svrider76

On the highway at around 60MPH and above (lessens closer to 70MPH and peaks at 65MPH) my Firebird makes a vibration/rumbling noise which seems to come from the rear. At around 65MPH the noise is most prevalent and almost sounds like drum beats or pulsing (musical instrument not brakes).

Recently the rear end oil was changed, and today i did notice the pinion seal is throwing oil (I did read what was involved in the sticky on replacing bearings/seals), I am not sure if this pinion leak is related to my noise or if the leak is more noticeable now that I just got done an extended highway drive.

The vibration noise does seem to respond to throttle load, and I can almost cancel the noise out under very light throttle.

Any thoughts?

Things to note: 1) there were some small metal filings on the diff cover magnet and there was a small half "c" shaped piece of metal. This cant be normal, but could this be a shim that came loose or possibly a clip?
2) The car was recently worked on over the winter which involved pulling the engine and transmission. Would it be an issue if the drive shaft was installed 180 deg out of position?

big gear head

The easiest thing to check is the u joints in the drive shaft. Also check the pinion bearings by holding the yoke and pushing up and down on it. Also push in and out. If you get any movement at all then you have a problem with the pinion. Many times it's just a loose pinion nut. If the nut is tight then you need to tear it down and replace the pinion bearings. The pinion seal leak points to the pinion bearings.

svrider76

Thanks for the input. I will check for play tomorrow and see what Ive got.

svrider76

Okay, got under there today. I did not feel any play in the u-joints both front and back. I do know that they are at least a second set because both have the metal snap ring retainers and not the nylon factory filler. Still does not mean they are good or not, but i did not feel any play.

The differential pinion has rotational play (clock wise/ counter clock-wise) with respect to the diff. I would guess about 1/16-1/8". The Drive shaft would move with the yoke. No up/down or in/out play on the pinion.

Is this normal play (free play in the differential gears, what is the gear that is attached to the yoke?) or is this abnormal?

big gear head

I would start looking at bearings. Could be a differential bearing. The seal may be leaking just because it's bad and might not have anything to do with pinion bearings. I did a WS6 Trans Am rear end a few months ago that had a similar noise and it was the left differential bearing.