'89 M998 poping when accelerating in a straight line.. diff?

[ke6rwj]

We've been driving this truck for a while and no real issues. We started getting popping on turning, but recently its also started popping rapidly when accelerating forward and backwards. I replaced all 4 axles with new ones and it still pops. Its a rather fast pop also, sounds like its in the rear. My instinct based on the sound its in the right rear.

Here's what I've done.
- Replaced all 4 axles with new ones
- Checked for loose brake caliper/pads/bolts
- driveshaft joins seem tight, nothing obvious in suspension
- drained rear diff oil nothing major on plug or came out with fluid. Just very fine dust on the plug.
- no leaks to speak of..

Is it possible the diff / ring pinion is slipping?
Other possibilities?

Thoughts?

-- Chris

 

[DREDnot]

I would chock the wheels and drop the diff end of each driveshaft so there is no load on it and then check(and grease ) all the u-joints. Often the u-joints will seem good when installed but are in fact seized or wollered out and it is only noticeable when one end is removed.

If all is good there then jack up each diff in turn and give it a few turns to check for shenanigans while its isolated from the drivetrain before reinstalling the driveshaft

 

[Gcelevator]

Pillow bearing in the front drive shaft?

 

[ke6rwj]

An update on this issue...

- I removed the covers from the rear geared wheel assemblies and all were fine, teeth look great, checked the splines, all good and no metal at all.
- removed the cover from the diff and everything there looked great.
- Greased the drivelines and u-joints in case they were sticking

The real eye opener was that the transfer case was dry...

looking at our service records for this truck showed that it was checked 2 years ago, but prob not since then... They don't get a lot of use, only 1500 miles since the last check.. regardless, it is dry.. I filled it and rechecked everything, its the same..

it pops when you put the drive train under load, like accelerating up a hill, from a stop or trying to drive over a brick. Its equal in D, 1, 2 and R and H or HL makes no difference.

At this point unless I find a stripped yoke, it seems like the Transfer is smoked.. Im gonna drain It and peek inside with a scope to see anything obvious, but honestly I can't imagine what else It could be..

thoughts? comments?

-- Chris

 

[TOBASH]

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