98 XJ8 95k

Situation - Car has always shook from side to side from 50mph-70mph with stock wheels (225/16/60) and even now with 4 all new wheel and tire set I just bought (245/35Z/20). New tires are balanced and in perfect condition. The vibrations (what feel like side to side motion real quick) at those speeds have always been there even with balanced/aligned different new tires over the years, now even with after complete tire/wheel change.

Like stated it has been doing this since I got the car back in Feb 08 (75k miles, now has 95k) it's a 3rd car so wasn't a huge problem. As well, it was a lot more faint with the 60 series tires compared to the 35 series tires I have on now. It vibrates pretty badly through 50-60 mostly and even up to 70mph (passenger seat even shakes quite a bit no good). I don't want to jack up my new tires/wheels because of a bad part. Our speed limits are you 55mph and 70mph so yeah.. ouch! :P

I wasn't sure if I had just had a bent wheel before, and I knew it wasn't a tire because like I had changed all the OE tires before (aligned/rotated as well) I get complete car shaking. It was a bit more faint until I went to a thinner tire. Now it's even worse of course less rubber to absorb the shake. Time to get this fixed.

I'm sure this car has original wheel bearings all the way around (there are no sounds in turning or anything, only the vibrations at 50-70mph. Since it's not my wheels or tires (they've been checked), What else could cause these intense vibrations at 50-70mph? Any ideas guys? Motor mount/control arm or bushings/ball joint/wheel bearings/etc? I just really hope it's not the transmission because this is really the only thing left on this car to fix.

* Also, the shimming/shaking happens at BOTH accelerating and coasting at those speeds 50-70mph. So it's not only when the engine is in use, it shakes all the time at those speeds, but it does get worse of course when you accelerate because it's putting friction on it. Now while it does happen all the time, sometimes it shakes quite violently, and sometimes very little.

 

Axle shaft? Warped rotor? ... lots of straws to draw at. Have you had this looked at by a qualified technician (not just the alignment guy at the local tire shop)?

Do you feel it only in the body/seats, or through the steering wheel also?

Watch carefully when on the highway... does it seem fine for a while, then when going through a long sweeping turn, you feel it come back and stay bad in the next straight... only to fade again in the next sweeping turns, etc.?

 

could also bee rear u joints, they must be lubed (don't know how often)

 

The U joints do have grease fittings which are seldom used outside of dealer service. They should be lubricated at 10k intervals.

You might read the thread on the XK8/R forum under the FAQ sticky 'Suspension'

Here is the direct link but there is a world of information in that FAQ thread.

https://www.jaguarforums.com/forum/s...ead.php?t=5289

 

Thanks for the responses as usual.

Doubtful of a warped rotor (although the back two have never been changed I don't believe, they've been looked at deemed fine about 2k miles ago) but the shaking is felt ALL around the whole car not just from the back. It's everywhere from under the seat, to the steering wheel, to the wheel well, to the passengers side (whole seat shakes).

@ Quad - Well it's always there, all the time, even on the HWY and interstate, anything from 50-70mph+ it shakes. When you say 'qualifed tech' that's basically just ANYONE with an ASE in basic mechanics right? That doesn't mean much anymore, heck the dealership goes didn't know much about this.

As well, it seems like the piece must 'heat up' or something because if you take it down the interstate about 1 mile and get off first, the shaking is not always as bad.

It's gotta be something like the axle, u joints, ball joints, etc. It's always been there, and has never gotten any worse.

 

Outer U joint siezed. Lube won't help.

 

JTO, welcome back, we missed you.

 

So what makes an outer u-joint 'seize' anyways. I mean since it doesn't always shake as bad all the time. How's the car still function with seized up parts, and why would that make it wobble at those speeds only? The shaking varies from drive to drive, but always at the same speeds. 50-70mph. Today it actually wasn't to bad, day before it was horrid. Doesn't make much sense to me.

I see a U-joint is just basically an X made of metal. How's this fail?

 

That X made of metal rides in needle bearings which, especially if not lubricated regularly, will wear out and get very 'gritty' in operation, causing the normal, smooth operation to feel more like alternatively sticking and breaking free, several times per rotation.

