XJR X308 issues

[jcuthell]

So I finally did end up buying an XJR. I paid £3400 for a 98 S with 75k miles with a private plate on. It was described as excellent – it wasn’t really but we spent two days on it repairing bumpers, painting mirrors etc and generally improving things. All was good but I have now notice significant vibrations through the car on the motorway. It vibrates through the wheel and seat but I am not sure it’s a suspension related. At lower speeds it doesn’t seem apparent but between 50 and 70 its significant but again not always there. Any ideas where to start isolating the problem?

It also periodically has a rear brake warning and is hard to move from Park to reverse or through the gearbox.

Thanks,

James.

[prand]

jcuthell said:

So I finally did end up buying an XJR. I paid £3400 for a 98 S with 75k miles with a private plate on. It was described as excellent – it wasn’t really but we spent two days on it repairing bumpers, painting mirrors etc and generally improving things. All was good but I have now notice significant vibrations through the car on the motorway. It vibrates through the wheel and seat but I am not sure it’s a suspension related. At lower speeds it doesn’t seem apparent but between 50 and 70 its significant but again not always there. Any ideas where to start isolating the problem?

It also periodically has a rear brake warning and is hard to move from Park to reverse or through the gearbox.

Thanks,

James.

I've got similar wobble with my recently bought '97 xj8, it seems that it's common on these cars between 50-70mph. My tyres are shockingly old and worn so I'm starting there with replacements, balancing, tracking etc and fingers crossed this solves the issue (in fact I've had this with other cars too, where new tyres and balancing have solved an awful ride). A wheel itself may be bent? So worth checking too.

As for the other problems - Jaguar Steve has left his very helpful and comprehensive x308 buying guide around on several threads in here, and he makes a major point around gearbox issues. What you are describing does not sound like great news as I believe it shows the auto box is on its way out, and there's lots of info about the "correct" way of changing oil in the box to keep it running in tip top shape, if this has not happened, then its again, not good news.

I'm a bit concerned with my car as it does sometimes need a think to move from D to R and back again, it has supposedly had a "reconditioned" engine recently fitted with new oil & filters, but I don't think it was a great job as I've also had some trouble with the selector sensors. I'll see what happens over time if this issue gets worse and hope for the best!

Hope this helps.

[Jaguar steve]

A X308 can vibrate quite badly with the same amount of wheel and tyre imbalance or out of true that you'd hardly notice on other cars. It's worse still if you have two or more tyres that are out of true or have variations in carcass rigidity (thanks Vredestein ya b'stards) around the circumference as depending on the relative tyre positions you'll get constructive and destructive interference patterns of vibration that will sometimes make the car smooth as silk and others have it shaking like a stting dog for no apparent reason at all.

You need to bear in mind too most tyre fitters don't give a toss and most balance machines are calibrated... No, calibrated isn't the right word. Set roughly to around 10g tolerances and any rough or gorilla heavy handed slamming the wheel onto the cone of the balancing machine can disturb it's accuracy and repeatability further.

What you may need to do is Google Balancemycar and find a tyre fitter with a Hunter Roadfore balancing machine. This bit of kit used correctly will identify any variations in wheel circumference or true and also locate any high or weak spot in the tyre. It radially matches the two together by running the tyre against a heavy roller whilst monitoring the deflection to give the lowest possible variation in real world roadforce and when that's established finishes off with a precision balance. The fitter can then place the set of wheels in the optimum position on the car starting with the best one on the offside front and worse one on the nearside rear. It's a lot of faffing about which takes time and costs money and you may end up binning what look like perfectly good tyres but it works a treat for problem cars.

Gearchange quality is not the same as gear selection quality. If the J gate is stiff or sloppy all you may need to do is replace external gearbox parts like the J gate assembly or cable. A tiny and consistent delay in actually engaging drive or reverse after gear selection is normal, variations in time or coarseness are not.

Edited by Jaguar steve on Thursday 16th June 05:24

[jcuthell]

Sorry for the delay my 10 week old son is keeping me busy.

So I left the car at work overnight in a cold garage and was suprise that the tyre pressures are 32 to 34 psi. I think I am right in saying they should be about 26psi? I am going to reset these. Certainly when I drove it 150 miles home on collection there was no vibration so it seems a bit strange it has come on so soon.

In terms of the gearbox I don't think I was clear enough. Gear changes are quite smooth especially once the engine is warm. What is difficult is moving the lever from drive on start up. With foot on the brake it takes several attempts for the lock on the gear selector to be removed. I hadn't driven it for two weeks but it doesn't always happen.

Cheers,

James.

[Jaguar steve]

jcuthell said:

Sorry for the delay my 10 week old son is keeping me busy.

So I left the car at work overnight in a cold garage and was suprise that the tyre pressures are 32 to 34 psi. I think I am right in saying they should be about 26psi? I am going to reset these. Certainly when I drove it 150 miles home on collection there was no vibration so it seems a bit strange it has come on so soon.

In terms of the gearbox I don't think I was clear enough. Gear changes are quite smooth especially once the engine is warm. What is difficult is moving the lever from drive on start up. With foot on the brake it takes several attempts for the lock on the gear selector to be removed. I hadn't driven it for two weeks but it doesn't always happen.

Cheers,

James.

You need an accurate and repeatable tyre pressure gauge with an XJ. There should be a label under the centre console lid giving the XJ8 recommended pressures for all the variants of wheels and tyres fitted. There will be two settings, Comfort and High Speed. For the record and obviously read cold they are (for 225/60/16 tyres anyway) Comfort 26F and 28R and High Speed 32F 34R so what you found seems in the region of right. Pressure will increase with temperature and I always notice a subtle hardening of ride after 10 miles or so on my car. If you don't have this info tell me what size tyres and wheels you have and I'll have a look.

If the transmission selector jams in Park then have a listen for a distinct click from the centre console when you press the brake pedal with the ignition on. There are actually two microswitches inside the brake light switch assembly, operating the brake lights and cruise control and J gate lock and if the J gate lock one is not always making a clean contact this is a likely cause of the problem and a shot of WD40 right into the switch is whats needed first. You can unscrew the hex plug on the front left of the J gate console, poke a pen or thin rod into it and very gently ease the selector manually from P at the same time if it's really jammed or you have total electrical failure.

I think the same applies to the lock preventing shifting into D or R without the footbrake on but never had to look into this so may be wrong as there is a another switch in the gearbox that may control this or some of this function instead. No harm in trying a shot of WD on the brake switch 'tho.


ETA. You have a 10 week old and an XJR? Too close to call which is gonna cost you more...

Edited by Jaguar steve on Thursday 16th June 12:02

[jcuthell]

Annoyingly I left the keys at home so haven't got the manual but the tyres are 255/40 18 inch wheel.

Thanks James

[Jaguar steve]

Comfort 26F 28R. High Speed 32F 34R.

[jcuthell]

Thanks.

What I didn't mention was that Joel was born just one week before the XJR turned up! Wife not impressed with purchase...