lfhoward

Here's a mystery: I get a clunk from my rear diff when switching from forward to reverse or vice versa. Occasionally it also clunks when I decelerate quickly using the brakes. I am pretty sure it's not a u joint in my driveshaft because when I jacked the rear up, then turned a wheel, there was a hesitation and a clunk before the other rear wheel turned in the opposite direction. And there didn't seem to be any play in the driveshaft when I tried to turn it manually. It seems like something is loose inside the diff. But there are no bad noises while driving. What do you all think it could be? I've searched and haven't come across a situation just like mine (usually it's a driveshaft u joint). Some info about my XJ: I am pretty sure its the Chrysler diff (flat bottom) and I have an AW4 transmission with the command trac transfer case (no full time 4 wheel drive). It's a stock 2000 Sport with 112,500 miles. Do I need to change the diff fluid or are we talking about replacing something mechanical in there? Thanks in advance for your thoughts!

lfhoward

I should also mention that my u bolts connecting the axle to the leaf springs seem solid.

djb383

I think the clunk is a Chrysler thing. Never hurts to change the gear oil but probably won't change the clunk.

peep

If you are sure the noise is internal to the diff there is no harm in having a look. Have at least 1400 ml plus of 75-90W diff oil on hand. Have some good gasket sealant ("the right stuff" brand is great) on hand. Have a pan to catch the old fluid and a roll of towels. Pull your rear cover and clean up the sealing surface. Have a good look inside for any visual problems and look into the old fluid. You can rock the gears back and forth, watch your fingers please. Seal it up, bolt tight but not crazy tight, 35 ft lb is lots, use antiseize on the fasteners, add the fluid till it spills out the fill hole. Google will lead you to lots of video on the process (I am too computer illiterate to know how to post a link). The new fluid won't hurt your jeep. Post us what you see inside.

sandaddik2

sounds like you have a little much back lash in the ring and pinion, it most likely isnt going to break tomorrow but itll shorten the life of your gears

lfhoward

I thought I would post an update for anyone who ends up searching this topic. Recently I replaced my rear springs because the original ones were really sagging, to the point where the wheels would rub when I hit major bumps. I replaced the springs, shocks, bushings, u bolts, and shackles. MY XJ is still stock height, although it may be a little higher now in the rear with the heavy duty springs I used. After replacing the suspension hardware, the clunk that I used to get when going from reverse to forward or vice-versa has completely disappeared. The cause must have been worn suspension parts, not my diff or driveline at all. Hope this helps someone!

mtulett1

hey I was wondering what size u-bolts you used? i am doing my rear leafs and they didn"t come with hardware. thanks

leadfoot100

I have the same issue. Haven't looked into the rear diff, but it sounds like its coming from the rear end of some kind.
it's almost like when the weight shifts forward really fast it clunks, but then when I accelerate the weight shifts back and it clunks back into position. I would like to know what it is as well.

lfhoward

I had a shop do the work and my jeep is still stock, so I'm thinking that they must have used the right u bolts for my 8.25 axle. The bolt size is different for different kinds of axles. Here's a page at Morris 4x4 Center where you can choose u bolts by axle type. Scroll down to #22. http://www.jeep4x4center.com/jeep-su...herokee-xj.htm

KD3NE

How much was the bill to replace the springs, shocks, bushings, u bolts, and shackles.

Parts vs labor?

I am about to do an axle swap and figure since I will have it all apart, might as well rebuild as my rear springs are sagging as well.

lfhoward

For me the total came to about $1200, including both parts and labor. I think the labor was probably about 1/2 to 2/3 of the cost, although I don't remember the exact amount. I had the shop order the parts and perform the work because I don't have the heated garage, tools, or mechanical experience to perform such a big job on a rusty old suspension. I am happy with the results, though!