Hello all. I recently purchased my third Jag, a ’95 XJR. It came with a matched set of BF Goodrich Comp T/A tires in the stock 255/45r17 size, on stock rims. They had good tread on them but they were very old and hard as a rock. Poor dry traction and downright scary to drive in the rain (along with a terrible ride. More like an old 4x4 truck than a Jaguar.) The car also followed every little imperfection in the road (Tramlining as I understand it) and had a lot of road noise at any speed over about 20 mph. After bringing it home I found both front wheel bearings to be in bad shape. Swapped them out, adjusted them as recommended and the road noise was only marginally reduced, tramlining may actually have gotten worse!

Fast forward a few weeks and following the advice on one of the Jag forums (possibly this one, I’ve forgotten) I downsized to a 235/50/17 tire, as supposedly the stock tire size belongs on a rim ˝ inch wider than Jaguar put them on. WOW! It’s a completely different (Improved) car to drive! Zero tramlining on the same roads, so quiet I can hear the wind gently rushing by at speed. Handling is great. Best part is the ride, its smooooth…up to about 35mph. There in lies the problem. I have now uncovered a vibration that was probably there before, just masked by the crap tires.

Its starts subtly at about 30-35mph but by 45 it’s heavy and strong. Odd part is going faster seems to make it fade away and by 65 its still there but minor. Oddly, it also seems to be worse in the cold. Yesterday morning was 15 degrees (Fahrenheit) and I really felt it on the way to work. Not as bad on the way home when the temp was 40 degrees. Maybe the oil in the shocks was just thicker due to the cold? It doesn’t get any faster in pulse with speed, just stronger then it fades at higher speed. That makes me think driveline, not wheels or tires?

What do you all think?

 

I THINK you may have a tire problem. From your description, it soumds like a tire with a construction or other mechanical problem.
Do you feel the vibration your seat or the steering wheel? That points to whether its the front or the rear axle. I might start where you bought the tires-see what they say. The reason vibrations come and go with speed have to do with the resomances of the system,in this case the car body.
Other possibilities are the Jurid coupling on the driveshaft or the drivshaft intermediate bearing.
Good luck

 

Thanks Ross, I always forget the name of that bad boy.

We are assuming that a full balance and alignment was done after the various tyre/bearing changes?

One of my thoughts was worn track rod ends, if it had been continuously pulling against them for a long period of time and now it no longer is.

 

Thanks for the suggestions so far. I can have the balance re-checked by the tire place easy enough, although I did tell them I was easily annoyed by vibrations from poor balance when I dropped it off. I’m not sure if a perfect balance would rule out an internal defect in one tire causing it though.

It’s definitely felt through the whole car, seat, floor, steering wheel. Like I said the frequency doesn’t increase with speed, just the intensity. Then it fades as speed increases.

Today on the way in to work I slipped into neutral to see if it was engine related and there was no change, so I think I can rule out any Harmonic balancer or misfire issues.

As far as frontend stuff, I did not get the alignment checked after I replaced the front bearings. I did check ball joints, tie rod ends, shock and control arm bushings for play or damage while I had the car off the ground for that job and all seemed fine with no discernible play or looseness.

That Jurid coupling interests me, I forgot about that being there. The car only just turned 80,000 miles after I bought it, but it is 17 years old. The rubber could be degrading from age and lack of use and starting to fall apart. (I drive it daily since I bought it, but it was a occasional weekend, nice weather only cruiser most of its life before that)

If it’s somewhat warm in the garage this weekend I’m going to check that.

Any other thoughts?

 

That part about the frequency not changing with speed is particularly unusual. Are you sure about that? really SURE???m Really, Really SURE???
If that is true, then about the only thing I could think of is a very bad alignment causing scrubbing, in which case you better get it fixed while you still have sone tread on those nice new tires.

