front differential noise, only when accelerating (WITH PICTURES)

[MannyDantyla]

Hi all

I'm getting a pretty nasty sound coming from the front differential. I have a GM 10 bolt up front, low pinion. It ONLY make the noise when accelerating!  And it only happens when both in 4L or 4H and hubs are locked, both conditions have to be met. It doesn't sound like a hum, it sounds like a grumble but pretty bad. It gets louder the faster I drive starting around 15mph and at 40 I don't dare go faster than that.

I checked to see if the pinion nut came loose and no, it's good. There is however just the tiniest bit of play in the yoke when I grab it and try to push it side to side. Could this mean the the pinion bearings are bad? If so, could I replace just the outer pinion bearing without taking the diff all apart? Just not interested in putting money and time into this right now.

Thanks!

[Captkaos]

I think you need to inspect it internally and find the source.

Chris Lucas
73-87chevytrucks.com
squarebody.biz

[MannyDantyla]

I think you need to inspect it internally and find the source.

I think you're right.

[MannyDantyla]

Anybody see anything wrong??

[VileZambonie]

So with the transfercase in 2WD and the hubs locked it doesn't do it?

[MannyDantyla]

So with the transfercase in 2WD and the hubs locked it doesn't do it?

Exactly

I just put fresh gear oil in it (old oil looked fine, no metal flakes) and drove it around the neighborhood in the snow and I brought my roommate with me for another set of ears. At first he said is just sounded like noisy gears but after a while he agreed that it sounded a little rough. We think it might be a  dry bearing somewhere.

I should say that I've had this problem for a while now. Except that it didn't always do it when only accelerating, it used to be only audible when coasting to a stop! Here's a video I made last year:
https://www.youtube.com/watch?v=bM4PNRdTTdU

[youtube]bM4PNRdTTdU/youtube]

When I had the cover off just now, I grabbed the pinion from inside the pumkin as best I could and tried to find any lateral play in it but there was none. Everything looked solid! A little rust on the spider gears maybe, but I don't think this noise is it shaking off the rust (no pun intended). It's been getting louder over the years.

[VileZambonie]

Check the front driveshaft. Also lock it in with the front driveshaft removed to see what it does.