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whine and rumble in overdrive (38-45), disappears at 55-60 on highway

bpatto10

NAXJA Forum User
Location
knoxville, tn
Hello,
I have a 1996 Jeep XJ stock, 6 cyl/4.0 engine, 4WD, AW4 transmission, 231J transfer case and Chrysler 8.25 axle, with 245000 miles.

I get a rumble sound (wa-wa-wa) sound as soon as I hit 38-45 (i.e. overdrive) accompanied by a whining noise. The rumble and whine seem to disappear when I get in the 55-60 range. I really don't feel a vibration that correlates with the whine and rumble, other than the normal vibrations of a 20 year old vehicle.

The local Jeep dealer said it was my differential, rebuilt my rear axle, and the noise did not change at all. I was P.O'ed.

I can make the rumble sound almost completely disappear/reappear by shifting from OD to 3rd and back. The torque convertor was replaced last year.

Other places have told me its the transfer case (91K mile JY case), which I tend to doubt as I recently drained the fluid and it was perfectly clean. No silver or blackness at all. I do this every year anyway. Never saw a hint of silver. I am at a loss as to how a problem in the transfer case would be affected by OD.

Web searches almost immediately led to differential problems for these type of noises. One posting indicated that worn output bearing and/or planetary gears on the transmission could cause whining or rumble noises.

I don't mind replacing the aw4 or transfer case, but I want to make sure I am not overlooking something else or replace the wrong part.

Lots of Grand Cherokee owners complain about a rumble in overdrive at low rpm (such as going up a hill), and everyone says to just live with it.

The combination of whine and rumble is what concerns me.

Other than the noise it drives fine and shifts fine at all speeds and drives fine in 4wd (at low speeds on dirt roads).

Thoughts/suggestions on tests or other areas to check?

Thanks,
Bruce
 
Start with the common issues, and the easy/free stuff. Perform some diagnostics tests and some push/pull/wiggle checks.

How old are the u-joints ? Are the drive shafts still properly balanced ? Is the front slip yoke worn excessively ? What is the condition of the motor mounts and transmission mount ? When was the transmission fluid changed last, and are you using the recommended Dexron-III/Mercon fluids and not using ATF+4 ?

Have you removed the front driveshaft and taken a test drive over the same roads that cause the symptoms ? Now put it back, and remove the rear driveshaft and go for the same test drive in 4x4 Hi. When the driveshaft is removed, check the corresponding pinion for excessive in/out and/or up/down movement.

Most Dealerships know nothing about diagnostics, they are only interested in installing new parts.
 
I will second the removing of driveshafts as above mentioned.


I will also add, pay real close attention the the centering ball in the front driveshaft. That part is often neglected when it should be serviced just the same as the U-joints.
 
Some new information

Thanks for all the replies. I took out the front driveshaft and it made no difference. The rear driveshaft has new u-joints and was balanced about a year ago.

While thinking of new tests to conduct, I changed the spark plugs to RC12LYC as recommended in this thread:

https://www.cherokeeforum.com/f2/idle-miss-mild-vibration-between-750-1000-rpm-250241/

As I expected, it did not make a difference, but the existing plugs had 20K, so it was not a loss. Before calling it a day, I started the engine and put it in neutral just to make sure I had no CEL. When I ran up the rpm, I could still feel the shudder mentioned in the other thread, and surprisingly, the shudder was much stronger as the engine coasted down back to idle. ???

I definitely have something in the engine area or engine itself that needs attention. Could it be possible that this engine problem is also the source of the rumble in the 40-55 range (overdrive) as the torque converter is now directly coupled to the engine?

I have almost convinced myself that the whine is due to improper gear backlash and setup, as I can not think of anything in the engine area that would cause it.

Thanks in advance for any further tests and suggestions.

PS: For the past several weeks, I have been reading threads about whine in the 45-55 mph range under acceleration. It is amazing how many owners of relatively new $30-50K Ford, Chevy, and Dodge RAM trucks are having to have differentials rebuilt or even whole axles replaced under warranty (or having to bite the bullet if outside of warranty) for this very problem.
 
