Differential

[dr. trinkmann]

Guys, another question from semi-newbi:
Are the differentials known to go bad over the time?
With my vehicle there is a noticeably howl from the rear especially with higher Speeds.
Unfortunatelly i have no sound comparisation to other Mutts jet.
Is it worth to buy a new, original and boxed "in foam" differential to keep it in stock for 300.- Euros?
Should i get i or leave it?

Thanks for your advice.

[halftracknut]

They all make some type of noise...this is normal....

[raymond]

The differential is bolted directly to the unibody. There are no rubber bushings. The differential is directly beneath the rear floor. The rear floor acts like a speaker and transmits the sound and vibrations directly into the vehicle. Two things to try before buying a new differential. One is to switch it with the front differential. The front is typically not used much so will have less wear and tear. The other is to put a heavy rubber mat in the rear floor board.

[gcbennet]

What’s the professional opinion on installing aftermarket bushings? Theres been a modest amount of chatter on various venues on this particular subject with mixed feelings. I, for one would certainly enjoy driving my A2 much more if I could actually have a conversation while driving at higher speeds.

[rickf]

What’s the professional opinion on installing aftermarket bushings? Theres been a modest amount of chatter on various venues on this particular subject with mixed feelings. I, for one would certainly enjoy driving my A2 much more if I could actually have a conversation while driving at higher speeds.

This is a subject that is like "what is the best motor oil". In order to isolate the rear differential from the body you need to do a bit more than add a couple pieces of rubber between the diff and the mount. You have to totally isolate all metal to metal contact. Remember that you have a metal bolt running through the differential and the body mount. That bolt is going to transmit just as much noise as if the rubber pads were not there. So what you would have to do is to drill the holes in the differential oversize and find rubber mounts that extended down through the holes to isolate the bolt from the diff, then you also nee to isolate the top of the bolt from the diff so rubber and washer between the bolt head and the diff. So, Now, you finally have all kinds of fancy rubber mounts and modified holes and your differential is completely isolated from the body and it is nice and quiet. NOW, you will find that you are probably going to tear the rear mount off of the body since it was never made to handle the constant movement from the diff which is mounted in rubber.

Bottom line, These are tactical vehicles that were made for military use and not leisure cruising. They are loud and minimalist.

If you really want to modify the rear diff mount to a quiet setup that will work as intended and also last get in touch with George from Holland. He designed a rear mount from one off of a Volvo or Mercedes and it is a sweet setup.
Here is his contact info, send him a pm and tell him what you are looking to do.

memberlist.php?mode=viewprofile&u=82

[m3a1]

Absolutely correct about that floor being a big speaker and this being a monocoque body, sound will transmit to other parts of the body which will also resonate IF the floorpan directly over the diff is allowed to resonate. Minimize the rear floorpan resonance and you'll be well on your way to minimizing the noise overall.

So, the FIRST thing you do is get a big bag of something (like a bag of dog food or what have you) and put it on the floor above the diff and I guarantee you WILL see a big difference. "Howling" is the word most often used to describe the noise from these differentials (even those in good health) and so, is not necessarily an indication of a problem with the unit itself. No matter how healthy or unhealthy a differential may be, there will be noise transmitted to the body. It is the nature of the design. If you want a nice conversation whilst enjoying the autumn foliage, just slow down. If you're going hell-bent-for-leather (which you shouldn't be) again, slow down. These trucks have more in common with farm tractors than automobiles.

As to the health of your differential, let us not forget that much is going on down there, including axle drive shafts, all U joints and so on, all of which have to potential for contributing to the noise transmitted up to the body through the differential. So, the SECOND thing you need to do is get under there and pull maintenance with your grease gun and don't forget to check those axle bearings....the whole lot. These all have a potential for contributing to noise.

Throwing money at your truck for a NOS differential which may very well be a rejected rebuild (and the very reason why it's still found to be crated at this late date) is not necessarily going to solve your problems. There are no absolute guarantees unless, of course, you find a seller who makes you an absolute guarantee. If you feel you absolutely must be rid of that rear differential, swapping diffs, front to rear is a very sensible first step before dropping big bucks on a Hail Mary fix.

You will find plenty on the maintenance issues under the following (much of it several pages into the project) - viewtopic.php?f=27&t=8354

Cheers,
TJ

[Horst]

My jeep has now still less than 6.000 miles since new. It is loud. So I am pretty sure that new differentials will not solve your problem satisfactorily. Unless you have really bad ones.
In addition to what TJ said, the transfer part of the transmission is another good source of noise which transmits through the whole unibody. In my case the gearbox is the only part not original to the car, it is a used take-out. I went through the transfer and rebuild it with new or good used parts and that did cut down the noise significantly. Specifically when coasting under light loads.
Apart from that I also do have 2 NOS differentials in the foam box but I am almost certain I will never need them.

[halftracknut]

I just love this subject ...I bought my last A2 with a NOS rear end...I screamed ....so I bought another NOS from blake at Red River and same same....Ha the joke was on me.....Just like Rick said...your in the Army now get used to it.....













nos

[acudanut]

Well there is loud and screaming loud. I replaced mine because I knew from experience it was shot. I replaced it and wow am I happy now. (my 2 cents)
I have 2 laying around in my garage that I think need attention. Any buyers out there ?

[dr. trinkmann]

Thank you gentlemen for your interresting answers.

[m3a1]

You might also want to check the level of the lubricant. Just sayin'.....

[Barlow L]

I recently repaired the beat out body mounts where someone had installed 1/4" rubber spacers. The forward spacer lasted no time and with that 1/4" gap, it jackhammered the body.
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