 

A crude but perhaps revealing experiment would be to swap the tires front to rear. If this changes the characteristics of the problem you can feel fairly certain it's a tire/wheel issue. However, no change in characteristics doesn't necessarily rule out a tire problem.

You might want to seek out a tire shop that has a "Road Force" type balancer. Not only can this solve some weird balancing problems...if you have any... but it can pinpoint a defective tire. If nothing else it can rule out tire/wheel issues so you can pursue other paths.

I myself have picked up a feel-it-thru-the-seat-of-my-pants vibration on my XJR, starting at about 50mph. The frequency is such that I feel it as a tingling sensation....not a shimmy or shake. I'm leaning towards driveshaft bearing, u-joints, or Jurid coupling but, truth is, I haven't dug into the problem yet.

Unless they're on the verge of self-destruction....in which case you'd have a gross vibration....the only way to properly check the center bearing or u-joints is to remove the driveshaft and feel the action and smoothness of the joints and bearing. Considering that removing the driveshaft isn't a 5-minute thing you might wanna have new parts on hand.

I have no experience checking Jurid couplings. I suppose impending disentegration would be easy to see but I don't know if minor surface cracking/deterioration of the rubber is enough to condemn the coupling. Hopefully others will chime in on that.

Keep us posted.

Cheers
DD

 

Ok, so it was warm enough and I spent some time in the garage under the Jag this weekend. I found what I suspect to be the problem; on the bottom side of the transmission mount the rubber bushing is completely gone. This leaves a space of about an inch and a half or so that the transmission can bounce up and down when I push up on the front section of the drive shaft. It even continued to wiggle up and down a few times after I stopped. After looking at the diagram of how it works I see there is a spring on the top side (in the parts catalog item #MMC7553AA is what has gone missing). I can see this getting into a resonance and possibly causing my issue, fingers crossed. I will order a replacement and install it on the next warm garage day after it arrives. The Jurid and the rubber around the center driveshaft bearing look to be in perfect shape by the way.

While I had it up in the garage I also double checked that my wheel bearing adjustment had not changed (It hadn’t). Checked the new tires for any sign of wear or scrubbing (None found, still look new). And I followed I think it was Doug’s advice to swap front to rear. Still had the vibration, so we will see if the trans mount repair fixes it.

Oh, and sparkenzap, I’m pretty sure…well, kind of sure…uhmmm…almost maybe positive that it probably most likely stays the same frequency throughout the speed range....for sure...I think.

Thanks for all the suggestions so far fellers, I will update when I get the part installed.

 

Glad you found that. You have probably found the cause of your vibration since there is not much else that could make a speed independent vibration. The fact that it was true (the part about being unrelated to speed) made the things we all said to look at (including me) pretty much unlikely. Who would guess that your engine. transmission was acting as a tuning fork?

 

It would be really interesting to hear the final result.

 

Well the part came in and my garage was above 50 degrees inside so I fought the good fight and changed the transmission mount insert. It was not hard to do. I did have some issues getting the old one out, but in the end I was able to work it out with a dental tool hook and a flat screwdriver. As you can see from the pictures it was shot.













The new one slipped relatively easy with a liberal coating of dish soap on it for lube.




It still seems to have a gap between the washer and the mount though…can anyone check theirs to see if this is normal? I’m thinking now that the spring on the topside of the mount (#11 in the diagram, #13 is what I replaced) is weak and cant hold the transmission up at its proper height.



Oh, and the vibration is still present.

 

I am no jag expert, but I have had a few bmw 5's and 7's and when having issues at that speed, it was always related to the front end. Rear end issues occur at higher speed. If your bmw shakes at 50 mph, you always check everything from the front wheels and up. Even just some dirt buildup on the mounting surface of the wheels is enough to cause the problem you describe.

Check everything steering related, and check it again. Use a crowbar to apply force, as the weight of these cars can make it really hard to detect wear.

 

Some gap is normal....er, at least my car has a small gap even after replacing the rubber pieces and using the uprated #11 spring.