Check the harmonic balancer. See the recent thread on that. At that mileage, I'd change it an ways.
 
Check the harmonic balancer. See the recent thread on that. At that mileage, I'd change it an ways.

Thanks for the harmonic balancer tip. I looked at it after your post and did not see any in/out motion while running, so I thought that it was not the problem.

However, last weekend while crawling around under the jeep to investigate the source of an very small oil leak, which I assumed was the valve cover since it was appearing on the front bell housing cover plate, I noticed the harmonic balancer was beginning to shed rubber, and the area around it was covered in a thin layer of oily dirt.

Sure enough after replacing it and the front seal, the vibrations while revving the engine in idle disappeared, as well as my oil leak.

I still have some vibrations from the engine, as I can see my drivers side door vibrating slightly while in idle, but it is much better.

The whine and rumble are still present at the 40-60 mph speeds, but I am beginning to wonder if this is not engine or engine accessory related as well. I will continue the investigation.

A belated thanks for the suggestion.
 
Okay, so I am narrowing this thing down. No change if I remove the front driveshaft. I bought a infrared thermometer reader from Amazon and tested the differential after an extended 55 mph drive. Temps are in the 130-140 range at the pinion snout, which I think is very good. The front is in the 100-120 range. The rear driveshaft was balanced and new u-joints installed before the tests.

I removed the rear driveshaft and the whine and rumble both disappear completely even at the 45 - 55 mph range. So, in my mind, this eliminates transmission gear whine/wear, and front wheel hub bearings, and only leaves transfer case and differential. Since it does not make the sound in 4wd with the rear driveshaft, I am thinking most of the transfer case must be okay, and the problem is probably in the rear output bearing, since it would have no load with the rear driveshaft removed, and of course load with it installed.

If I were getting higher rear end temps I would have suspected a bad rebuild job, but with the high level of whine and rumble at 50 mph, I don't think I would have such low temps if the differential were the source.

The only concern I have is that I don't see any metal shine when I change the transfer case fluid.

So any thoughts? Anything other possible sources that I should consider?


Two funny side stories:


(1) After reading numerous web articles on similar symptoms, I had totally convinced myself that it was a bad wheel bearing, even though the present ones only have about 15K on them and they passed the tire twist test, the swerve side to side test and the "hand on the coil springs" while turning the tires test. But removing the rear drive shaft and not hearing the whine at the 45 mph point where it always previously started shot that theory down cold.

(2) I stopped at a local garage based on a recommendation from a fellow jeeper I met at Pull-a-Part. He had a lift kit installed by them and gushed over their "jeep guy". So, I stopped by and had their "jeep guy" take it for a short spin. He came back and immediately showed me a 3d infrared temperature scan of my rear axle. It of course showed the pinion area as the hottest area with a bright white color. It looked bad, and then he said "the differential is overheating, it is reading 130 in the pinion area". He immediately starts working me up a quote on a "Jasper axle". I thought "damn, 130C ~ 260 F, that is HOT. No wonder it is whining". I then asked, "130 C right"? (Most infrared devices will read either degrees C or degrees F). This guy, who is in his late 20's at most, says "no, degrees F". I looked at him incredulously, took his quote, and told him "I would think about it".

I didn't have the heart to point out to him that the human body runs about 97-98 F, and water does not boil until 212 F. 130 F is not HOT.

That is why I purchased my own $30 infrared temp sensor from Amazon. That 3d temp scanner he used costs about $500, but it is useless if you don't have a feel for temperature readings.
 
Pulling the rear driveshaft isolated the issue to the rear. If all is fine with the driveshaft joints (SYE?), then it is rear axle related. Whine is almost always gear related. Pull the diff cover and post up pix of the gears.

Ideally you would flush the oil off the gears with carb cleaner and then do a pattern check.

From my experience of 25 years of dealing with axles, I would list the following in order of probability.

1) poorly set up gears
2) bad pinion bearings/wrong pinion nut torque (too low or backing off)

I didn't see where you said what axle type....

