"gearbox fault" ,mode "amber"

[mike020150]

The Merc box fitted to the 4.0 litre XKRs does have a known mechanical weakness but not normally at such a low mileage. The good news is that, unlike the ZF box in the naturally aspirated cars, it's usually repairable. However, before jumping to expensive conclusions I'd open your Christmas present early or get some good diagnostic advice. Mike.

[cjrm1]

I did open my present early and the code was P0730, incorrect gear ratio, car went into mechanical limp home mode.
I took the car out again and the fault did not repeat with the car driving normally. One cause mentioned was low gearbox fluid, I plan to get this checked out as a precaution anyway.

[mike020150]

How did things progress? Was it low fluid or more serious? Mike.

[cjrm1]

Have used the car several times now without any issue. The fault code has disappeared. There are no clunks or other worrying mechanical sounds, when I floor it, the car takes off like a rocket.
I spoke to my local Jag specialist who said that the most likely reason was a computer glitch/isolated problem and that there should be no reason to be concerned.

[mike020150]

I'd be tempted to clean the connectors in the gearbox loom with switch cleaner. If a poor contact was the cause of the original fault it might just save you another anxious moment and a frustrating journey home in limp home mode. These faults always seem to happen when you're in a hurry or at some other equally inconvenient time. Mike.

[alanb]

I have an XK8 01MY, 39k miles. Twice in the last few days I have had this message flash up, both times only 4-5 miles after starting. On both occasions I have pulled over, stopped the engine and re-started. The warning does not re-appear and the car drives perfectly with no sign of anything wrong.
It looks like a malfunction in the circuit buit does anyone know if it could be something more sinister and expensive !)
Alan

[mike020150]

Alan, There's no knowing if or when these messages are crying wolf, especially if there's no sign of leaking transmission fluid. Find a Jaguar specialist or dealer with Autologic or Jaguar diagnostic equipment and get the car checked. The peace of mind alone will be worth the cost. Mike.

[scallan1956]

Hi Peter, I have the same problem on 1998 XK8 105K miles, took it in to my local independent auto box centre, no fault codes registered on autologik system. they had this same fault on two other XK8s of similar milage, only way to cure this fault is to remove gearbox and full
stripdown and recondition (Gulp). they have quoted me £1650 + vat
for the complete re- build incl parts and Oils. Funny thing is I already had the filter/gasket/o ring, to have the oil changed. Also 12months or 12000 miles Guarantee. Already done the timming chains guides and tensioners last year. hopfully not much more to go wrong now, rear differential maybe . I hope this will be of help to other members on this forum.
Looking forward to Easter now. I will have the car back by then, oh joy
long weekend of driving, hopefully I will let you all know how I get on.

[cjrm1]

An update on my story.

The warning light "high gearbox temp" came on more regularly, but still intermittently with no consistency at all.
My main dealer suggested changing the valve body for £1,700.
I took my car to David Marks, who fixed it, by replacing the just the valve block, which is mounted on the body and contains the sensors etc. He found the connector plug was full of water, which had probably caused a short in the loom, the connectors on the Valve block were also pitted.

So far no repeat of this problem at all and fixed at a fraction of the main dealer quote