Esteemed X308 colleagues - I've uncovered an issue with my 2000 XJR that has me a bit stumped. As background, the chassis has 111k miles currently and until I got it for the LS swap, it had sat for several years in south Texas heat and sun. The original engine, transmission and driveshaft where replaced with an LS3/6L80E combo, with custom one-piece driveshaft using kit from Jaguar Specialties. As I've been refining the tune for drivability over the past 2k miles, I've slowly been uncovering other things that need attention, but this one has me at a dead end.

My car has a vibration from the rear of the car at 50-60mph+, which increases somewhat with speed, but does so more dramatically after lifting off from strong acceleration at speed. The vibration feels "strong" in that it's steady and under light or part throttle at speed it subsides. At sustained higher speeds, it almost "thrums", if that makes sense. It's almost best described as classic rear u-joints being bad. BUT - they're not. Everything from the transmission to the differential is new (one piece driveshaft, Spicer u-joints, etc) and I just had the driveshaft out and rebalanced on Monday. It's now smooth as glass to 3,000+rpm on their machine. Everything related to the driveshaft is tight and true. There are no other suspension clunks, squeaks, clanks, knocks, bumps, thumps, etc.

Trans mount, engine mounts are all good. There's no engine/trans to body contact anywhere, nor is there for the exhaust. Axle half shaft u-joints look good as well and have been lubricated. Rear shocks (green Bilsteins) are new, donuts replaced when they were installed. Diff fluid changed 3 weeks ago with current spec for listed viscosity. No metal or untoward symptoms in the fluid when that was done. No leaks at pinion or axle shafts either. Wheel bearings aren't making any noise and the bushings at the rear all look ok.

Tires are new Pirellis and they were just rebalanced today (Hunter road force) and I know that made a slight difference because a) the weight pattern on the rims is different in both amount and locations and b) the vibration feels to be of a slightly different frequency now, but it's still present. Tire shop didn't indicate any issues with rims either.

If I hadn't just sold my 2001 XJR, I'd have swapped the entire rear subframe into this one as that car was smooth to 100mph+. But, that has a new home in Indiana now.

I'm open to any/all suggestions from the group - thanks in advance!

 

You’ve certainly done your due diligence addressing as much as you can. One thing I’d like to know is, what’s the driveshaft angle? You’ll need a magnetic bubble gauge for that.

 

Thanks for the feedback, I'll pick one up and shall report back. I don't have a lift so will have to do this the old fashioned way, laying on the ground...

Also, it occurred to me last night after reading your post that the driveshaft may be too long and is binding up at the front where the slip joint/splines are. Reason for this is that is exactly where the driveshaft was out of spec when at the shop. It was out of round at the neck and very top of the tube. As I've tightened up the suspension with the new parts, the rear is perhaps moving around less (correctly so) and over the past 2k miles of driving, this has stressed the driveshaft at those points. That would certainly give the vibrations I'm experiencing. Not sure why it didn't occur to me earlier when I saw where the driveshaft was tweaked. Based on this theory, I'm going to remeasure the length between the front flange adaptor (bolted to the transmission) and the rear one (bolted to the diff) and confirm things with the driveshaft shop, and will snap a pic of how much of the splined area is showing when in situ.

Stay tuned...

 

So, the "driveshaft is too short" theory is inaccurate... Plenty of room at the slip joint connection as shown in the first picture below.

When I measure the driveshaft angle with my handy-dandy new digital angle finder, I show 3 degrees with the car sitting on the ground. My garage floor has a 1.5 degree slope (thank you cookie cutter suburban home builder!), so I'd say that gets me to the target 2 degrees, correct?

After speaking with Andrew at JS, he indicated that engineered the driveshaft angles to have 0-2 degrees to the center bearing on the OEM driveshaft to ensure the Jurid coupling at the differential would remain at 0 degrees. Based on his comments, I'm going to check the seating of the machined adaptors at both ends. He said he's seen the front one not always sit flat on the center nub from the 6L80E output flange. If so, I'll just chamfer that hole and go from there. Will be fun (not) getting to the bolts that are on the transmission side of the adaptor. I will loosen and lower the transmission crossmember to try and get room for the wrench, let alone my hand, in there.


Plenty of space for flex here. I suspected as much, but - seeing is believing. The top arrow (pointing down) is towards the rear of the car. It is at this weld, and the machined neck, where the distortion was. If the front flange adaptor is, in fact, not seating flush, I think it'd stress the same area of the driveshaft...

