Hi guys.
I am new to XK8s but am looking at a 2002 Xk8.
The car is in good condition, but on my test drive there was a heavy clunk as the car changed down from 5th to 4th under gentle deceleration from about 70mph.
All other gear changes were smooth, but the fault was repeatable with the same manoeuvre. There did not seem to be an issue if the car was accelerated and decelerated hard, but it repeated on gentle deceleration. There were no warning lights and otherwise the car drive fine. This is a well maintained car which is only used occasionally. It has done 80,000 miles. Has anyone got any advice on this?
Many thanks Mike

 

Can anyone give me some advice on what goes wrong on the 5 speed auto box and typical mileage for this?

 

Hi Mike.

Others more knowledgeable about auto trans may recognise the symptoms, but with 80K under its belt, worst case scenario is that the transmission is failing, and you must take that into account if you are considering a purchase.

If it's cheap enough, and you're happy to entertain the possibility of a trans rebuild, then OK. Otherwise I'd pass.


Just my

Mike

 

I had the famous "sqwak" and rough shifting. Replaced the fluid and pan and seems both have been resolved. Yours may be a different issue. Mine has 62000 mi. Common wisdom appears to be replace fluid after 60000mi.

 

I would say the same thing. If you are willing to deal with the hassle of pulling the transmission off the car (worst case), and the car starts cheap enough, then go for it. As a general statement, these older cars are best suited for the home-mechanics type, so to speak. Having these cars maintained by pros gets expensive very quickly.

For information, the earlier XK8 have a 5HP24 made by ZF. There are plenty of rebuild kit of various depth and a lot of information around. That trans was used on a lot of cars throughout the years. You could start with a flush and refill, and go from there. The major problem for XK8s on early transmissions is the "A Drum" failure, but I believe the symptoms are different.

Another approach is to visit a dealer type shop an get the codes scanned. Maybe there is some more information to be had there, and with a code you can search for specifics.

Chances are that it is something other than the trans itself. The switch on the side of the trans can be a problem. Also, it is entirely possible that there are other issues in the driveline, like the rubber coupling with the driveshaft, loose bearings on the differential or even neglected half shaft U-joints. My understanding is that the rear sub-frame mounts can also be worn and require replacement. What about engine mounts? I assume a conventional shop could put the car on a lift and figure this out, no need for complicated Jaguar-specific knowledge there.

Best of luck, keep us posted.

PS: Don't forget to ask about the secondary tensioners...

 

That's great advice. Thanks for taking the time.

 

The car is back at a Jaguar specialist who has agreed to get some codes off the gearbox, although I did not get any engine warning lights on my test drive.
Prior to the test drive I had paid the Jaguar specialist to survey the car so I would hope that he would have highlighted any worn mounts or bushes.
I have also spoken to a gearbox specialist who advised that if it is a sticking solenoid valve that this should not be sticking due to lack of use, but is likely to have debris/sludge in the valve from the clutch pack and the problem is likely to get worse and not better.
His advice was also a fluid and filter change. Any further thoughts in this? Gearbox otherwise as sweet as a nut.

 

Most likely no codes will emerge, based on experience of other posts here on same sort of symptoms. Anyway with 80,000 miles, change of ownership and unspecified detail of service history, IMHO, I would recommend a full pan, sleeve and fluid change. Kit is modestly priced. ATF is expensive, but type & spec is critical. Even more critical is the temperature sensitive filling process. Perhaps your indie will quote you?

Best wishes,

Ken

 

Hi Mike,
Hope I didn't scare you too much, but you need to be 'eyes wide open'.

It doesn't sound like the all-too-common 'A' drum failure as fmertz noted, and it could indeed be slop in the drive line somewhere. Odd that the specialist didn't pick up on it, though.

Fully agree with the others on the filter/fluid change.

Good luck,
Mike

 

Hi Guys thanks for the reassurance. The owner has shown me a receipt from the gearbox fluid change at 60,000 miles in 2012, which he assures me was done as a precaution. All other service records are spot on. Whilst I could live with a fluid change I am not sure we would want to face a full gearbox rebuild - locally quoted at £3000.
Other than the clunk the gearbox feels and sound fine.
Can anyone give me typical life of a 5 speed zf box before a rebuild is needed?
Also are there other failure symptoms I can look out for if I return to do a second test drive?

 

The 5HP24 is not known for its great reliability. MANY have come to this forum for help. The more common issue is the A-drum failure, which requires a mechanical rebuild. To push that possibility back, folks install the Transgo valve. It reputedly lessen the pressure on the A drum in question.

Transmission is 3 parts: Ancillaries (like shifter, speed sensor, etc), valve body and mechanicals. It only gets truly expensive if you need to rebuild the mechanicals because the trans needs to come off the car. The way you find out is you pull the pan off the bottom of the trans, and inspect the magnets for metal shavings. Shavings means mechanical damage and an expensive rebuild.

The other problem can be the valve body. The good part is that it comes off the bottom, no need to pull the trans off the car. Here, same as ancillaries, it is typically driven by the codes (Jaguar-specific, not OBDII).

The fundamental problem with these expensive trans is that when you seek advice from professional, it always seem to go in the direction of an expensive replacement, not this one cheaper thing that happens to be the root cause...

 

Hi Mike - many thanks it is better to have knowledge to help you make and informed decision. I am in the lucky position of not having bought the car yet. I could have easily missed this fault had I not taken a run down the A3 as part of my test drive. I still like the car and hope to come to an amicable arrangement with the current owner if the fault is not too serious. Will wait and see what the specialist says.

 

Dear Fmertz - thanks again for some excellent advice. I have now read the jaguar explanation on how this gearbox works along with a number of other useful texts.
Mike

 

Hi,
my XK8 does the same thing,a rough shift from 5th to fourth gir. Occasionally it will light up the check engine light and a Transmission failure error in the Central display, but not always.
My code Reader indicates a problem with the Torque converter clutch circuit being stuck on is causing this.
The car is going in to be fixed soon, but my mechanic is confident this is the solenoid that is having a problem and the fix is not expensive (raltively speaking). This is based on the fact that my car had a gearbox overhaul and New torque converter installed 6 months before I took ownership.
It also had the wiring harness for the transmission replaced at the same time.

A scan with a code reader will reveal if this is the case with the car you are looking at. Could be a barganing point

 

Hi Doogledee that is great information.
Let me know how the repair goes.
Many thanks
Mike

 

I'm pretty sure I am right on this. The shift from 4th to 5th or visa versa is not a gear shift. That is a locking or unlocking of the torque converter. I can just feel it on both my XK8 and the X300. In that case I believe a good servicing of the transmission , change fluid and filter would make for a smoother locking and unlocking of the torque converter.

 

Will do, It goes in on the 29th of May

 

I havent heard anything yet from my garage, but the car is with them and hopefully it will be ready today.

 

Hi Ezdriver
I have found quite a good description of the operation on the 5HP24 gearbox on the forum and from what I can tell the torque converter is locked up once you get out of first gear. All other gear changes happen by progressively locking up one clutch and releasing another, so timing is critical to achieving a smooth gear change. The heavy clunk on our gearbox has reduced in magnitude with use, and now only happens intermittently. I have now covered 300+ miles in the car at motorway speeds without any significant clunking. From the service history I note that the gearbox oil and filter were changed 10,000 miles ago, so I am hopeful that we won't need major repairs in the near future.
Thanks to everyone for your advice.