Jeep driveline noise?

[PToombs]

Hey guys, I have a '96 Grand Cherokee Laredo, limited slip rear, full time 4x4. The darn thing has a whine in the rear end that's driving my wife nuts. (short drive ) It sounds like a bearing noise, and gets real loud after 50-55 mph. I drained the rear axle oil, and it was like tar, checked for play, none in the pinion, carrier, or axles. I did see seepage at the right backing plate, so I checked close there, no play. I refilled the diff, and overfilled about 1/2 way up the hole. No difference. I jacked it up and ran it in the air, no noise. It looked like the right rear wheel wobbled a little. I suspect the shaft is bent a little bit. I checked the TC, it was low, about 1. 5-2", so I drained it and refilled, also over filled about 1/2 a quart. Slight play on the rear output shaft. Still the same, noisy. I had my buddy drive, and I got in the back and listened, sounded like it was coming from the right rear again. I pulled it apart and replaced the wheel bearing and the seal. The inside of the race looked real cloudy and pitted (rollers came out on removal). The shaft didn't look too bad, I polished it with some emery and stuffed it back in. Filled up the same amount, and drove it. Still whines, and it almost sounds like it's a little louder. I'm real frustrated with this thing,and any bright ideas would be very welcome about now.

Sorry for the novel, but I wanted to get all the facts out.

 

[BHanna]

How's the wear on that right rear tire? If it's wobbling, you'd expect it to be uneven (probably cupped). Maybe try rotating the tires and see if the noise moves? If not, you can rule out the tires. If the noise moves, it could just be the tires but you probably want to try a new axleshaft if the wheel's wobbling. Even if the shaft is straight, the wheel mounting flange could be tweaked out of perpendicular.

 

[JLEONARD]

My son told me many years ago that the pinion bearing pre-load goes out on those. You may need to reset the preload, or install a new bearing.

 

[PToombs]

BH, currently there are studded snows on it. Noisy buggers, but the wife doesn't get stuck. I put the summer tires back on it and the noise stayed the same. I thought even if it is the axle, the noise should change with the new bearing. If it did, I'd put in an axle shaft in a minute, it didn't, so I'm still looking.

Jay, I shook the pinion shaft, no play in it. No play anywheres. If the pre-load goes will it get play?

Appreciate the help guys, keep 'em coming!

 

[BHanna]

You may not have play with the wrong pinion preload (at least not enough to notice wiggling it with your hand). You measure it with a dial-type in/lb torque wrench and see how much force it takes to rotate the pinion. Even if it's a little bit out of spec it can make a horrible whine but it usually varies when you step on the gas or let it off. It would also come from the center of the car.

 

[UAV]

At minimum the carrier needs to be removed to get close to an accurate pinion bearing preload reading.



Does your ZJ have the aluminum housing Dana 44? It has problems with spinning carrier bearings due to deflection in the softer housing. If a carrier bearing has spun you may have insufficient preload on the carrier and it can move around under load, you wouldn't be able to duplicate it trying to move it by hand. It may be a bearing noise or due to the backlash having opened up causing the gear set to become noisy.



Check the backlash, this is very easy to do. If you don't have a dial indicator you can pick one up at Harbor Freight for $30. If you find the B/L is much greater than . 010" (usually B/L spec is . 006"-. 010") you may want to have an expert look at it before it experiences a catastrophic failure.

 

[PToombs]

It has the steel housing, pretty sure it's the Dana 35 because it has the 4. 0 inline 6. At least that's the bearing I got for it.

The noise changes a little bit when I hit it or let off. Not enough to make me think pinion slop though. It sure sounds like it's the right rear. I'll have my buddy ride in back and get his opinion. He drove last time.

I just want the noise to go away so I can sell the darn thing. I'm not against putting a $100 or so into it so I don't lose a bigger chunk of change.

 

[PToombs]

Well, I pulled the drive shaft out of it today and went for a ride. It still makes the noise, but it was reduced to 1/4 to 1/3rd of what it was. Definitely in the rearend someplace. I know it's not as good as a dial indicator, but I grabbed the yoke and could turn it about 1/8" before it stopped. Too much play? When the wife doesn't need it later in the week I'll pull the cover and look at it again closer.

 

[PToombs]

Ok, update! I rotated the rear wheel next to a stationary object, and there is no wobble, so the axle is straight. I pulled the carrier and put in new bearings and shims, about . 008 backlash on the pinion, and some preload on the carrier bearings. Not positive on how much, about . 005 I think. The left axle bearing looks good. I took it for a drive, and it as loud or louder than before. It definitely changes when you hit or let off it. I tightened the pinion nut just enough to turn it, thinking that would change the sound, nope!

I give up, when I find the wife a new car, it goes, noisy or not!