My Jeep howls when decelerating

I have a '96 that for some time now howls while decelerating from about 35-15mph.
Doesn't do it right away, it starts after its warmed up well.
Not sure where it is coming from.
It does the same in both 2WD and 4WD.
Any ideas?

Possibly pinion bearing? Mine did this after the lift and before pinion angle was corrected. Is yours stock and just started this?

riverfever said:

Possibly pinion bearing? Mine did this after the lift and before pinion angle was corrected. Is yours stock and just started this?

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No lift.
It started a few months ago.
Previously the rear diff had bad pinion bearings and I found out while I was replacing the diff with a Truetrac. I had a pro replace the pinion bearings and also check my work. He found no problems.
Later I replaced the front diff with another Truetrac and everything seemed to go well. Didn't get any noise for 6 months or so.

falcon556 said:

No lift.
It started a few months ago.
Previously the rear diff had bad pinion bearings and I found out while I was replacing the diff with a Truetrac. I had a pro replace the pinion bearings and also check my work. He found no problems.
Later I replaced the front diff with another Truetrac and everything seemed to go well. Didn't get any noise for 6 months or so.

Click to expand...

That does sound like a pinion bearing though. I'd get under the jeep and check the yokes for a little bit of play, just to be safe. It may be necessary to unhook the driveshaft to really feel it. I bent a driveshaft just a hair about six months ago and had it take a pinion bearing out on a rear end that was nearly new.

cal said:

That does sound like a pinion bearing though. I'd get under the jeep and check the yokes for a little bit of play, just to be safe. It may be necessary to unhook the driveshaft to really feel it. I bent a driveshaft just a hair about six months ago and had it take a pinion bearing out on a rear end that was nearly new.

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The pinion seal seems to be a little wet, if the pinion bearings are the problem,
I could open it up and replace all the seals and bearings.

falcon556 said:

The pinion seal seems to be a little wet, if the pinion bearings are the problem,
I could open it up and replace all the seals and bearings.

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If you are confident you can do it yourself, try it and see what happens. Check the driveshaft to be sure its true too, and in balance. Throw some jack stands under the rear axle and run it up to 15 mph or so, watch the shaft.. see if there is any play. If the pinion failed, there is probably a cause..

-C

cal said:

That does sound like a pinion bearing though. I'd get under the jeep and check the yokes for a little bit of play, just to be safe. It may be necessary to unhook the driveshaft to really feel it. I bent a driveshaft just a hair about six months ago and had it take a pinion bearing out on a rear end that was nearly new.

Click to expand...

When the pinion bearings went bad in the D35, I was able to push and pull the yoke and feel quite a bit of movement.
I just went under the Jeep and tried both front and rear yokes by hand and also using a screwdriver for leverage, no movement.
The D30 pinion seal is wet, unless somebody can point me a new way, next week I'll pull the guts out and replace the pinion bearings if not all, run a tooth contact pattern and check the backlash.