Could AW4 solenoids/transfer case/differential be causing my rumble noise?

1996 Jeep Cherokee, AW4, 4WD, Chrysler 8.25 differential, 3.55, 237K miles, Jasper engine with 45K, recent rebuilt front end. recent alignment, recent drive shaft balance with new rear u-joint. New torque converter and transmission oil pump about 3 months ago.

For the past year I have been having a low frequency rumble sound (or whump whump sound) that seems to be coming from the rear and appears in the range of 45-55 and goes away after about 60 mph. It peaks at 50 mph and seems to be reproducible. I also get a slight steering wheel vibration (and dash and rear view mirror, but this could be unrelated).

From the intensity of the sound you would think something major was vibrating, but the vibration intensity isn't as bad as the sound.

This question was posted earlier in this thread:

https://www.naxja.org/forum/showthread.php?t=1140821

I followed all the suggestions (thanks to everyone) and replaced the u-joints with no change in sound. However, I have a new piece of evidence. Every so often (as in very very infrequent), I will sense a feeling that something has engaged or "grabbed", as my rpm's will jump several hundred rpm as if I had downshifted in 3rd gear, and the rumble sound will disappear (or at least is so muffled that I can no longer hear it). If I downshift from OD into 3rd, the rpm's stay the same, as well as if I shift back into OD.

When this happens, if I pull over, turn off the engine and restart, everything runs fine just like before, except now the rumble has returned.

I had the differential rebuilt per the advice of the local Jeep dealer, and the sound did not change. They now admit they don't know the source of the sound. Afterwards, I have had several other places test drive it and the first thing they all say is "bad differential". When I tell them it was just rebuilt, they all say it sounds to them like a bad differential. I had one mechanic tell me that he has seen this occur when the pre-load has been lost on a differential, including the specific occurrence at 45-55. Another one said it might be the 231j rear output shaft bearing.

The rumble is definitely associated with the drive train, as it goes away as soon as I take my foot off the accelerator.

So some possible candidates:

(1) The rumbling is due to transmission drive solenoid chatter, and the 3rd/OD symptoms are due to it sticking.


(2) They really did screw up the differential rebuild. Hence, my question in this thread:

https://www.naxja.org/forum/showthread.php?t=1149560

(3) The rumble is from the transfer case (despite a new output shaft bearing 2 years ago). However, could this explain the 3rd/OD intermittent symptoms?

I will add one other possible pertinent fact. After the rebuild, I went back to the dealer and test drove it with the service manager sitting in the passenger seat. He is a fairly big guy,
and I could not for the life of me get the sound to occur on the test drive in that speed range. This also happened once again on a test drive in which I was sitting in the passenger seat. Just could not duplicate the rumble. Of course with just me in the vehicle on the way home it came back again.

Maybe I am chasing more than one gremlin, and I will just have to "drive it until something fails". I hate hearing that statement. :firedevil

I don't think it's the transfer case or solenoids. It sounds like differentials but as you said, you just had them rebuilt.

I would check the mechanical fan clutch for play and wobble (seriously, DrMoab had a fan clutch so bad he thought it was driveshaft or diff issues a few years ago IIRC...) and possibly the driveshaft ujoints. I'm not 100% on either of those obviously but both are easy and fast to check.

is it lifted? i had a 3" lift on mine and the angles caused the transfer case side of things to not sound healthy.
I currently have a slight vibration issue and faint noise. but i think its internal to my transfer case.

Vibes that come on at those speeds are commonly related to driveshaft issues. If you have replaced the u-joints, including the centering ball on a dual cardan, then you might want to pull the rear driveshaft and drive in front wheel drive only and see if the vibes are still present.

If they aren't, take the shaft and have it checked for balance.

I would look at the slip-yoke/spline. What style t-case do you have((96 is a "tweener" year).

RCP Phx said:

I would look at the slip-yoke/spline. What style t-case do you have((96 is a "tweener" year).

Click to expand...

I have an NP231J with the 27 spline shaft. The driveshaft was balanced about 6 months ago.

You are right about the tweener. It is a late model 1996 and it has both 96 and 97 parts on it. I have to be careful about parts, especially from chain stores.

You know I had not considered the slip yoke begin worn enough to cause the rumble. With 237K miles, I guess it could be starting to wear. Every once in a while I will feel something "grab" or "engage" and the rumble will disappear for a short time. I wonder if this is the slip joint "grabbing" momentarily.

A new slip yoke is not that expensive. It is worth a try.

Thanks for the suggestion.

I know you have a 231, the question was do have a "to 96" or a "97-01" t-case. The late model case has a "exposed" slip-yoke vs the earlier "wet/oiled" slip-yoke.

Yes, I have the sealed type transfer case, in which the slip yoke is external and does not rely on the transfer case transmission fluid for lubrication.

I would definitely lube it up and try it. The 97-01 cases are notorious for vibes regardless of lift!

It's 95 down vs 96 up. Model year, not build date. I've worked on dozens of 96s from all over the build date spectrum and every one has had a grease booted slip yoke.