13667

I have recently become the proud owner of a 2000 Cherokee Sport, 4.0, automatic, 4 door, 4 wheel drive with 147,000 miles. The rear differential is a Chrysler 8.25 rear and it does not have anti lock brakes. It seems to run very well but has a noise that I would like to pinpoint to determine if is of concern or not.

The noise is a whine and it comes from the back of the Jeep. I have no children so it’s not kids in the back seat. The whine occurs only when I am pressing on the accelerator, when I let off of the accelerator the whine stops. The whine starts at around 42 miles per hour and gets louder up to about 50 miles per hour. After 50 or 52 miles per hour the whine essentially goes away. At any time between 42 and 52 mile per hour if I let off of the accelerator pedal the whine stops immediately. I have read in the form that the pinion bearing can make noise when the unit is accelerating and then they stop making noise when the drive train is coasting, but I am not sure how to narrow it down to the exact cause. I’ve not done any differential work before so I hate to tear into it in the garage and find the task is beyond me.

Any ideas what the whining sound could be? If you suspect it is a bearing, can you tell me how to check without complete disassembly? I could take it to a gear shop, but not sure I have the funds right now to address it. It needs a set of tires and I hate to buy a set of tires and then find I need to dump a pile of money into the differential too.

Thanks in advance. I found this forum when I was trying to determine why the passenger door window switches would not work and realized how much information is here. This is a great place! It seems to run very well but has a noise that I would like to pinpoint to determine if it should be of concern or not.

93SVT

If your rear end is anything like mine it has a lot of slop in the spider gears I have a 97 XJ with 160k. The rear end growled ever since I bought the jeep last fall, I thought "no big deal, junkyard rear axle, $100.) 10k later I am still running the same rear axle, I pulled the cover and refilled the axle with 50% gear oil and 50% lucas heavy duty oil stabilizer. It's a super thick oil that can be added to anything, your engine, t-case and axles. The heavy oil will quiet the noise and extend the life of the rear end. This is the cheapest way to go as you should change your diff. fluid at that mileage anyways. You will have around $25.00 into a gasket and oil. You can pretty well check where the noise is coming from yourself. With the jeep in park, elevate the rear axle so that the tires are about an inch off the ground, than put a long prybar ( a rockbar works best) under the tire and see if you have any play up and down. If the wheel has play up anddown The noise could be coming from a worn outer axle bearing (easy $30 fix) If no play in ether of your outer axle bearings then I would pull the cover off the back of the pumpkin. With the rear end elevated and on JACKSTANDS, lay under the back and , with the jeep in park have a buddy turn the rear wheels back and forth, then you can see exactly how much slop is in your spider gears. If your outer axle bearings are tight and there appears to be some slop in the spider gears, then I would refill with a 50/50 mix of lucas and gear oil. This combo greatly reduced the howling noise that was coming from the back of the jeep.

13667

Thanks SVT. I changed the gear oil last weekend using a new gasket but did not think to put the Lucas in. I'll check the wheel bearings like you suggest and I can easily pull the cover and save half of the lube so that I can check the slop between the ring and pinion and toss some Lucas in. I actually looked at Lucas at the auto parts today thinking if I needed something to quiet it down this might work.

KY_Bob

You can get a $5.00 bulb pump that can pump the fluid out of the differential. Autozone has them. That would be a lot easier and since you recently changed it there is no need for a complete dump. The FSM does say to not overfill as it can cause foaming and loss of lubrication action.