel...

 

[cleetus]

I'm doing the adjustments with the car on the ground, and anything lower than -2.5* is no good at all. It seems to be better closest to 0*.

 

[purple barney]

had the same problem on a mustang a year back, it was the ds thats where i would start

 

[10secBu]

Pinion angle is not the problem from what I read into this.

 

[jrm81bu]

Possible broken flexplate? I had a problem similar to what you're saying with it getting worse when coasting, and that was my problem. And make sure bellhousing bolts are tight. Just throwin out ideas.

 

[cleetus]

Brand new flexplate as well. Forgot to add that got killed in the original problem.

I'm gonna get the brand new drive shaft checked out...If THAT'S the problem, I'm going to be very pissed. If it isn't I'm going to be more pissed...

 

[10secBu]

If the problem did not start till the new gears were installed, then it's time to figure out what changed since then. Grab the pinion yoke and see if it has any wiggle or play like the pinion bearing preload going away or something.

If the vibration didn't start till after the gear swap, then that is a clue (process of elimination) of the first place to look.

Check tire balance...check for bent rims, bent axle flanges, bent axle housing, etc.

 

[cleetus]

There is a possibility the vibration had been there with the 342s @ 100mph, but with 410s it comes on at a lower speed. Still, I'm going to get the DS checked out first.

I was unable to see or find anything out of the ordinary with the pinion, though I'm not sure what to look for. It's in there very tight with no wiggle at all.