Mutt Diff, Reparable or Junk?

[rickf]

You don't really need to go all out with a bearing to hold the yoke in. All you need is a piece of metal bent so that it clears the ears of the yoke and has a point on it to contact the center of the yoke. And then find a place to bolt it so that it stays in that position. It does not have to press on the yoke, it actually would be better to push the yoke all the way in and then set the point about a quarter inch out from that. That way when the yoke slides out it touches the pointer and does not exert and real pressure on it. Job done. This is along the lines of what was done on the very early straight 151. You could also keep a spare yoke ground down so that a flat plate would work, less fabrication that way.

[lpcoating]

Here are pictures of the failed diff. I see nothing obvious. Bearings feel fine, gears look as I think they should. This thing sounded like the back of the truck was about to fall off and was extremely hot. And yes, it had oil. Fresh oil at that.

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Guy

[rickf]

I see a lot of metal flake in that oil and the ring and pinion both look pretty rough on the wear surface. The carrier bearings do not look bad but what about the pinion bearings? That oil is telling me that a bearing failed somewhere in there. Or the surface on either the ring or inion is failing. I have only ever seen that one time on many hundreds of differentials I have done but it does happen.

[rickf]

After zooming in on those pics, especially the bottom one and the ring gear, I can see a TON of metal in the oil and the gears are completely gone. I looks like the pinion was set too deep to begin with unless the pinion bearing is what let go, which I kind of think may be the issue. It is junk as it sits. You need a new ring a pinion, all new bearings and seals and might as well throw in a spider gear set since that seem to be a weak spot on these.

[m3a1]

The problem with NOS is....it is just a word.

On this site we have occasionally discussed parts that had been discovered by someone and distributed as NOS which in actuality, turned out to be parts that were manufactured, found to be out of spec, and refused. Those same parts, rather than being scrapped, somehow made it into storage, probably with the idea that they would eventually be remanufactured. And they (and their circumstances) were forgotten.

Waste not. Want not. (usually)

Except eventually, they were rediscovered and someone put them on the market not knowing what their provenance was. Also, one occasionally just gets a klinker.

Ya puts yer money down and takes yer chances!

In Afghanistan, when some boob blew himself up prematurely (meaning, no one got hurt) we would often discuss the benefits of receiving 72 virgins for all that trouble. The general consensus was, it would be far better to receive 72 barmaids. So, personally, I would rather receive a proven, used differential; give me one with some experience and not just a pretty face.

Cheers,
TJ

[lpcoating]

Looking at it some more the ring gear is sharp. As far as the NOS comment, this was in the original box packed in foam. I'd think if it was a rejected part that somehow made it out of the factory, it wouldn't have been packed. Clearly it was not built to spec. Again, this diff has less than 2,000 miles on it.

[rickf]

That was either preload to tight or pinion too deep. You can see where it started out higher up and moved down but it took a massive amount of metal off of the back of the gears.

[Lou]

Thanks for the photos. Please open up the carrier and show us the condition of the spider gears, especially the thrust washers. Agree with Rick about the pinion to ring gear mesh.

On another note, may have a reason my diff failed. When my axle shaft broke the week before, pulled that shaft off. Drove the mutt about 10 miles home with the other shaft still connected. There was a very loud whirring noise on the way home. That loud noise was the yoke for the axle drive shaft on the diff spinning a million miles per hour because no shaft was connected to it.

Think about it. Normally the carrier and the axle shafts spin roughly the same speed unless going around a turn. So with only one 1 axle shaft connected to the diff, the side without the shaft was turning like hell because there was no load on it. With no bearings in the carrier, supporting the shaft driven by the spiders, probably wore the housing out.

Too much of a coincidence to rule this out. That seal never leaked a drop of oil until after the axle shaft failure. With the diff out found the excessive axle shaft to carrier play.

[rickf]

Lou, Wouldn't work that way. You still had the drive shaft in and one axle. PLUS you were in 4 wheel drive. SO, you were driving down the road at normal speed with the rear drive shaft also doing normal speed along with the remaining axle doing normal speed. The fact that you were in 4 wheel drive there was zero load on the back differential so the spider gears would not have been moving at all.