This is the front adaptor to the driveshaft, looking towards the front of the car. Lowering crossmember looks to be the easiest approach to getting at the nuts that hold the countersunk bolts on.

Rear adaptor looks good as it sits. Once I see what's up with the front, I may as well remove and check this one...

 

If I’m not mistaken, I believe pcolapacker has the same layout as you? You could ask him if he’s had any problems with his driveshaft? ½° to 3° is what it should be in so I believe you’re good there. It shouldn’t be lower than 1/2 or higher than 3. You could check runout at both of the flanges but you’ll need to have the car up on jackstands and in neutral to check. Oh, and a runout gauge setup.

 

Yep, Keith has identical setup as me (minus the camshaft) and he's not had any vibration issues. According to Andrew @JS, some of the 6L80E setups have needed the chamfering, others didn't. There are only 3 of us with the LS 6.2/6L80E in the wild, so not a lot of caselaw on these. That said, as shown in the pics below, mine definitely needed chamfering as it most certainly wasn't seating fully against the trans. It is now...

BUT - it hasn't fixed the issue. I took it for a spin and focused on speeds above 50-55, which is where the vibration really kicks in. I still feel it through the body, and the outside mirrors vibrate. Still feels like it's coming from the back end of the car. Under acceleration has a slightly different vibration and resonance than when I lift off the throttle. At 60-65 if I shift into neutral, the vibration actually gets worse until I put it back in gear, when it damps down a bit. Revving the engine while in neutral and coasting at speed doesn't change the speed or pitch of the vibration at all. The transmission mounts (crossmember, adaptor plate, rubber trans mount itself) are all tight. No weird noises when shifting forward/reverse/etc.

I'm starting to really hone in on the differential itself being the issue given the on/off load behavior of the vibration, but it gives absolutely zero external indication of anything being wrong. Thoughts?



Thanks to stubby wrenches, I didn't have to lower trans or crossmember. Flange was very tough to get off, which surprised me as it slid right on.

Aannnd here's why it was hard to get off. The scoring on the back here shows where Andrew at JS said it might not have been fully seated on the transmission.

Back (trans side) also shows that it was not making as much contact as I'd have expected.

I created the scoring line here by pressing the adaptor against the transmission to see where it needed to be chamfered.

I used the score line as indicator for where to chamfer the adaptor to clear it.

Blue ink shows no contact now and the scuffs around it show that it now seats fully against the transmission. I was pretty optimistic at this point while putting things back together.

 

How about drivesaft itself? Could it be slightly un centered? aka faulty? Keep magic marker very close to the shaft and spin the shat. Marker marks the highest point of the "bent". Shaft needs to be not straight aligned as you probaply know. Especially long driveshafts are balanced differently so they may be clearly bent from the centre and still do not vibrate at all.

 

Driveshaft was examined by reputable shop and is now fully in spec. Outlined what was found/done in the first post in this thread. Not sure what you mean by "shaft needs to be not straight aligned"?

 

Maybe he was thinking it could’ve been slightly bent or perhaps the shaft was slightly welded off center? Just a thought.

 

Gotcha - driveshaft is confirmed ok after visit to driveline shop on Thursday. Their words: "smooth as glass to 3,000rpm+ on the machine".

Have spent the last several hours searching this and other forums and am now focusing on the diff, despite lack of obvious symptoms from there.

Next step will be putting car back up on jack stands (I don't have a lift) (re)confirming proper rear wheel play, (re)checking parking brake adjustment, etc. I then plan on running it with/without wheels to see if I can actually see anything moving, vibrating etc. Am still open to ideas from the collective wisdom here, it's all very much appreciated!

 

From 99’-05’ I worked as a tech at a Mitsubishi dealership. There were a handful of guys who had been there for years…. I was working on an early to mid 90’s 4 door Mitsubishi front wheel drive car that had a vibration on the highway and when you let off the gas the vibration became worse. I checked everything that I knew could be a potential problem. I found nothing. One of the old techs comes over and is looking around and asking me questions. At the end he said that the issue is an inboard cv joint. I said there was hardly any play in it. He looked at it and said there was enough. It was the longer of the two axles that I replaced and I was totally schooled.

What I’m getting at is to check the U joints as well. It’s also possible that one of the output shaft bearings could also be bad.

 

I have come to the same conclusion. I now have 4 u-joints on hand, as well as the necessary axle nuts. I will be replacing all 4 u-joints on the half shafts at some point this week/upcoming weekend. Will report back. Much appreciate the insights, as always.

