I developed a rear end noise that has gotten worse very quickly.

It started out sounding like a dragging brake pad or parking break. I checked the adjustment on the parking brake and insured the calipers were moving freely and every thing was moving freely there as well.

I did the tire wiggle and didn't note any bearing play. I had recently changed the diff fluid and it is at the proper level and I noted a small amount of metal on the drain plug but nothing I felt was substantial. The fluid did look to have some moisture in it. So I cleaned the breather as well. No signs of leakage on the rear end.

I also lubed the uj's on the half shafts. I noticed no play on the those of note either.

All this made no difference in the noise level of the rear end still sounds like a brake dragging.

I started to pick up a vibration on Friday, around 40-50mph seems to shake the whole left side of the Jag. Also noted a slight metallic rattling sound at that point.

Up on ramps it goes. Checking out the underside I found the front UJ on the driveshaft has a small amount of slop in it. I picked up new UJ's and I'm starting the tear apart on that this afternoon(trying to get motivated to freeze my butt off). The rubber coupler disc looks fine at the driveshaft to diff connection.

The center support bearing looks to be in good condition from a visual inspection. I will of course take a better look at that when I get the shaft out. After the driveshaft uj's I will probably see about pulling the rear hubs to see if I can note any problem there with the bearings.

What else should I be looking at guys? What am I missing or overlooking? Anyone else had a similiar condition?

Thanks in advance.

 

Based on what I read, your front driveshaft coupling bolts are loose (play, not causing any symptoms) and you have one or both differential output shaft bearings worn and making noise.

 

Thanks, I'll check those bolts. How bad are those output shaft bearings to do?

 

So has anyone done the output shaft bearings? If so any tips or pointers

 

the output shafts are easy to change (30mins tops) but to remove the old bearings is a bit of a ******* unless yer have proper stuff. you can do it using a grinder or some folk have used a drill, to drill a series of holes in the collar.
I prefer the grinder method so long as you are careful and not damage the shaft. to fit the new bearing you really need a press
there's a chap in Berkshire Engerland wot will do you an exchange shaft, you send him yer old one and he'll send you one with a new bearing etc. not much good to you but it is for anyone in Blighty


jack up yer car etc,take wheel orf, undo the bolts holding the drive shaft to the output shaft, then undo the bolts holding the output shaft in the diff, it should now pull out

 

Thanks, I'm hoping to get to work on it tonight. I'll probably take the shafts and the bearings to a machine shop to have that done there. Better safe than sorry

 

i get me 15yo old son to whip em out, then 10mins wiff the 41/2" grinder followed by 2 mins on the press then back to him fer refitting

 

We'll see how it goes lol.

 

Greetings Army,

It's tough to say what you are hearing and feeling from the description, so I don't want to lead you to any false conclusions. As for driveshaft symptoms and faults, the loose front coupling bolts are likely to be the play that you are feeling upon inspection, but not causing any noise or vibration. You will sometimes get a "clunk" when shifting from D to R, but that's about it. They are a bitch to get to, 9/16" universal socket and a stubby box wrench on the backside if they're really loose.

The six bolts for the Rotoflex coupling at the differential end of the driveshaft can come loose, I just had one the other day where one of the bolts was WAY loose and you could watch the donut pulling away from the diff pinion flange when rotated. That 1990 XJ6 had intense vibration at about 45 MPH which continued to increase with speed. Tightening up the coupling bolts helped, but it was still there. Like 80 ft. lbs., 19MM on the bolt and the nut. The customer did not want to spend any money, so it left unresolved. The Rotoflex coupling was not cracked, the center support bearing rubber still felt pretty sturdy, and the transmission mount looked to me like it was sitting a little low. I noticed on the last road test that there was a pronounced vibration underfloor at about 35 MPH on decelleration, a quick "brrrrrrrrump", which is a driveshaft vibration for sure.

The U joints on these propshafts almost never go bad.

Output shaft bearing noise and eventual failure are very common on XJ40, but I wouldn't characterize the symptom as vibration. It's a growl from the back, increasing in noise with road speed, and is constant on or off the throttle. The output shaft bearings don't have to be worn enough to yield "play" when you tug on the wheels: they can make noise just fine even when there is no lost motion. The source of the noise is difficult to pinpoint for me, even with the car running on a rack in D and stethoscoped. You change the one you think is noisey, and sometimes find that you made things better by exactly half.

Differential pinion bearings also go bad on these units, and result in ring and pinion misalignment. You can differentiate the source of this noise on a road test, as there is a marked change in the pitch of the noise when you lift off the throttle at highway speed. That means a rebuilt diff.

Worn output shaft bearings shed steel particles into the diff, so I'm thinking that's what you saw when you changed your gear lube. These particles are what cause the pinion bearings to wear too. Additionally, some folks incorrectly refit the pinion flange when replacing a leaking pinion seal, and the pinion bearings eventually fail as a result of incorrect bearing preload. True on later models as well.

One cool test is to find a section of road with a couple of small whoop-de-doos, there's one close by me nicknamed "Seven Hills Road". At 50 MPH, when you crest each hill, the rear suspension gets unloaded and the noisey output shaft bearings get quiet for a moment, untill you're over the hump and they get loaded again. That one is a dead give-away that the driveshaft and differential pinion bearings have nothing to do with the noise. An outer hub bearing could still be the culprit, but usually they have noticable play at the wheel when the are worn enough to make noise.

