rear diff goin? diagnosis?

Howdy all

I have noticed a large noise/sharp pull when I shift into drive (this only seems to happen when I dont have my foot on the brake and shift from P/R to D).
Howdy all

I Had a buddy come over to diagnose. The drive shaft doesnt jump at all, the u joints are tight and the noise is (As close as I can pinpoint) coming from the rear end which was not my first thought (I thought I had a tranny problem)

theres full fluid in both the rear diff and the tranny and the rear diff seems ok

The tranny mount replacement was successfull. However I am still getting that knock/ slap sound when putting it in gear and when on the freeway. In fact it seems that the noise is definitely coming from the rear differential. I am thinking the gears in there have slipped and the clunk/slap noise is generated when shifting into gear / acceleration. Also its loud in the back of the cab when driving, I know from my old chevy van that's indicator the rear gears are goin. I changed the gear oil today, to see if that'd slow the wearing down. I would appreciate any commentary on whether or not y'all think my diagnosis is correct and tips on what to replace, availability of parts etc.

My plan is to price new set of gears--any experience on this???
or to find a rear diff in good shape at this Jeep yard near my house and just do a swap --again any experienced commentary on this dillemma is appreciated

Y'all have a great week!

Y'all are appreciated
kCASH

need some help here gang

know y'all are busy but sure could use some more experienced guidance on this problemo bf/ore I tear into. I ordered my rear diff kit today, gonna price gears from the bone yard unless y'all know where I can get a good set of aftermarket replacements.

Could you provide us with a little more information about your Jeep such as the year, transmission, and differential...
Is the rear differential a D35, Corp 8.25 or D44 ?
When you drained the rear diff..... did you notice any silver specs or small metal chunks in the gear lube ?

Charles

CharlesS said:

Could you provide us with a little more information about your Jeep such as the year, transmission, and differential...
Is the rear differential a D35, Corp 8.25 or D44 ?
When you drained the rear diff..... did you notice any silver specs or small metal chunks in the gear lube ?

Charles

Click to expand...

Charles
91 cherokee 4x4 automatic, diff is a 8.25
yes I noticed a lot of small silver coloration in the lube oil (no chunks) and when I am shifting and driving I notice a sharp slap/clank sound as the gears engage

thanks

by the way

my best guess is that the gears and or the drive shaft are disengaging when at stop or not accelerating, that's why I hear the pop./slap noise not only shifting from Park but also when driving

I've been told by a post on another jeep forum that I may have two piece axles which could be replaced by better one piece axles--any thoughts?

Probably what the other owner was thinking is that you have a AMC 20 rear differential....
That differential was known to have problems with its two piece axles (splined axle which has a hub held on with a torqued nut) and only came from the factory on older CJs and Jeepsters (that I know of)....
Next time you have the cover off of your rear differential.... place chocks under the front tires, jack up the rear differential, place the transmission in neutral and spin each of the tires separately to inspect the spider and sider gears for abnormal wear. There is a chance you might have a worn out spider gear thrust washer....
Does your differential make any noises while driving at slow or highway speed?

Charles

CharlesS said:

Probably what the other owner was thinking is that you have a AMC 20 rear differential....
That differential was known to have problems with its two piece axles (splined axle which has a hub held on with a torqued nut) and only came from the factory on older CJs and Jeepsters (that I know of)....

Click to expand...

It also came in the full-size Jeeps but with a one-piece axle that wasn't nearly as problematic as the two-piece POS in the CJs.

CharlesS said:

Probably what the other owner was thinking is that you have a AMC 20 rear differential....
That differential was known to have problems with its two piece axles (splined axle which has a hub held on with a torqued nut) and only came from the factory on older CJs and Jeepsters (that I know of)....
Next time you have the cover off of your rear differential.... place chocks under the front tires, jack up the rear differential, place the transmission in neutral and spin each of the tires separately to inspect the spider and sider gears for abnormal wear. There is a chance you might have a worn out spider gear thrust washer....
Does your differential make any noises while driving at slow or highway speed?

Charles

Click to expand...

Yep he had an older CJ, and yes the slap/pop noise is loudest when shifting from P to D, however you can hear it when driving also (when you take your foot off the gas-and then re-engage the gas there's that distinct slap/pop sound its not as loud tho'). ALso I hear the diff get louder as I get faster and faster, I know it has to be rebuilt, and I've ordered the full diff bearing kit, however if I have gears worn out this'll only fix part of the problem

what I'd ideally like to do is gut the damn thing and start w/ new stuff, is the dealer the place to for that kind of stuff or is there an aftermarket alternative (e.g. spider and sider gears and thrust washer)

Yucca-Man said:

It also came in the full-size Jeeps but with a one-piece axle that wasn't nearly as problematic as the two-piece POS in the CJs.

