Driveshaft/pinion flange run-out measurement after gear change?

Hello,

is it necessary to do a pinion flange and cv joint run-out measurement and adjustment after pinion change?
I have a speed related vibration in the rear end after 3.73 gear install from 75 to 80 mph.

Thanks!

Go back and double check the driveshaft center mount bolts and the pinion flange hardware for a start.

RocketcarX said:

Go back and double check the driveshaft center mount bolts and the pinion flange hardware for a start.

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This. You should not have to check Pinion Flange Run Out if the proper install procedure was followed for Pinion Torque.

Thanks,

I was able to tighten one center mount bolt 1/8 turn to get torque spec, no change. Pinion flange bolts are ok, but I reused them several times. Weight is mounted on the driveshaft.

Pinion Preload was 18-20 in lb
The strange thing I noticed was a different preload between forward and reverse rotation. The reverse turn resistance was a bit higher (new bearings, new seal). That was only the 3rd rebuild I have done so no real experience.

If there is run-out on the pinion flange, it would mean that something like a bearing race was not properly seated as I can't think of any way that you could adjust the run-out of the pinion flange short of replacing the housing or the gearset.
Did you mark the driveshaft and pinion flange before removing it? If you didn't try re-clocking the driveshaft 90 degrees at a time to see if it improves.

Yes I marked the driveshaft and the flange before removing it. There were also some paint marks from factory. But I can try to rotate the shaft 90 deg anyway to see what will happen.

I think I seated the races properly. The bigger race I measured with a feeler gauge.
I also replaced the stock lca with the J&M extreme, can they produce a rear end vibration?

The lower usually do not. The upper sometimes can-but that is usually due to another problem being amplified. In my case, it was simply the rear tires needing to be rebalanced, others have chased pinion angle, etc...

Check the brakes and wheels next

I will check the brakes and tires next. I agree that rubber bearings on lca/uca/panhard only masks problems, same for the iron vibration dampers.

Thanks

You can also check the drive shaft center carrier bearing mounted in rubber that its not flapping around. If the rubber is getting old it will let the bearing housing move around.

travelers said:

You can also check the drive shaft center carrier bearing mounted in rubber that its not flapping around. If the rubber is getting old it will let the bearing housing move around.

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Some time ago the workshop removed the driveshaft to replace the transmission output shaft oil sealer. They fixed the bracket of the center bearing with tension. When I removed the bolts, the bracket jumped immediately to the tension free position. Noise gone.