While driving home after a short twenty-four mile trip, and after climbing a mountain, the message "high gearbox temperature" appeared in the message window. The message disappeared and then reappeared and then disappeared. There were no codes or further messages. The transmission did not downshift and I drove slowly home and put the car in the garage. It's a 2000 XJ8L with 130,000 miles. I have owned the car for two years and it has never given any trouble before. Is this something as simple as transmission fluid or is this a trip to the dealer? Where should I look first?

 

this sounds silly, how big an incline and for how long did you drive the mountain? fluid levels are pretty critical, so it might be as simple as a half quart top up required.
But, having the ZF transmission, it could be something more serious, although fixable, like drum failure. I'm not aware of the symptoms these trans show when they fail, but someone with experience will chime in.
Servicing the gearbox is not a simple process, search in the sticky section in the XK8/R forum before you attempt a full fluid change, topping up should be first.
Look here for any shared issue, re the gearbox not downshifting.
https://www.jaguarforums.com/forum/s...earchid=794762

 

Obviously this kind of thing needs to be looked into.

Did you notice if the water temperature was high?
Has anything been done to the transmission? -- have you noticed any leaks?
Was it slipping?

For a start -- you will have to make sure it is correctly filled and what is the status of the fluid.

 

Didn't notice any gauges reading out of the ordinary. Nothing done to transmission nor indication of leaks on garage floor. Mountain is 2000'; climb from 900' to 1800'. Drive up and down the mountain every day and it takes about 6 minutes. Transmission did not slip; just no downshift.

 

So you are saying that that the transmission stayed in top gear -- even when you came to a stop?

 

When incident occurred initially, car stayed in low gear, even when it came to stop, which was expected. Car did not upshift as expected when moving.

Waited an hour or so 'til car had cooled. Car started with no messages on message screen. Drove car about eight miles. Everything normal. Shifted as expected. It was as if nothing had happened. Checked gauges while driving -- nothing abnormal. Double checked garage floor to see if there was leakage. None found.

It was as if nothing had happened. Gremlins at work?

Will put on rack and check fluid level tomorrow AM.

 

I just had the same message while driving tonight; up a hill- car drove fine. I had a full transmission rebuild less than 1,000 miles ago. So back to the trans shop - good thing he gave 2 years 50k warranty on tras

 

There is a TFT sensor that is integral to the internal trans harness, and they do go bad from time to time.