exchange diffs

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exchange diffs

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exchange diffs

Postby Auzziemutt » May 5th, 2016, 3:00 am

I have a noisy diff ,would you believe, but only in fourth gear under load. The diff man took it apart and said it was perfect, like new, so now I want to change over the front and rear diffs and see if that is any better. I read somewhere that they are interchangeable. Is that so and is there anything I should be aware of or just a straight IN-OUT- and on your way job. Does it help to add super thick oils like STP (do you have that). It looks like treacle. Col
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Re: exchange diffs

Postby 199th mp » May 5th, 2016, 6:21 am

yes, they are identical and a straight swap. we have STP, though i never put any in the differential. i tried as best as possible to follow the lube order to the letter. since yours is in good condition, it is possible that the rpm's are hitting a note that vibrates the sheet metal of the rear floor. i did an experiment once on mine, placing several heavy bags of sand on the rear floor, just to test this idea. with the sheet metal thus dampened, most noise went away. pity we can't drive around like that, eh?
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Re: exchange diffs

Postby nobby » May 5th, 2016, 10:46 am

I thought my gearbox had a problem in 4th as it also sang like a dieing diff.
As 3rd was really buggered i swapped the gearbox. The noise in 4th remains the same.
I then was leaning towards the diff but i have since decided its just a harmonic resonation that happens to manifest as the lower end of 4th gear.

Have now decided its just the nature of the beast.
If it was a normal car id turn the radio up..
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Re: exchange diffs

Postby Horst » May 5th, 2016, 11:44 am

These differentials are noisy to begin with. When I got my truck, it had 86 miles on the odometer and it was already noisy.

BTW, a worn transfer is also making a lot of noise. Both the needle bearing at the brake drum and the intermediate shaft make noise when worn. Noise in my truck did go down considerably after I overhauled the transfer. viewtopic.php?f=3&t=9242
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Re: exchange diffs

Postby Auzziemutt » May 5th, 2016, 6:52 pm

Hmmmm, So if I load up some sand bags and install a car radio I'll be able to hear my wife nagging me about how noisey and bumpy my baby is ! Decisions decisions . Come on in Rick and Dan, you know everything.
I jacked up a rear wheel and ran it in top gear and used a stethoscope to listen to the rear end but no bad noises so I put the pick-up on the gearbox and it was quite a good even noise as I would expect. It's exasperating isn't it. Does anyone out there have a 151 that doesn't have the same problem.
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Re: exchange diffs

Postby Auzziemutt » May 5th, 2016, 6:54 pm

Nobby that's really disheartening what you wrote.
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Re: exchange diffs

Postby kmam » May 5th, 2016, 7:23 pm

Might be time to offer for sale a MUTT noise reduction kit: six sandbags and instructions :)

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Re: exchange diffs

Postby raymond » May 5th, 2016, 9:35 pm

A heavy mat on the rear floor goes a long way toward quieting the noise.
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Re: exchange diffs

Postby 199th mp » May 6th, 2016, 7:52 am

kmam wrote:Might be time to offer for sale a MUTT noise reduction kit: six sandbags and instructions :)

Howard


step 1: get a sandbag step 2: place on rear floor step 3: repeat five more times step 4: put IPOD buds in ears step 5: ignore passengers screaming at you to slow down step 6: accept the fact that life is short, have fun.

well, you said you wanted instructions. i copied this from the official us army manual. really. honest. would i lie?
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Re: exchange diffs

Postby rickf » May 6th, 2016, 8:09 am

Sorry Auzzie, Don't have a lot to offer. These are noisy little critters so you know. I had a diff go out on me, puked out a seal and ran dry before I even knew it so I was driving with no oil in it. It was glowing by the time I got home and it was screaming. I put in a rebuilt one I had and it was nice and quiet...................... for a couple weeks and right back to the usual noise. As has been said though the transfer case bearings can mimic the sound of the rear so you may have to look there also. And when you were listening to the rear did you only have one wheel in the air? That would not have been good in high gear! That would mean the tire in the air was spinning at roughly 120 MPH!!!!! That would be because the spiders in the rear would be doubling the speed of the one tire turning with the other stopped. Always jack up both sides and support under the outer ends of the control arms so that the axles are not drooping. You are not going to hear any noise from the rear when it is spinning with no load. Go down the road listening to the noise and then push in the clutch and pop it in neutral and shut it off while coasting at 50 MPH. Now listen for noises and see what you hear. If you have the military NDCC tires then that is most of the noise.
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Re: exchange diffs

Postby nobby » May 6th, 2016, 9:40 am

Good news.
Everything on mine was drained and refilled with decent oils over the winter.

Now that we are having summer in the uk I've been running the mutt as a daily toy and it seems to be quieting down nicely.

Perhaps there is hope
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Re: exchange diffs

Postby Bart1015 » May 7th, 2016, 1:52 am

I cut a horse stall mat to fit the rear floor and it helped a lot.
Pray for our Wolf Hunters.
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Re: exchange diffs

Postby buttanic » November 17th, 2017, 9:44 am

Three 45 pound sand bags in the bed made mine a pleasure to drive. It no longer sounds like the rear diff will shortly self destruct and it improves the ride. I bought some military sand bags and they look like they belong there.
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Re: exchange diffs

Postby bazookajoe » November 18th, 2017, 4:30 pm

As an experiment i put new seals in the diffs on my a-1 and re installed the yokes with new sealant and rubber mounted the diffs with heavy rubber 3/8" thick above the diff and a heavy rubber washer above the mounting nut and steel washer so the diffs were sandwiched in. I feel it made quite a difference in reducing the harmonic vibes that previously occurred. I just thought i would try it as an experiment, I have 4 mutts ,three a-2's one a-1 and the only one that kinda howled was the a-1. All quiet now.
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Re: exchange diffs

Postby bazookajoe » November 21st, 2017, 10:27 pm

You should also check to make sure the rear motor mounts have not compressed to the point that the transmission is resting on the crossmember as that will transmit a lot of noise also. Happened to me....changed to new motor and tranny mounts and quieted things quite a bit.
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