So I would drive it some more, listen some more, and look around some more before I started tearing anything down. One other thought would be to drain the diff again, if you have some more flakes you know you're looking in the right cereal bowl. I'll post a procedure for the output shaft bearing replacement in a minute.

 

I forgot to add to this thread that I did find that the bolts were a bit loose on the prop shaft. I have not done any significant driving of the Jag since tightening those up. I however did note that when playing with the shaft the slop I had noted seemed to be gone.

That is what has led me to the rear end. Tomorrow I will re-drain the rear end fluid and see what comes out.

 

As for changing the output shaft bearings...

Grommet is right about only having to unbolt the axle (halfshaft) flanges. Use lots of penetrant, and a thin wall 11/16" socket. No need to hold the stud, just remove the four nuts. HOWEVER: you have to employ some method of limiting the axle travel once unbolted, or you will stretch the caliper brake hose. Not good. You can tie up the hub with a piece of rope or mechanic's wire to the rubber bump stop in the top of the wheel arch to hold the hub carrier and axle shaft in position, just don't stretch the brake hose. There is enough slack in the emergency brake cables that they will be unaffected in this position. Slide off the spacer (right side) and the spacer and speed transducer collar (left side).

Five bolts hold each output shaft assembly onto the diff housing, 5/8", tight all the way out from the needless locktite. Rotate the flange to reveal one bolt at the time and remove it. You often have to lever the flange to remove the assembly from the diff, no drama. There are preload shims installed in the diff housing for the output shaft bearings, pull them out and clean everything up. I never worry about measuring/ resetting bearing preload by altering these shims: my opinion is that they are selectively fit to compensate for machine tolerance differences in the differential housing and the output shafts, and that bearings will be close to identical. This approach has not failed me through hundreds of replacements, just don't lose a shim and you won't have a worry.

There is a large rubber O ring that seals the output shaft seal housing to the diff case, I neglected to mention this earlier but it comes in the kit, along with the bearing, output shaft seal and the retaining collar.

This next part takes longer that five minutes to write, and to execute. You can't press the retaining collar off the output shaft without splitting it first. The manual says to drill the collar and split it with a chisel, that's one way to cook the egg. Grommet's is another, you can grind it: I use a cutoff wheel in a die grinder and make a diagonal slice, then shove it off with an air chisel while the flange is in a vise. MAIN POINT is that you don't want to drill or cut all the way through into the output shaft, it isn't much harded than the collar and you don't want to take much out of it. I've never seen one snap, but damaging the shaft could possibly lead to a crack somewhere down the road.

Now you can support the assembly in a press and the seal housing presses the bearing off the shaft. Remove the seal, clean the housing and shaft, make sure there isn't a nice groove worn in the shaft where the seal was tracking. I pack the new bearing with high temp grease before installation, they don't get alot of lubrication when the diff is running down the road and they can't start out dry. Press the new seal in the housing, slide it on the shaft, press on the new bearing first and then the new collar.

I clean the side of the diff housing with Scotchbrite, and use a wipe of silicone sealer and the new O ring. Don't forget the preload shims, a little grease on them helps keep them in place. Slide in the output shaft assembly, 45 ft. lbs . is fine for the bolts, the locktite is up to you. I don't use it there, and never have found one of those bolts loose with or without it.

You'll lose a little gear lube. One other small tip is to use Teflon tape on the drain and fill plugs: they are pipe thread, so this is completely appropriate, is an effective sealant, and makes subsequent removal alot easier. I think that's about it, like 1.5 hours a side but I'm not 15 anymore and I don't like having to say "we couldn't find the time to do it right, but we found the time to do it twice".

 

Excellent write up JagTech much appreciated

 

The techs are so helpful on this site! : )

 

I'm glad the techies are here...best advice I could give for a noisy rear end was to try some Gas-X.
Can't fart with confidence!

 

Well I drained the diff fluid and have found more shiny metal stuck to the drain plug and the diff lube seems to have a glitter quality to it that I had not noted on the previous drain and fill. I would guess-ta-mate that the amount of metal on the plug was a least a 1/3rd more than last time. Plus whatever amount is in the lube itself.

From the sounds of your earlier write up JagTech, I'm a believer that the output shaft bearings are the culprit. I'm starting the attempt at removing one now for inspection and will post my findings as soon as I can.

 

To add I started the half shaft removal but started running out of light and pb blaster lol.

I also remembered to check the pinion for any notable slop with the prop-shaft still attached and couldn't note any there so maybe that's my happy thought for the day

 

Thank you Uptown and Throttle!

Army, I think we got it figured after reading your findings. Don't be too alarmed when you pull the output shaft assembly out and can't find anything really obviously wrong. If you clean and dry the bearing, that might be the only time you can feel the roughness, but it translates into bigtime noise when you're rolling down the road.

That much metal flake is likely from the output bearings, so it's wise just to change both sides and be done with it.

 

That's the plan, unfortunately it's back to work tomorrow so no playing with the Jag till sat. With a little luck I'll get the shafts pulled this weekend and get the bearings ordered from you next week.

 

Roger that

 

Thanks again for all the guidance JagTech, I owe you a beer sometime.