Click to expand...

thanks Jim

Since you have a 91 XJ with Corp 8.25 then it is safe to assume that you have 27 spline axles... unless someone swapped in 29 splines when you werent looking (doubt it....).
You can ask several of the local Jeep owers where they go for their differential work... I am sure there is a Off Road shop in your area that does quality work.... Make sure to ask about any problems they have encountered with quality of work, warranty and vehicle delivery time.....
You need to decide how much you are willing to invest to get the differential working properly and what modifications you might want to do since the carrier will be removed while rebuilding the assembly....
You can install gears, locker, axles..... etc.... $$$$$$$$$
IF you need a new carrier then swap in 29 spline axles which will require two 29 spline axles and a new carrier. $$$$$$$$$$$$$$

Just need to decide what your budget is !!!!!

Charles

kcash1 said:

when you take your foot off the gas-and then re-engage the gas there's that distinct slap/pop sound its not as loud tho'). ALso I hear the diff get louder as I get faster and faster, I know it has to be rebuilt, and I've ordered the full diff bearing kit, however if I have gears worn out this'll only fix part of the problem

Click to expand...

I had a slight bump like that for a while (though not when going from park to drive), and it turned out to be suspension play and worn out rear driveshaft u-joints. Assuming your rear d/s is fine, we can eliminate that, I think.

On the noise, I'm hearing/feeling more noise after I pass about 65mph, but I think in my case the rear leaves are going and I'm getting spring wrap that's screwing with my driveline angles, and contributing to the bump I mentioned above.

Food for thought - what kind of miles do you have on this thing, and how do the rear leaves look? My 27-spline 8.25 is still going strong at 208,500 miles, but the silver you report in the diff lube isn't exactly an encouraging sign.

Rob Mayercik said:

I had a slight bump like that for a while (though not when going from park to drive), and it turned out to be suspension play and worn out rear driveshaft u-joints. Assuming your rear d/s is fine, we can eliminate that, I think.

On the noise, I'm hearing/feeling more noise after I pass about 65mph, but I think in my case the rear leaves are going and I'm getting spring wrap that's screwing with my driveline angles, and contributing to the bump I mentioned above.

Food for thought - what kind of miles do you have on this thing, and how do the rear leaves look? My 27-spline 8.25 is still going strong at 208,500 miles, but the silver you report in the diff lube isn't exactly an encouraging sign.

Click to expand...

Rob I've got 210k and she's strong everywhere tranny motor etc, the fuel sys has been completely r/r as well as the cooling sys. Honestly I dont really remember this noise before last month, perhaps I had so many other things to take care of I didnt notice it. The rear leaves look flat, but I replaced the shocks w/some "heavy duty truck shocks" and they dont seem to be doing the Job (the parts stores here no longer carried the ones I wanted to order). I am going to swap the "hdts" out for some load levelers (the shocks w/ the springs around them) b/c the rear end slams hard when off roading or going over big bumps. I definitely am getting some play from the leaf's b/c they're holding more than their share of the rear suspension. We'll see what happens when I put some beefy shocks on her.

I agree the silver is not encouraging and I believe that noise from the rear end is reduced since changing the fluid. I think that I will go ahead and change the Ujoints b/c at 210k its already on my list of Preventative maintenance steps (and its cheap to fix), however the fact that the joints are tight and they dont PING made me think perhaps the prob is the diff. Listening for a PING noise from a worn Ujoint could be relying too heavily on my GM experience, when a GM Ujoint wears you'll hear a very characteristic pinging when shifting b/fore it goes, and this is my 1st jeep.

CharlesS said:

Since you have a 91 XJ with Corp 8.25 then it is safe to assume that you have 27 spline axles... unless someone swapped in 29 splines when you werent looking (doubt it....).
You can ask several of the local Jeep owers where they go for their differential work... I am sure there is a Off Road shop in your area that does quality work.... Make sure to ask about any problems they have encountered with quality of work, warranty and vehicle delivery time.....
You need to decide how much you are willing to invest to get the differential working properly and what modifications you might want to do since the carrier will be removed while rebuilding the assembly....
You can install gears, locker, axles..... etc.... $$$$$$$$$
IF you need a new carrier then swap in 29 spline axles which will require two 29 spline axles and a new carrier. $$$$$$$$$$$$$$

Just need to decide what your budget is !!!!!

Charles

Click to expand...

Well charles I was planning on doing this myself, I've got two vehicles and this is kind of a hobby, but I've been looking through the manual and it does seem to be a bear of a job (*esp pulling the bearings). I've got a slew of jeep shops around to price, but what I'd really like to know is where to buy a new carrier and axles, sounds like from what you've said a 4x4 shop is where I need to go

last nite pulled off the driveshaft replaced my u joints and the jeep sounds much better. she may be all fixed for now, I dont get the slap/pop noise anymore while driving or shifting (although I heard it once after I installed the driveshaft--I'll keep an eye onthat)

thanks for all y'alls help

Also check your upper shock mounts those barpins make alot of noise if the rubber bushing moves or wears out.

big,

ROGER WILCO

I've replaced the rear shocks w/ a pair of load levelers from monroe, that has alleviated the strain on the leaf springs and she's riding much better and quieter. I'm gonna get a pair of the same for the front shocks, event though I just replaced all 4 of them less than 4 mo ago, the ones I put on are just not heavy duty enough to support this ol' girl.