Also (off topic) - your description of the old school techs reminded me not only of the ones that taught me about air cooled VW quirks when I was in my early teens, but also of an excellent book I read that resonated deeply about how professionals in the automotive trade learn and refine their skills over time. It's "Shop Class as Soul Craft - An Inquiry Into the Value of Work", by Matthew Crawford. One of the best things I've ever read...

 

As these cars age we all need all the skills and intuition we can get.
This forum is a treasure trove of such useful information.

 

So I had a chance to start on the half shaft u-joints today and when I began (right rear) all was going as expected until I had loosened the hub and pivoted it away from the half shaft. The inner reluctor wheel, seal and bearing basically fell out the back/were totally loose. There was also less grease on the bearings than I expected to see. Pic below for reference. Question for the group as I've not had one of these assemblies apart before: is this expected or could my seals have dried to the point that they were loose and allowed things to "walk" under torque/rotation? I thought this was all supposed to stay together as an assembly.

I did not previously notice wheel bearing noise before and the roller bearings themselves and races look ok, save for the gnarly grease. The vibration is definitely occurring at lower speeds now, 45-50mph when I had it out for a short drive today. As the races and bearings are pretty cheap, I have a full set for both sides on their way proactively. Thoughts?

Also - there's a short video below that shows the rotational "play" I have when I turn the half shaft. There is no up/down/front/back play. Is this normal? Again, haven't had one of these apart to this depth yet. The u-joints are all tight, zero play at the crosses/cups/etc. My gut tells me it's ok.


The reluctor wheel, seal and outer bearing were basically sitting here when I pulled the half shaft out. Races look ok though... Plastic from outer seal itself was very brittle/dry

Stub axle came out easily, grease was black, spacer slid out, no shims. Looks like seal may not have been doing its job though, based on the fluff on the back of the flange.

With grease cleaned off, looks to be in ok shape, right?

Bearings had less grease than I'm used to seeing and it's a bit dirtier than the tan grease elsewhere in the hub/on the bearings.

Rollers look decent, certainly not massively heat scored, etc...

 

The abs reluctor is supposed to be a press fit onto the end of the hub. You mentioned: spacer slid off and no shim(s). There’s supposed to be a shim (that comes in various thickness) as that’s what determines the 12 & 6 o’clock end play. In my experience if there wasn’t a shim, it’s because someone has been in there before and what happens is that the shim gets stuck to the wheel bearing via the grease and the bearings get thrown away for new bearings….. that don’t have grease or a shim stuck to it. When you do the other side, look at the insides of the wheel bearings for a shim.
@motorcarman @M. Stojanovic
Have one or both of you heard of the rear wheel bearings never having a shim from the factory and it was setup correctly?

I saw the short video and I think it looks ok but, the 2 guys above may have a better opinion than I.

 

Thanks for taking a look! I've not yet taken the other (left) side apart, I instead dove into part number research and saw that the part number that's on the actual right rear hub casting is MJA3290AA which comes back as a regular XJ8 (and lots of other models) hub carrier. According to multiple sources, including SNG Barratt, the XJR-specific version is supposed to start with MXD, or - more specifically be MXD3290AA for the right rear. Left would be MXD3291AA. If that info is correct, someone has most definitely been in there. The missing shim was interesting as everything I've read here and elsewhere says there's supposed to be a shim in there and it's definitely not on anything here.

I took some more pics and saw that there are thin vertical line markings in the races, most easily visible on the outer side. Leads me to believe that whatever happened, the bearings did definitely leave marks in the races from sitting for so long. That this car has had 11 or 12 owners before me (I have the CarFax and it was passed around A LOT) certainly didn't help for consistent maintenance. That it also wouldn't go over 15 mph when I got it would have hidden this issue for sure, but it's certainly getting worse the more I drive it. When the swap was first done, the vibration first presented at 80-85mph. Over the past 2,000 miles, it's come down to presenting at 45-50 now.

I've ordered good, used units (with 90 day warranty) hub units for both sides instead of doing the bearings and trying to figure out what shim "should" have been there. They may arrive as soon as this weekend and I'll check them out closely before installing and go from there.

I am curious about the different part numbers between the XJ8/XK8 and XJR/XKR versions though. I suspect that the XJR specific one may have slightly thicker casting and/or different durometer bushing for the pivot but otherwise are the same. SNG Barratt lists both versions as fitting XJR/XJ8 for the entire 1998-2003 run. Jaguar Palm Beach parts lookup only shows that the "normal" version fits the 2000 XJR. Weird...

