rear end roar and vibration
 

Hi guys, I just got a 98 Grand Cherokee, 165K miles, 4WD. The rear end is sounding like a whine/roar when driving above 35mph and increases when I let off the accelerator. Also I start getting a vibration when I reach 70 mph. I removed the diff cover, cleaned it out good, and refilled it. I didnt see anything wrong other than the old fluid was real thin and dirty. Yes both rear tires are the same size. Also replaced the shocks and brakes.
Any ideas?

I'm wanting to drive this out of state this weekend, should I?

Thanks in advance!
Tom

I've got a similar issue with my ZJ. For me, it's my pinion bearing and possibly the bearings inside the diff itself. When I take my foot off the gas the rear end sounds like a siren from a fire truck winding down. Pull your e brake, put it neutral, and get underneath and grab the drive shaft where it meets the rear diff and try to see if it moves. If it slops around, that could be your problem. I'm just keeping my driving to local stuff...just in case the rear end decides to go pop. Just my 2 cents.

Well I just took it to PepBoys and had them check it out. They only charged me $20 and told me it was my drivers side wheel bearing. Not a bad price at all for them to tell me which one to change. Now lets just hope their right! To be continued...

Well I changed the drivers side wheel bearing and its still making noise and vibrating. Pepboys was wrong.
While under there, I noticed a nice dent on the the drive shaft, looks like it hit a big rock. I wonder if this could be causing my vibrations.

Had the same problem.. Theres a bearing inside your rear end. The universal joint and drive shaft ride on it. I cant remember exactly what its called. Seems like its a carrier bearing or something like that. Hope that helps.

i would say the vibration is the drive shaft, mine let go a few weeks ago on a old chrysler c body i own, it had had a vib for about a month that i thought was a wheel bearing as well.
get it checked or changed before it does more driveline damage.

The '97 V8 ZJ I had was doing the same thing when I bought it. I took it in to a repair shop to be checked out. It was bad pinion bearings, bad/worn ring & pinion gears, bad carrier bearings, and bad wheel bearings. After the rebuild it was as quiet as a new unit. The cost was $1,400.

Mine is doing same thing, I just rebuilt the transmission, can't afford to rebuild the rear, ugh...

The imbalance because of the dent caused overstress on the pinion bearings which caused them to wear out. I wouldn't drive it on the highway too far. My '97 ZJ had the same problem with the pinion bearings. I decided to go see my brother who was about an hour and a half away on the highway. An hour into my trip, the rear end BLEW! And I mean crunch&munch. I slipped it into 4WD and nursed it on surface streets the rest of the way, leaving a trail of fluid. When we got there, the pinion wasn't even touching the ring gear and the bearings were in pieces. We took the rear driveshaft out (it mounted on a flange rather than a slip yoke) and I drove it home at 40 mph on surface streets with the front diff doing all the work. It had the 242 t/case so I wasn't worried about toasting the viscous clutch. I got it rebuilt for free (another story) but it wasn't done right and it whined until I got rid of it.

You can take your chances with a used axle or get it repaired PROPERLY by a qualified mechanic. It takes attention to detail to set the pinion preload and gear lash properly and someone who's done it before. The D35 rear axle (if it's a 4.0) is one of the weak links in this model, others being the trans and the 249 t/case.

A little info on the differential. The pinion gear is the small one driven by the driveshaft. It is mounted on 2 bearings and preloaded by a crush sleeve in between. This keeps the gear from moving back and forth away from the ring gear when you add or remove power. The ring gear is mounted on the carrier assembly and is supported on 2 side bearings called the carrier bearings. In my opinion, the D35 is too light to be used in a vehicle used off-road. It is tiny compared to the diff in my 3/4 ton Chevy truck.

I've run into what I thought was wheel bearing noise ended up being the carrier bearings gone bad on two of my Grand Cherokees now ( both have high mileage) if you have access to a hoist or really good jack stands get under the car with a stethoscope while the car is in gear and the rear axel is is rolling and listen with the stethoscope to where the wheel bearings are and also listen to where the axle tubes run into the diff that's about where the carrier bearings are also listen to where the drive shaft runs into the diff that's about where the pinion bearings are you'll hear where the noise is coming from if you don't have a stethoscope you can use a screwdriver flat tips work best press the flat tip against the axle or diff and press your ear against the end of the handle I know it sounds a little hill billy but it works hope this helps

low roar in rear, Grand Cherokee 2002
 

My 2002 Grand Cherokee has developed a low roar while driving. It is a low roar, but still a noise that should not be there.


I would appreciate any advise.


Mike in Virginia Beach


I changed the rear brake pads and now both rear brakes are running hot.


I noted that the new brake pads from auto zone came with now brake pad guides. And, there were none on my jeeps when I took it apart. So, put new brake pads on with out the guide clips. Will that cause the brakes to run hot.


I would suspect a sticking caliper. But, seem that both would stick at the same time.


I am totally confused.


I will appreciate any help.


Michael in Virginia Beach

Same thing, Mikey! Worn bearings and gears, not terrible at the moment, but something to watch. My 2000 has a low hum at 65 or above that changes with power level. I've got 212K miles on her now so it's not unexpected. I have the 242 t/case so I run in 2wd most of the time. 4wd is quiet as a mouse, but I don't run above 65 in that mode. I thought the hum was the tires until I realized it was quite in 4wd or at least not as loud. There is a tiny bit of backlash in the pinion, but the gears show full face wear with no scoring. I've been running 75W-140 Synthetic gear lube for about 100K miles.

The funny thing is I've been keeping a close watch on the driveshaft universal joints because as far as I know they are original, and with 212K on them, I expect them to go soon. They still don't show any signs of being dry or looseness. That's on BOTH shafts.

Welcome back! I haven't heard from you in a while.

Thanks for the feedback
 

Hey Dave,

Thank you and all the other members who take their time out to answer my call for help. Experience is a great thing. This low roar just started and my wife heard it first.

Jeez, I hope I don't have to work on the axel and differential. Don't have the tools and lift.

I changed the oil in the differential yesterday. On youtube,, it looks easy to pull the cover on the differential, but it did not say that the gas tank is in the way. lol

My Jeep has 105,000 miles.

I pulled and pushed on the drive shaft and it seems firm with no play.

Also, changed the brake shoes on rear. Noted that there was slight oil seeping out of the caliper on one side and the dust boot was split. So, am making plans to rebuild the calipers. I have done that before successfully.

I am retired and have a limited budget, so have no choice but to do the work myself at age 80. or park the car. lol

Anyway, just want to thank you and other members for answering my plea for help.

Best regards,

Michael Ange, Virginia Beach, Virginia

Hey Dave,


I am stressed big time now. I replaced rear brake pads correctly, I though. But now they are both sides running hot.


I drove the Jeep down the street and put it in neutral and it started slowing down like I was applying the breaks.


Strange thing, both rear brakes are running hot.


Question: I noted that there were no break pad guides on the brakes caliper body, and none came with the new brakes from Auto Zone.


Would that be the cause.


I could see a sticking caliper. But, seems not both calipers would stick at the same time.


Did I get the wrong brake pads?


It is 11:00 PM here in Virginia Beach, and I will pull the rear tires tomorrow morning.


But, total confused.


If you can help me, appreciate it.


My email address is [michaelangesr@verizon.net]


Thanks,


Mike in Virginia Beach.

I would check the brake line pressure after driving crack one of the rear caliper lines and see if the lines are under pressure. if so the flex line that goes from the body to the diff may have an internal failure where a flap is letting pressure by when braking but acts like a 1 way valve so the fluid can't travel back to the master.

MAX