3) bad wheel bearing
 
It looked bad, and then he said "the differential is overheating, it is reading 130 in the pinion area". He immediately starts working me up a quote on a "Jasper axle". I thought "damn, 130C ~ 260 F, that is HOT. No wonder it is whining". I then asked, "130 C right"? (Most infrared devices will read either degrees C or degrees F). This guy, who is in his late 20's at most, says "no, degrees F". I looked at him incredulously, took his quote, and told him "I would think about it".


130*F is perfectly normal if he drove it at speed. Even up to 190*F is normal if you've been hauling a trailer uphill at speed. The temperature is going to go up, simply because you're doing work to heavy gear oil. Sounds like they have a nice scam going, convincing people they have a bad rear axle.
 
Thanks to all that posted to this thread. I wanted to give an update, as I always hate it when someone posts a problem and never gives a final resolution.

Tom was right. It was the pinion bearings. I went back to the shop that did the ring and pinion install, and I convinced them to do a test drive with and without the rear drive shaft installed. The total lack of noise without the rear drive shaft convinced them that the problem was indeed the rear differential, and not the transfer case.

However, they were concerned because of the 2" lift caused by my new heavy duty springs, as you could feel a definite vibration upon takeoff especially at the 35-45 mph range. They wanted to do a transfer case rebuild (150K miles) with a SYE. I was hesitant, but I realized that if I did not do it, any future differential problems would be blamed on this vibration problem.

So they redid the setup with new pinion bearings, along with the rebuild and SYE. The whine at 45-55 is finally GONE, but I still have a little at 35-45. They noted that as well, and recommended that I drive it for 500-1000 miles and see if it goes away as the new setup wears in a little. It does indeed seem to be getting better each week.

I was very hesitant on the SYE, as I don't off-road other than forest service roads during hunting season. The re-builder felt that all XJ's should have a SYE, as he viewed this as it's biggest design flaw, and he felt that it was even necessary for a street only vehicle. I thought yeah, yeah , you just want the work. Boy was I wrong! Driving home I was shocked at how much smoother the whole jeep felt during acceleration. After about a week of driving with the SYE, I realized I should have done this years ago, even though I don't off-road.

I am happy with how everything turned out, even though I did have to spend some extra money on it.

Again, thanks to all.
 
I was very hesitant on the SYE, as I don't off-road other than forest service roads during hunting season. The re-builder felt that all XJ's should have a SYE, as he viewed this as it's biggest design flaw, and he felt that it was even necessary for a street only vehicle. I thought yeah, yeah , you just want the work. Boy was I wrong! Driving home I was shocked at how much smoother the whole jeep felt during acceleration. After about a week of driving with the SYE, I realized I should have done this years ago, even though I don't off-road.

The 97-01 models had a lot of driveline vibe issues with the rear driveshaft because of the change to the transfer case's rear output (they moved the slip yoke completely outside the case housing, so more unsupported weight on the output bearings, unlike the earlier models where the rear shaft's slip yoke goes right into the rear of the case). My '92 needed a 1 inch tcase drop when I put the original 2 inch lift on it years ago, though it may have simply been wear patterns in the ujoints, but I've gone up another couple inches over the years without any further vibe issues.

The 1996 model year, while it looks like the older models, was a transition year - they usually have a seemingly random mix of older and newer parts styles. Which vehicle has which combination varies, but in general the later 96s are more like the 97+ and the earlier ones are more like the 84-95s. It could be that your particular 96 has a 97+-style tcase.
 
Rob,

It is indeed a late model 1996 with the slip yoke completely outside the transfer case. In fact, I have encountered some 1997 parts on my vehicle. I had a Jeep service manager tell me that during the 1996 switchover, if they ran out of 96 parts on the assembly line, they would grab parts out of the 1997 bins to finish the vehicle. I have encountered this mainly in the electrical system.

I have learned the hard way to physically look at the exact vehicle part before ordering a replacement. :D
 
Yep, the 96s are truly "Just Empty Every Parts bin" made manifest..
 
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