Rear differential

[bollio]

The rear differential on my 98 Jeep Cherokee is making a whining noise that goes away above 50 mph. I took off the cover and changed the fluid but it still makes a noise. When jacked up and in drive one wheel spins really fasst while the other is barely turning. Is this normal?. Any suggestions ?

[swanny]

Originally Posted by bollio

The rear differential on my 98 Jeep Cherokee is making a whining noise that goes away above 50 mph. I took off the cover and changed the fluid but it still makes a noise. When jacked up and in drive one wheel spins really fasst while the other is barely turning. Is this normal?. Any suggestions ?

When one wheel spins and the other stays still or barely turns (you can actually stop the slower one by hand but don't try it) while you have them both in the air implies that you have what is referred to as an open or non-locking differential. The term differential implies that both wheels are allowed to spin at different speeds if they need to. For instance when you go around a corner the outer tire covers more distance than the inside tire in the same amount of time therefore it must spin faster. If this didn't occur and they were both forced to spin the same speed the inside tire would spin out and lose traction even on the pavement because it would be spinning as fast as the outside tire but covering a shorter distance, this would lead to tires wearing out much faster than needed. Also losing traction with the ground is dangerous. There are lockers available that do lock both wheels together for extra traction but they should be reserved for off-road use. You may have heard of limited slip as well. In a nutshell it is a middle ground between a locker and an open diff. It alows for a limited number of unequal tire revolutions before joining the two axles together for added traction. They are great for snow and ice country because they unlock and lock automatically depending on the traction requirements. So any way to answer your question, yes what you observed was normal for the type of differential you have. Now on to your noise. I have a 98 cherokee with the Dana 35 rear axle. When I first got it (used with 100K miles) it had a whining slightly noticeable noise coming from the rear much like yours I would imagine. It did seem to go away the faster I drove but that may be a result of other road and wind noise drowning it out. Whatever the noise was I didn't worry much about it until the day I got a flat tire on the rear. My spare was smaller than the tires on the ground so on the way home (down the highway at 65mph) that whining noise in the rear probably increased to 100 times louder, it sounded like I had a jet engine in the back. I knew I needed to inspect my rear diff now! Upon removing the rear cover I noted that the spider gears (these are the 4 smaller gears clustered in the center of the housing responsible for the differentiating action of the differential that I mentioned above) were severely pitted on the teeth where they contact each other. By driving with different sized tires the axles spun at different speeds. So even though I was traveling in a straight line these gears were forced to spin against each other at a very high rate of speed (65 mph). Normally they only turn against each other while turning and that is usually slower than 20 mph. There really wasn't any metal shavings or chunks to speak of only a thick pasty coating of heavy oil in the bottom of the case and the inside of the cover. The gears were pitted not because I had driven with an odd size tire but because at some time in the past they became so hot that they became molten and shed off some of their metal. I knew this was bad so I disassembled the rest of the differential to inspect the carrier bearings and pinion bearings. They had also gotten hot and recieves some noticable pitting (bearings and gear teeth should look bright shiny and smooth as glass). Luckily the ring gear and pinion gear looked fine so all I need are four bearings and four spider gears, about $150-$200 worth of parts. So if I were you I would pull the cover, get a really bright light and inspect the actual contact face of all the teath of all your gears and then if they are fine remove the carrier and inspect your bearings. You'll have to pull the axles to do this so take a good look at the axle bearings also which are located inside the axle tube just behind your brakes. I would be willing to bet that your problem lies in one of those areas. Good Luck

[IdahoJeeper]

Whew!

[vamc]

Sounds good over here. wow

[bollio]

Thanks for such a detailed reply. After having removed the cover and inspecting it appears to me that the only thing worth noting is that the teeth on the large ring are razor sharp. Is this an indication that they are worn. Also after removing the axle shaft the wheel bearings rollers in the wheel bearings seem to have a lot of movement. What are the signs of a worn bearing.
I want to order new parts but I am unsure if I have a Chrysler 8.25 or a Dana 35 axle. How do you distinguish between the two ?

[hiduke89]

Originally Posted by bollio

I want to order new parts but I am unsure if I have a Chrysler 8.25 or a Dana 35 axle. How do you distinguish between the two ?

What I did was just looked at "jeep essentials". If you don't kno what that is, its a catalog for only jeep parts. They usually have a blow up of the two axles and once you look at them and your axle it will be pretty easy to tell.

[hiduke89]

Also not sure if this helps but I have an 89 cherokee and it has the dana 35 rear axle.

[hiduke89]

Sorry about all the replys but i came across this whille looking for a part for my XJ thought it may help.

http://www.jeep4x4center.com/cheroke...ationChart.htm