I have a 1983 Series III XJ-6 which has vibration at low speed which seems to be worse the harder I'm trying to accelerate. It goes away as I gain speed. It appears to be coming from the rear end and I thought it might be the lateral adjustment on the rear end of the drive (prop) shaft - that's noted in the workshop manual as being a trial-and-error adjustment. I've tried doing that with minimal, if any, success. How sensitive is that adjustment? I started with the mount over to the right hand side (per the manual) and then have moved it over a small amount each time but it may be as much as 3/16" increments. Is there a special way of doing this? I've not had the car long but do know that the previous owner had the gear box out of it so don't know if anything else was changed. I've also checked all the other bearings and U-joints and they all seem to be OK. Any ideas would be much appreciated!

Dave P (in Ontario, Canada)

 

Dave, you are new, so welcome firstly.

My experience with S2 And S3 is usually the centre bearing is going AWOL, as in the rubber casing.

The actual joints of the prop shaft come next.

The trans mount spring and bush fiasco is 3rd, but that is usually a banging vibration/noise on acceleration.

The actual pinion bearing in the nose of the diff, although not a common failure, will cause that vibration, but usually a massive oil also.

I have messed with that adjustment and felt no real changes at all.

 

Which manual?

My Jag manual gives specs for making up an alignment jig. That in itself is a bit of effort, though!






I've been thru this recently, also starting at the right. I used 1/4" adjustments till I felt some improvement and then increasingly smaller increments to center-in on the sweet spot. Not too hateful if you have a drive-on hoist but a PITA if you have to do it on your back.



How did you check the u-joints? You have to remove the shaft to check them properly.

Anyhow, I agree with Grant that the center bearing is a prime suspect.

Cheers
DD

 

Two thoughts. One with some experience, the second with none!

1. Either the front or rear ujoints is just a tad loose or possibly both. Agree, one cant tell without removing it. Once removed, the movement must be slick as silk, anthiong less will vibrate!!

2. The center joint. Why it is there is a mystery to me. I've had trouble with them in other critters. They were LWB mid fifies Chevrolet pickups. I figgerd GM just wanted to use the same rear assemly on SWB and LWB trucks and used a short shaft to extend the torque tube for the LWB's!!

My thought is that the drive shaft must be straight That would indicate that up and down deflection as well as left and right has to be considered and that it be perpindicular to the rear cage to function correctly. Careful measurement and perhaps the use of a level could dtermine that.

Irritating to say the least.

Carl

 

Thanks for all the comments guys - I guess I have to keep looking and be more vigilant on checking the other potential culprits. It seems the vibration is coming from well behind that centre bearing but I realise appearances can be deceptive.

I saw that jig that Doug refers to (it's in Jaguar's own manual) but I believe it only apples to series I and II cars - not the series III. No idea why!!

I haven't done too much disassembly yet (yes - I am doing it on my back and it is a PITA!) but that'll be next on my agenda as soon as the weather warms up here in chilly Ontario.

 

Smooth as silk, yes ! I've had some over the years that were not loose but, rather, just the opposite----too tight, on the verge of seizing up. They'll vibrate like crazy!







Bit of a mystery to me as well, as so many cars do perfectly well without them. Chevy is/was still using them even on modern trucks. I'm sure there is plausible rationale as to "why", with usual pros and cons






Jaguar calls for a certain angularity in the shafts. The "why" is open for discussion but u-joints DO require at least a small angle to work properly and Jaguar is known for complex solutions to simple requirements :-)

Cheers
DD

 

Vibrations can be tricky to iron out. Sometimes a blatant fault isn't visible so you "start somewhere" and just start eliminating possible culprits one-by-one. It can be time consuming.

By the way, if you DO replace the driveshaft center bearing and/or u-joints make sure to mark the two segments of the driveshaft so they can be properly indexed on reassembly. If you don't, and the two segments are installed out-of-phase, you'll be hatin' life!

Cheers
DD

 

Doug:

The need for angularity escapes me. but, that isn't the only one by far! It seems to me the U joints are to accomodate angularity, but to a point. Too much and stuff happens.

My XJ as presently consitiuted uses a one piece shaft . It works just fine.

I agree, at times, simple is as good or better.

Now, if the car has a straight rear axle that moves up and down, I just might understand why a center joint might be smoother. But, in the Jaguar, the engine and rear cage remain pretty steady, so two corrections should be just fine and the added third, more problematical than beneficial.

I've been watching some You tube stuff on home built tractors. WOW!!! But, as it is at a relatively slow speed, some can be ignored. Some real beasts. A couple of Aussies built one using part of a General Grant tank engine!! Everytning probab;ly solid mounting. No need for ujoints!! If any, they would have to be huge to take the torque!!

Love those displays of ingenuity!!

Carl

 

My ser 3 has a GM 700r4 in place of the original BW66. I installed a new one-piece drive shaft when I did the Trans swap. I noticed that the new shaft runs pretty close to the right side of the transmission tunnel to make the connection to the differential with its offset input pinion. I'm guessing that Jaguar deemed that clearance too tight and incorporated the two-piece. The geometry of the stock set-up seems to get the rear part of the driveshaft farther away from the side of the tunnel.
Just a theory...

 

I had a rumble noise develop that turned out to be the drive shaft center bearing as the issue. Heard the rumble driving at low speeds and at higher speeds it would smooth out. To investigate I sat in the rear of the car with the driver, my son, drive the car. I put my hand and ear down at the drive shaft tunnel and could easily confirm that is were the rumble was coming from. On some forums it was said to look for torn rubber on the center bearing but when I looked my rubber look perfectly good so it through me for a curve. Drive the car again and could once again easily confirm it was coming from the center bearing. So I took the center bearing off and put in a new center bearing and the rumble was now gone for good, back to a nice and smooth ride.

Here is what I discovered. My center bearing rubber looked perfectly good on the car and even when removed from the car the rubber was not torn, BUT I did notice that the center bearing rubber was drooping down quite a bit, something you can not see when it is on the car at all. The drooping changed the drive shaft alignment enough to cause the rumble to occur. So just know that this drooping of the rubber bearing can and in my case did cause the rumble. The metal center bearing was spinning smoothly so did not seem damaged.

New center support bearing was a Moss EBC9040 for my 1983 Jaguar XJ6 Series 3 Vanden Plas.

Here are some pictures to help see what I mean.


Center Bearing on the car looks normal.



New center bearing nice and center with rubber.



New center bearing on the other side nice and center with rubber.



Old center bearing rubber drooping down towards the nut side.



Other side of old center bearing showing the rubber drooping down towards the nut side.