I just purchased my first Gran Cherokee. Its a 96, with a 4.0 automatic, with AWD, no way of taking it out of 4WD. I didn't know they made them that way.
Very clean, and runs perfect, I really like this truck! 155K on the clock.
When I went to see it, the guy was very helpful, and told me to drive it though, he wanted me to hear the noise.
When he bought it a few years ago, "he only use it during the winters", he said the front drive shaft was not on it.
The previous owner had removed it. He put a drive shaft on from a junkyard, and got the bolts and everything.
He did replace the front hubs when he got it, since they were making noise. Thats when he noticed the other noise, when he got the hubs quieted down. Its not loud, but hear it with the radio off.
When you get up to about 35-40 mph, that when the humming/whining starts, while in motion, you can let of the gas, and it stops making the noise right away.
But soon as you hit the gas the noise is there. It doesn't get louder with the speed. Stays the same.
He said his buddy told him it was pinion or something on the front, but wasn't sure.
Any ideas, on how I can check this, or is there any advice on this? Like a common problem that happens to these? Otherwise the truck is awesome!!
No rust, and very clean, and even the interior is perfect!

 

If it has the D30 in front, you may want to take it apart to check the carrier bearings. I had the same problem with my 99 Jeep Cherokee and I replaced the carrier bearings, races, and the axle seals. After I refilled it with fluid, I took it for a drive and it was fixed.

 

It sounds like the 249 Quadratrac transfer case and they don't like running around with the front shaft removed. There is a viscous coupling in the transfer case that absorbs the slippage between the axles and overheats and stops working after a while. You can check if it's working by doing some circles and checking if the front tires hop or grind. The viscous coupling is an expensive part and is a PITA to replace. So much so that most people go for a swap to the 242 or 231 t/case.

Check out this link for info on the case and swap options; http://jeepforum.com/forum/f13/trans...-np242-685644/

 

I may have to take that too a garage. I never messed around with the diff. I can see the seal looks egged slightly and is leaking, but I topped it off. I think the pinion bearing might have worn out after looking at it this morning.

 

It does have a slight binding on hard turns. I looked at a you tube clip on the viscous. Looks like its not very much fun to do, unless you remove the transfer case. I dont know how hard they are to remove. Just from the loks of my front pinion seal it appears it is egg shaped slightly and probably the pinion bearing on the front axle might be worn then? I am wondering if this viscous caused this.

 

Grab the pinion yoke and try moving it up and down violently. Any movement will be bad pinion bearings.

 

I am really getting irritated. This guy has had my Jeep for almost two weeks. I keep calling him, and he says he is just so busy.
He did test drive it last week, and said he could hear the grinding noise start at 40mph, then letting off the gas he agreed, that it stopped when he did that, and started again when hit the throttle. He says he agreed with me also that it seemed like the front pinion bearing.
I called him today, and told him it has been two weeks, I need my truck back.
He said he is so busy, and will try to put it on the rack today and run it, and check to see what it is now. He didn't want to take it apart yet, now he thinks it may be something else. I asked him if it was the tranny. He said, he believed it was in the front end. I wished he would just fix it, or see what it is. I am burning out!!

 

Rebuilding a differential is not for the faint hearted and he probably doesn't want to get involved. Get it back and take it to a good driveline shop, one that services big trucks.

 

X2 on that advice.

Max

 

Ez way to test if it is front take out rear drive shaft put front on Jack stands at least four . 2 on axle 2 on frame and put on emergency brake put it in gear and listen for the noise if it is front diff ull hear it with door open and they are ex fix I could talk u step by step through the rebuild

 

Oh crap!!! I really need advice! I left it a little longer with my mechanic.
He finally took it apart today. He just called me.
He said the bearings, and everything in the front axle are perfect....
I am lost!
He even said he agreed with me, l that the sound seemed to be coming from that front axle. At 40mph, it starts, if you let off the throttle, the noise stops, till you hit the throttle again. Like when the pressure is put on under load.
He is going to put it together tomorrow, and leave the drive shaft off, and see if the noise is gone.
Wonder if it could be in my transfer case? I know my VC needs replaced due to the buckling on bends, but is my transfer case just wore out, and do they make those noises??
I am confused with this grinding/humming noise.
It sure seemed to be coming from that front end. He even agreed. I am so lost, I need it on the road. ugh!!!!

 

Bump.....Sorry to be a pain guys. Anyone have any ideas about my above post?
I should have the ZJ back tomorrow.
I know I will need a VC in the transfer case since it does that buckling thing when turning.
But since he said the pinion bearings are not bad and looked good, I don't know what to do! I guess he could tell by the races looking like new, and the bearings looked great.
I know that sound was coming from the front end when under pressure. Unless the sound is traveling along and making it sound that way.
I am so confused.

 

If you're asking for my opinion, if he had the pinion out to see the bearings, chances are he didn't get the bearing preload right putting it back together. Now you REALLY need professional help!

 

He's actually really good at doing that stuff, thats why I left it there. He is really backed up on work, he does all of the police cars around here...etc.
I am calling him today, and see if its back together.
Funny you brought that up. I am wondering when he puts it back together, if the noise will be gone. Even though he is only going to replace the crush sleeve, and seal. He said the bearings looked new. I am now wondering if the last guy had it apart, and didn't do it right. He bought it with no driveshaft on it. Makes me wonder if he was playing in there.
If it isn't that, I am thinking the only other thing is the transfer case, a bearing or something? I am sorry, I know I am being a pain. I just never ran into this issue with anything.
I have to change my VC when I get it back. SO hopefully there is a way of me checking the transfer case too, to see if thats the issue.

 

The jeep only does it when you are turning?? If this is the case, I would be looking at the shafts in the front axle because if those boots are split and leaked out the grease then I would be willing to bet that the shaft joints are bad and they need to be rebuilt or replaced. I have already done one on my WJ and when this snow goes away I will be pulling out the other shaft to replace the boot and rebuild the joint.