I've had 3 Jags. All have had a somewhat loosey-goosey transmission mounting arrangement. Hard to determine how much is "too much", though. What you have now is probably as good as it gets.

Too bad it didn't fix the problem but you gotta start somewhere.

Cheers
DD

 

Wow.
That does not leave many places to look for a vibration that is not speed dependent. Considering that you had what I think was particularly bad tramlining, I suppose looking for something related to front end scrubbing is in order.

Sounds like sbc's crowbar suggestion is next.

 

Have you checked the vee mounts yet? Unlikely I suppose as the tramlining is gone but its worth a look

 

Picking on you only because you have both the car, the skills and a hoist

But, did you know that there is a driveshaft alignment procedure? It involves 3 pieces of string and 3 plumb bobs.

It is outlined in the 1995 MY section of JTIS for the X300. Presumably it would also apply to X308 because of the similarity in design.

Then try this link:

Driveshaft Rumble?

and this other link:

Driveline vibration - shudder - 1961-1962 Cadillac Owners Group (the XJ specific solution is mentioned)

It seems driveshaft alignment has not been mentioned often when people are looking for these 50mph rumbles. Fingers crossed, because I have it too

 

plums, where in the JTIS is this found? I have a copy but didn't find any info on the prop shaft. I do not have a hoist in the garage, but I would like to read up on it. The links you provided seem to say that the symptoms of the prop-shaft misalignment are engine load related, mine is unaffected by that. Even slipping into neutral doesn't change it any. Strange. The only thing I can add is now (after driving it for a couple days since I replaced the trans mount) is that maybe...just maybe... I feel it a little more strongly in the steering wheel than in the seat or floor than before. I need to take a good long ride in it this weekend. Its only 6 miles to work for me on back country roads full of kamikaze deer this time of the year. That makes it hard to concentrate on testing. After that I guess its on to the crowbar checking of the front suspension points as suggested by sbc.

Are you referring to the control arm bushings in the front suspension or something else? I want to make sure to follow up on any leads to fix this. I hate vibrations.

I will report back with any results.

 

blackxjr,
no its something else check this out
XJ40 • View topic - VEE MOUNT CHANGE (HOW TO)
the xj40, x300 and x308 use the same part

 

In section 3/driveshaft alignment, 1995.

Be sure to read all of it because there are a few spots where someone might be tempted to just skip ahead.

eg.

Be sure to read the cadillac thread carefully and note what the XJ expert from NZ says about "always to the left". This implies that it has been seen frequently enough to be able to say "always".

Also download and read the Cadillac factory PDF in that thread. It discusses the interaction of engine speed, drivetrain load, and road speed with respect to diagnosis of the various sources of this kind of problem. Lots of wisdom that seems to have disappeared from contemporary education.

It is interesting that this forum is riddled with complaints about vibration in the 50mph area, and that the driveshaft layout is pretty much the same between the X300 and the X308, yet there is no mention of driveshaft alignment in JTIS for the X308.

 

Yes, familiar with the drivesahft alignment thing. Or, more accurately, I'm aware there's an alignment procedure. Never have done it, personally.

It's certainly worth considering and checking although I'm not sure how it can come out of alignment unless someone has replaced the center bearing and failed to mark the position.....

On second thought, there's probably a vertical consideration as well...which might relate to the trans mount

Hmmmm.

BTW, Greg Meboe...author of the info you linked...is still in Washington state and still playing with Jags. Smart guy.

Cheers
DD

 

Maybe you could give him a nudge since he is the guy with actual experience of the problem. He knows exactly what it feels like in the car.

Consider that in the cadillac thread and the cadillac factory document, all the adjustment movement was vertical ... after centering the longitudinal and lateral base points.

There *might* be some connection with road force balancing since the balancing would have some effect on a driveshaft that was whiping around, although it is several elements further away. Hence, the popularity of road force balancing when hunting these things.