THis is a possibility, along with rear (or front) rotors, as they both will heat up under use and, perhaps, start showing the symptoms only when heated. The rotors may warp more as they heat up. Checking runout on the rotors with a dial indicator will tell you whether this is an issue or not. 'Feeling' the u-joints for play or wear will tell you whether they might be contributing.

A way to help isolate is to determine what the vibration frequency is... does it feel as if it's matching the tire's rotational rate? THis would point to tire imbalance, bent wheel, bent rear axleshaft, wheel bearings, axleshaft bearings, brake rotors, etc. Is it faster (2 to 3X) than wheel rotation rate? This would point to engine, transmission, torque converter, driveshaft (prop shaft), u joints in driveshaft, etc. If it's significantly slower than the wheel speed, then it's pointing to wheel bearings.

By 'qualified' technician, I mean someone who specializes in suspension and driveline components... especially import and Jag's. The average tech won't necessarily know what to look for under these unusual conditions - one who specializes has a much better chance of having been there before. Here, in a relatively large town, there's maybe 3 or 4 places I could suggest. For you, a little investigation may be necessary.

 

Hello Stranger!

 

As for the frequency, I'm pretty sure it matches the tire rotation or is slightly slower, it's definitely not faster.

Thanks for the information. I know for the 2.3yrs and 20k miles since i've had the car my u-joints have not been lubed, so no clue. In fact, I don't believe i've ever had to lube a u-joint in the 3 cars i've owned so far. Ooooops haha (was never a problem I guess got lucky)

* I drove it today about 25 miles on various roads 20-70mph. When I brake there is no shaking or anything besides the 50-70mph zones like usual, does that indicate anything perhaps on the rotors? How many u-joints are on this car as well if anyone knows?

 

There should be 2 on the driveshaft and 2 each on the axle shafts.

"When I brake there is no shaking or anything besides the 50-70mph zones" - to clarify, this vibration is there whether you are braking or not, correct? If only when braking, it is most likely going to be a rotor.

 

I have a 2000 xj8 and I have the same problem and the shaking is coming through the steering wheel for me. And It is likely to be the break rotor for me.

 

Have you looked at the ball joints?

 

That's what I meant yes sorry, so that should rule out rotors, it does it all the time even when not braking like stated. Plus, it doesn't get any worse with braking. The shaking zones are 50-70mph and it's all the time at those speeds, while coasting and under acceleration. It's constant, only acceleration in the 50-70mph zones make it worse because it's putting more friction on the failing part (sounds logical).

Probably ball joints or one or more u-joints for me. Good starting place. Is there an easy way to see if a u-joint is failing? Thanks

 

The way I used to do it was to disconnect the suspected shaft at one end and feel how the joint acted through all motions... if it's bad, you'll feel it. Don't know how hard this is to do on the Jag, I haven't done it.

Also, in some cases, the joints get very loose as the needle bearings wear out. You can see this just by rocking them in place - without disconnecting one end of the shaft. If there is ANY noticeable play in a u-joint, it is worn out - and this play can lead to an imbalance that you may feel while driving.

 

Thanks this will be the starting place for my situation. Since it's not the tires or wheels (old set does exactly same thing at exactly same speeds) then it must be one of these culprits. Thanks.

Hey btw did you get your tensioner replacement done with those tools?

 

On my 99 xk8 you get the car off the ground then place your hands at 6 & 12 o’clock position and see if you have movement then try it 9 & 3 o’clock. If you have movement from the 6 & 12 position then look at placing your hand on each U joint to find the one that is in trouble. If you have movement from the 9 & 3 position you may not have a U joint problem you may have a wheel bearing that needs replacement. I hope that makes a little sense.

 

I haven't yet, but it's climbing on the priority list... and will be done soon, now that I have the tools; thanks.

 

Sometimes is the things that you least expect. My car was shaking like crazy between 50 and 70 and it tuned out to be a misfire in one of the cylinders. No it didn't feel like typical misfire. It actually felt like both front wheels were going to pop out. Fixed misfire and now it runs smooth at any speeds. I also have a warped rotor but that's another story since that only makes it shake when I brake.