Hi All

My recently acquired XJ8 (X308) LWB suffers a mild vibration at about 50MPH which almost goes away at 70, then returns with a vengeance above that (on a private road obviously)

I have had the rear wheels balanced which helped, but it is still there. It feels more like a prop or driveshaft issue to me, perhaps the prop centre bearing? Is there a common fault here to help narrow down my search?

Cheers

Glen.

 

Hi ho Freebird,

My 2000 XJR had similar symptoms... it turned out the inner rims on two wheels were severely dented from some unknown impact (previous owner of course). Being out or round, they vibrated the Jag at 55 + mph. A specialist in truing wheels solved my vibration issue.

 

Yes, I think there's a clue in the fact that the vibration got better when you had the wheels balanced.

One option would be to find someone with a Hunter Roadforce balancer, which actually measures runout with a load applied to the tire/wheel. In the hands of a skilled operator, it will tell you if there is a remaining issue with the wheels or tires. Even if there is no problem, you have eliminated one possibility.

Distorted wheels on cars which are the age of ours, are not uncommon.

 

I've repaired 2 things over the years that caused rear end vibration:

* I had a CV joint on the rt. side half-shaft go bad that caused a rear end vibration (there are 4, 2 on each side). Symptoms were similar to yours until the day it got noisy so I could pinpoint it. Found one trunnion had run dry & the needle bearings failed. It wasn't as simple as pumping grease to check as the joint took grease, but the trunnion that failed was blocked by dried grease, so I couldn't see the issue until the joint was off the car.

* I replaced the torque converter when doing my tranny rebuild. I had a vibration that would start @ 50 mph & smooth out @ 70 (but not always), At times I would also get it @ 35 mph. Found that TC lockup is initiated at 52 mph with full lock up at 57 mph & also when in 4th the TC lock up between 32 and 35 mph. Cause is apparently linked to bad frictions in the TC clutch. The vibration wasn't one I could peg to front or rear. I could feel it through the seat, but it didn't affect the steering wheel, so I was in the same sort of boat it sounds like you are in. The change seemed to fix the problem.

That said, vibration over 50 is usually balance related. As most machines balance to about 60 mph, it could be that you have an issue as suggested above that makes things go pear shaped at higher speeds. Have you tried rotating front to rear to see if the vibration moves with the wheels?

 

The problem is that most machines just balance. A perfectly balanced wheel does not necessarily give a smooth ride. You can have runout but still be balanced. Think about it, a square wheel will balance perfectly.

That's why you should get a Roadforce balance, that actually measures runout, in any case of persistent vibration problems.

 

Thanks for all of the valid advice guys. I will start by swapping wheels front to back I think as this is the easiest option. I can probably judge runout if fitted to the front by using the lock to view the inside as well as the outside of the rims.


I just hope its not the torque converter, though the symptoms to seem very similar!

 

+1 on bent rims and Hunter Road Force Balance.

You can balance a football, but it won't run without vibration.

The Hunter machine, with a good tech using it, found two bent rims on my car and has cured vibration issues that still crop up from time to time.

I have had to return the car multiple times though, each time I have had the tires balanced, requesting that they put a knowledgeable tech on the job.

I bought the "lifetime" balance from my local Goodyear for $25 per wheel and it has paid for itself many times over.

Please read the following info carefully:

Most tire shops don't use the Hunter machine to it's fullest potential and the tech running it must understand that he has to do ALL OF THE PROCEDURES for our cars, including checking run out on each rim, breaking the bead and realigning the tire to the wheel to cure high/low spots and excessive road force.

Our cars are very sensitive to tire/wheel balance issues and they can't be balanced like the tires that are going on Grandpa's Crown Vic.
Vector

 

I am toying with the idea of finding another big luxurious 4 door sedan with a V8 that is reliable and can be repaired by just about anybody: grandpa's Crown Vic or his cousins big *** Mercury beginning to look like the choice.

 

Yeah, Jim, and maybe even a carb. Something without a ECU or fuel injection, or am I back in the 60's at that point?

 

No, no. no carb nor distributor. FI is clearly the way to go. But a 2010 Mercury or Town Car has all the bells and whistles. Then I look out at the green cat and say, "no, no. it is a pretty beast!" Went to Florida (St. Pete) last week -- 1780 miles round trip, mostly open road running slightly north of 75 most of the way (not on 301 between Starke and Waldo!); super smooth and comfortable and 23 mpg round trip. But with badly arthritic knees, getting hard to get out of. I'll post a photo of the royal treatment the valet gave her in Savannah; the rest of the junk went in the underground parking, but not her majesty!

 

Jharts- Keep the cat, get new knees. LOL

 

Bit of a thread drift going on there I think.


anyway, yesterday I swapped the front and rear wheels over and also cleaned up the mating faces of the hub and the wheels to ensure they sat flat and there doesn't seem to be much of an improvement.


