Noisy differential

[m3a1]

Gent's we are finally addressing a new issue with my A2 and that is what started as a "noisy" rear differential and by that I mean not just noisy but clearly something is not right. In fact the noise is most noticeable with changes to the loading and unloading of the rear end mostly upon deceleration. So today, my son and I got under there and started checking things. Universal and slip joints on the wheel shafts have been checked, found to be healthy and have been relubricated.

Obvious roblems -
Leaking oil at the input shaft. Rear differential noise is considerably less when there is adequate lubrication. I have a complete seal kit to resolve this. I have removed all the lube and replaced it. There is the usual metallic paste on the magnet but no obvious chrome or metallic shavings and this is something I would expect of a vehicle of it's age.

Left yoke, to which the wheel shaft connects, fairly wobbles on the shaft (whereas the right side does not) yet the yoke's retaining bolt feels tight. However, it is still so cruddy up in there I would have to say there is a possibility that checking bolt tension alone is not a completely adequate diagnosis as the possibility exists that the lock washer could have broken and may be gone. The bolt may be bottomed out and feels tight and yet it appears it is not holding the yoke onto the shaft properly. I just can't get a good look at it at the moment. I will add that the yoke wobbles while the retaining bolt appears to remain stationary which suggests to me that it is not properly seated on the splined shaft.

So my big question is, has anyone else encountered this problem? If so, I would like to hear from you.

Obviously I would rather not tear into the differential for no specific reason and would greatly prefer to sneak up on this problem rather than go in "whole hog." Thus, if the yoke can be resolved externally, that is how I'd rather go about it.

Plan is to remove the differential altogether to do the seals and to better deal with the mysterious yoke issue. I believe I have a proper replacement yoke on the way, just in case.

As an aside, my Alley Cat appears to have an A1 drive-line. Would it be possible to swap out an A1 differential for an A2? Are they interchangeable? If this is a project that "goes long" I would like to be able to keep the A2 up and running until the differential was ready to go back in thus the question about scavenging a differential from the Alley Cat.

Your comments would be very welcome.

Cheers,
TJ

[Mark]

I 'd say the differentials are the same.The only difference between the A1, A2 is the rear suspension,wipers?

[svramselaar]

hi

the diffs are the same
take the front diff from the Cat this one has not run with load (you don't drive much at four wheel drive )

george

[m3a1]

Taking the front is an excellent idea, George. The diff-swap is my backup plan.

I would still like to hear from anyone who may have encountered a similar problem with an apparently loose yoke.

Cheers,
TJ

[rickf]

The loose yoke could have been caused by a bound up axle shaft which would have put a lot of side pressure on the yoke and wore the splines. Be sure to check the axles to be sure they slide in and out easily.

[m3a1]

Thank you. That makes a lot of sense to me, Rick. This truck has had a hard life and it had been making that awful racket since I got it going. While I was under there I was giving everything a good, forceful tug which is how I discovered the wobble in the yoke. Because of that yoke, we removed the whole left axle shaft for servicing. It is capable of sliding in and out but I would describe it as being rather stiff when compressed or extended by hand.

The right axle shaft had a shiny spot that indicated sliding movement in the shaft, whereas the left never did (which is something I now know I should have been looking into far earlier.) Anyway, when the new yoke arrives, we'll pull the differential and both axle shafts and give everything a good going over.

My son had a new experience when we were taking the left axle shaft out. I warned him that it was very important to keep those caps on the universal joint, he being at the spindle end and I being at the differential end while getting everything undone. Well, he neglected to keep an eye on it, a cap came off and there were quite a few needle bearings to pick up. The kid looked like Ralphie losing all the lug nuts in the movie, A Christmas Story. "Oh FUuuuuuuDGE!" Except he didn't say that.....



Thanks to ol' Dad, (the guy who won't start an automotive job in the driveway without first clearing the area thoroughly with a leaf blower) those bearings didn't get far. So, we had to stop everything, gather up all the bearings, give everything a wipe-down and put everything back together. Having had that experience, I'm sure he'll be more careful next time and he won't look at me with such disdain for taking the extra time to prep the work area. This is just another reason why Old Guys Rule!

This story isn't over yet. There may be more to discover once we get into it and I'll wrap this up then but for now I'll simply say, thanks for the input!

[rickf]

Oh, Been there done that many times and on a floor that had hundreds of needles from many different u-joints. Now THAT can get interesting. And it always happens late at night when the vehicle is needed the next day and you have no spares.

[Barlow L]

There is a very well written tutorial on the G503 site about rebuilding the MUTT diff's by Armybuck041.

This is a quote from his write up that may shed some light on your question

"Things I noticed prior to Teardown:

A couple of my Flanges/Yokes were slightly loose on the Shafts prior to teardown, but yet the Bolts seemed tight. When I pulled everything apart, I found the cause which probably contributed to leaks as well. Inside the Yokes there was a bead of RTV from the Factory probably to prevent leaks via the Splines and out around Yoke Bolt. Whats happened is after nearly 30 years, the RTV was as hard a super old plastic and had either contracted and cracked or started to break into small pieces and allowed the fit to loosen up. After thoroughly cleaning all of the RTV gunk out of the inside Yokes, I reinstalled them on the Carrier, and voila, they were nice and snug again. If you are having problems with what feels like a sloppy yoke, check for this condition first. If so, simply clean thoroughly and apply new RTV and reinstall. I wouldn't be surprised if many owners around here are getting their leaks this way and no through the larger seal itself."


Lee

[m3a1]

Thanks Lee. I did my research here on the site, found that link and already read that but, the tutorial didn't explain the hows and whys of a loose yoke. My axle seals aren't leaking but that RTV tip is certainly going to be an important point for installing the new flange.

I think Rick's explanation details the most likely cause and frankly, I'm betting I'm going to find that the lock washer split (it is, after all, the weakest component of the whole thing, and I'll bet it worked it's way out creating a gap between the bolt head and the flange, thus allowing the yoke to wobble. That's my theory, anyway.

I hope that retaining bolt is still sufficiently intact that it will allow me to back it out without a lot of fuss. It has (potentially) taken a beating. We shall see, and let's all hope I don't have to get inside the differential because I have a half track just waiting to gobble up all my spare $$$$.

Cheers,
TJ

[fergrn37]

I also have leaks and one 'loose' flange. But mine was cause by a frozen U-joint that also cracked a drive spindle. So spindle, U-joints all around$$$, and when I get around to it seals for the diffs and a new side yoke. Such a party here!

[m3a1]

I feel for ya. Considering the ease with which these could be maintained (all ya have to do is get down on the ground!) I'm surprised these are so abused but "out of sight, out of mind" I suppose.

[Auzziemutt]

What's an alley cat, another version of the152?

[rickf]

There were several aftermarket companies in the 80's and 90's making bodies and using all the M-151 running gear. Titan was one of them. Encore is the most well known and there was Growler and at least one more I can't remember the name of. These all had real frames and welded steel bodies and were much better built than the originals. Then again, they were not built within the restrictions of the military contract of weight and cost.

[m3a1]

Exactly. Go here to see my Alley Cat -

http://www.g838.org/viewtopic.php?f=2&t ... cat#p32760