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About 4 months ago I b ought a 1998 XJ8, 69,000 miles. There was a noise coming from the rear end that sounds like a worn brake pad rubbing against the rotor. The noise only happens above 50 MPH and gets louder as speed increases. The sound is constant and weaving left or right does not change alter the sound. So far I've checked the parking brake shoes and adjustment and checked by gently applying the parking brake at speed with no affect on the noise. I've replaced the following, rear brake pads, differintial fluid with 75w140, left and right inner and outer wheel bearings and races, all 4 axle ujoint. There's no play at the rear wheels at top and bottom or side to side. I checked the output bearings by prying between the diff and flange and there no play. I thought it might be a bad pinion bearing or loose pinion nut so today I pulled the jurid coupling and checked the pinion. No up and down, side to side or in and out play. The pinion had a groove in the shaft and the sleeve on the pinion nut was center punched into the groove so I'm assuming it has not backed out. I did find some wear marks on the pinion shaft where it slides into the driveshaft ( see photo). Is this normal wear or could the jurid coupling be going bad? I cleaned and inspected the coupling and found no cracks. I've put about 2000 miles on the car so far and I'm am still trying to find the cause
Highhorse, thanks. I read that post and the only thing I haven't looked at is the front jurid coupling. It could be the problem but the sound is from the back and I assume if the front coupler were loose of bad the sound would be between the front seats. My daughter has a Volvo 780 and the center dirveshaft bushing/bearing is worn and it has a vibration only during initial acceleration and the XJ8 is more of a scraping noise and only at highway speeds. The next step for me would be to replace the output bearings but they are rather expensive and I'd rather not spend the money on them until I'm sure they're bad. At this point I'm pretty much at the, put up with noise, and "run until failure" mode.
Highhorse, thanks for the advise. I visually inspected them while I was under the car. They looked good but, I'll crawl back under today and give them a closer inspection. My son and daughter both drive Volvos and they have both had that failure and the symptoms were rattling and clunking over rough roads. The Jag only has the faint scraping noise.
Checked the shock seats and bushings along with all the subframe bushings. They all look good. Since the jurid couplings are original to the car and are 23 years old I figure I'll replace them since the rubber may have deteriorated due to age even though they look good. Since I'll be under the car anyway I figured I'd replace the center support bearing. I was going to change the center u joint at the same time but can't get a valid part number. Does anybody have good part number for the propshaft u joint?
I'm still curious about the wear marks on the end of the pinion shaft. There was some residual grease (very black grease) on the pinion stub. I wiped the stub clean so the rings on the stub are discoloration from what I assume ti be wear from the propshaft. I looked at some of the used differentials for sale and none of them have any wear patterns like mine. My thinking is a bad jurid coupling may allow enough play to allow the prop shaft to wobble on the pinion stub and create the marks
The noise is now worse. It's especially bad when braking. The low hiss turns onto a loud metal against metal grinding. The brake pads only have about 500 miles on them so I've ruled them out. I used the parking brake as a test to verify it's not the pads. Applying the parking brake while moving also causes the grinding noise. I also used the J-Gate to downshift and that also caused the grinding noise. I'm fairly confident the noise is internal to the differential. I bought a used differintial and I'm going to swap it out with the original next week. Before I swap them out I'm going to pull the cover off the used one and clean it out. I'm also going to replace the pinion seal since it's a lit eaiser while its off the car. My plan is to rebuild the original and keep it as a spare since the longevity of the used diff will be an unknown.
So my question is I need a part number for the diff cover gasket and a part number for the pinion seal (I have the part number for the seal and yoke as a set but it's expensive) I'm hoping to just replace the seal and reuse the yoke.
You should jack the rear of the car up off the ground and put 2 jack stands under it. Start the engine and press the “trac off” button. Get another person to get in the car and run it up to 50mph in D. Carefully get under the rear of the car and diagnose where the noise is.
Addicted2boost, I did that when I bought the car 3 months ago. Couldn't hear any abnormal noises at that time. Since the half shafts do double duty as the the upper control arms and are placing the wheel and output bearings under either tension or compression while the car is on the ground and in motion I figured the offending bearing(s) may only be making noise while being stressed. I'll put the car back up on stands this weekend and try to identify the location of the noise. From the dirveshaft to the wheels I count 15 bearings and 5 u-joints (plus 2 Jurid couplings) in the Jag driveline. So I'd expect a little more noise than a "normal" car.
Just to wrap up this thread. I put the car up on jackstsnds again and used a 4 foot long 1 inch PVC pipe to listen to the wheel bearings, output bearings and differintial. My wife then ran the car up to 50-60mph. If you place one end of the pipe on non moving piece of metal near the bearing in question then place the other end close to your ear it acts like a stethoscope and transmits the sound fairly well. Both wheel bearings sounded good. I then tried the output bearings, they also sounded OK. When I put the pipe on the differential i could hear a faint grinding noise. I assumed the problem was internal in the diff so I bought a used one for $300. I swaped it out with the original one and the noise is gone. I'm going to rebuild the original one and keep it as a spare since the longevity of the used one is unknown.
Wow, sorry to hear.....that really sucks, but I'm glad to hear you seem to have found the issue. If you don't mind me asking, do you know how many miles were on the replacement diff? Since you went through such lengths, I have to assume you replaced with new fluid as well?
I may guess you may provide a diff rebuild thread as well?
Highhorse, I have no idea how many miles were on the diff. I got to inspect it when I picked it up. No play in the input shaft, or output bearings. The pinion seal was dry with no signs of any seepage and no noticeable noises when the input shaft or output shafts were rotated. It did come with a 30 day warranty so for $300 I took a gamble. I drained the diff and the fluid looked new, but the fill plug was not particularly tight when i removed it so my assumption is the salvage yard drained it and threw in some new fluid. The used diff may fail in 6 months....or 6 years....or never. But for $300 the car is bsck on the road. When I get around to tearing down the diff I'll start a thread on it. I've also got a 1999 XK8 so having a spare diff probably isn't a bad idea.
Xalty, I condidered modifying an X300 diff but there were none to be had locally, and this was the quickest way to get the car back on the road. I suppose i could wait until I find a good deal on a used X300 diff modify and rebuild that one if the used one goes south but then I'd have 2 X308 diffs sitting around. Since I also have an XK8 i figured its easier to stick with the stock diff as a backup. I know the XK8 uses a different yoke but that's an easy swap when the diff is out of the car.
1998 XJ8 noise from rear end.