The two pics below show the vertical lines I referenced, one is cropped to show them up close.


Outer bearing race where, if you zoom in, you can see the vertical marks I think are from the roller bearings.

Close up of outer bearing race with vertical lines/impressions circled.

 

I have also not heard of the different casting numbers.

I believe the reason for the vibration to happen from 80ish mph down to 45ish mph is because the bearings were starting to wear out more over time and mileage. At least we know what caused it now! I think you did the right thing by getting used rear hub assemblies instead of messing around with the assembly/reassembly to measure. Let’s hope someone didn’t leave the shim out of those used ones you’re getting. 🤐 I would get new rear axle locking nuts or maybe Loctite at a minimum!

10+ previous owners is just mind boggling.

 

Agree 100% with the wear acceleration the more I've used it. I did not notice any Locktite Blue on the axle splines, also a clue that whomever did it missed (misplaced?) the shim. Two thousand miles after sitting for years will quickly show what was worn out! I've got the new axle nuts already and just got a shipping alert that the new assemblies should be arriving tomorrow. Yippee!

The car's history is actually quite interesting. First owner (NJ) had it for 4 years and only drove 22k miles. Owner 2 was in PA for one month (!!) and then Owner 3 had it in GA for 2 years and another 16k miles. Owner 4 (also GA) had it for 4 years/30k miles. Owner 5 brought it to Texas in 2010 with 69k on it. It was sold late 2012 and Owner 6 bought an extended warranty with it @76,820. After only a month (again!) it was sold to Owner 7 in Arkansas in 4/13 and it came back to Texas with Owner 8 in late 2013 with 79k miles. Owner 9 got it in 2015 with 82k and kept it in Austin until mid 2017 and 104k miles (tons of service entries during this time period). Owner 10 took it to San Antonio in late 2017 and got it to 109,903 on its last inspection record in 9/17 until I bought it in early 2023 as Owner 11. It had 109,969 and had been sitting for at least 4 years when I got it for the swap project. It had 109,971 when I pulled the drivetrain out.

 

So I installed both new (used) rear hub assemblies today. Not too difficult at all. Marked the pivot bolts, etc and swapping things over was a breeze. The LR hub came from a car with only 87k miles on it per the listing from the seller. Right rear looked quite good as well. The original left side unit did not come apart in pieces like the right side, so I'm glad I started on that one. The left side also had the "normal" XJ8 hub assembly part number on the casting I removed. So, neither side was the XJR-specific part I'd found "should" be there based on the various lookup sites. In any event, the half shaft U-joints were good on both sides, inner and outer, and not bound up/tight so I left them as-is.

Unfortunately, after reassembly, things STILL aren't any better. It does feel that there might be a little less vibration up to 55-60 now, but at highway speeds "something" is still vibrating through the body, from the rear of the car.

After the drive, I put the car as high as I could on jack stands at the back and spent quite a bit of time going over everything again. I found that one of the two bolts I'd loosened on the rear subframe plate to do the rear shocks weren't as tight as it could/should be so I tightened them up and confirmed each of the other subframe bolts was tight. I confirmed there was zero contact with the exhaust to body/suspension anywhere, and that the four exhaust mounting points (subframe and tailpipe) had rubber isolators. I checked and tightened the transmission crossmember and rechecked the u-joints on the driveshaft, despite it being checked out ok two weeks ago. Rear shocks are tight, top four bolts and lowers. They're brand new green Bilstein Sports, with new donuts. No squeaks, knocks, etc anywhere when driving on rough roads, over speed bumps, etc. Parking brake adjustment is good. Rotors and pads have 2k miles on them front and rear, no pulsation or pulling ever. Tires are new Pirelli P7s with 2k miles as well and were just road force balanced (I took rims to shop) last week. I even switched them front to rear today to see if it'd make a difference and it didn't.

I think I need to get someone over here with me to look under the car (well chocked/blocked and on stands) while it's running and in gear to see if anything is visible while running/in gear/at speed. The only challenge with this is that the rear will not have vehicle weight on it while I do this. Not sure if that will be an issue for the better (to find something!) or worse (makes it seem all is good). I'm thinking my next step is going to have to be finding a known good/complete subframe and swapping the whole thing over unless I find something.

Any additional insights from the collective wisdom and experience here?

 

That sucks!!! Did you take apart the used ones and check the bearings and spacers prior to installing them or no?

Just to rule it out, do you have an overdrive button that allows you to turn it off to see if the torque converter may be a problem?