I have ordered a second hand propshaft complete with centre bearing off eBay, so will try that next.


Glen.

 

I have similar symptoms and have also swapped wheels that had no effect. I replaced the drive shaft but that was equally ineffective. I have fitted new wheel and hub pivot bearings; no change.
The UJs seem tight and there is only a tiny bit of movement while holding the wheel at 12 and 6.
I now suspect either half shaft is out of balance, or the diff output bearings are worn.
I lifted the back onto stands and applied a few revs. The rear wheels wobbled very badly, but because the vibe travelled through everything on the rear axle so easily, it was not possible to locate the faulty part.

The wheels are now off and tomorrow I will be carefully checking the UJs again but I have no idea how to check the half shafts or output bearings without replacing with known good parts.

 

Hi


I will be following your updates with interest mate. I assume you have you checked the wheel balance? As they are "wobbling very badly" it may be a good plan to repeat your test without the wheels on the car.


I had all 4 of my wheels re-checked for balance and runout by a more reputable company yesterday and the ones that were originally on the rear that I had balanced a week or more ago were in fact pretty poor, runout was OK though. Vibes are now better, but still there.


Good luck with it.


Glen.

 

Yes balance is not the problem but I haven't had runout checked, though I did swap front to rear and made no difference, so I am confidently ruling any wheel problem out.

Today with wheels off I put it in drive and checked the half shafts. There was visible non-perfect spinning on both (right more pronounced than left) and I got a couple of videos of it.
I would expect that when the half shafts spin it should be impossible to tell they are spinning except when looking at the UJs.

http://car.tptc.org.uk:888/right.mp4

http://car.tptc.org.uk:888/left.mp4

 

That doesn't look right to me, you can be pretty sure that you have found the cause of your vibrations there I reckon.


Can you see what might be causing the runout? I will try to do the same test this afternoon.


Cheers


Glen.

 

I can't see - no. However I did notice the stuff at either of the ends seem to be spinning true so I am less suspecting of the output bearings (and hub bearings even though I did replace them not quite a year ago so they 'should' be fine).
I could be wrong but I would assume with faulty output bearings I would notice the joint before the half shaft wouldn't spin smoothly - is that reasonable to assume? I also expect I would be able to feel undue play (apart from the normal acceptable) while moving the wheel in and out.

I did have a thought about the half shafts. The cross section doesn't have to be absolutely circular for it to be balanced. It could have a couple of slight flats on either side and spin perfectly balanced but it would exhibit the apparent out of true behaviour I have seen. In this case though I don't suspect that is what is happening (because I can't see any such flats and the shafts feel circular all the way round).


I have a couple of pictures here of leaks around the diff outputs. Do these help to reinforce or dismiss any causes? Even if these leaks are 'nothing to worry about' (I doubt it) how can I fix them?

http://car.tptc.org.uk:888/diffoutR.jpg
http://car.tptc.org.uk:888/diffoutL.jpg

 

Hi


Unfortunately I spent all weekend looking for a Mini for my Daughter so had no time to repeat you test on my car. Fine balancing the wheels has reduced the vibes to an almost acceptable level - but it still annoys me a lot. At 70 it's fine.


I would agree that if the area behind the UJs are running true that the bearings each end are probably OK.


It's also true that the shaft doesn't have to be round to be in balance, it could be square or even triangular, but we know it's supposed to be round.


So, for the shaft to run out with respect to the bits the other side of the UJs, then it would seem that the UJs themselves are offset somehow.


I am speaking as a total Jag novice, but I would have thought that as the shaft/UJ assembly is also the top "wishbone" it's under either tension or compression from the spring so it will be difficult to feel for wear in the UJs without removing the spring first.


As an aforementioned novice, I can't help with your oil leak question either I'm afraid - best to post a separate thread I think.


Where in the UK are you?


Glen.

 

Sometimes it's worth sharing one's thoughts to get someone else to come in from a fresh perspective, and your comment about the UJs being offset therefore causing the 'wobbly' half shafts sounds so likely that it is going to be my main concern for now, even though I did previously rule out the UJs.

It also didn't cross my mind about the load on the UJs making it difficult to detect problems, but I do understand the half shaft wishbone thing and I'm annoyed I didn't realise myself sooner.

I can't be bothered to release the spring tensions, and I haven't changed the UJs in all the time (nearly four years) I have had the car so I do think I could probably change them to be on the safe side. It will cost a bit over £100 for all the bits including the use-once hub nuts.

I'm in Worksop, quite a way from Merstham.

 

You are more than welcome mate. I mentioned it as I had a similar problem with my Triumph Vitesse propshaft UJ causing the shaft to runout and vibrate.


Much easier to fix on one of those though.