This has happened twice within the last week. There's an area near my office where the speed limit is 25mph. Usually, when I keep at this constant speed, the transmission would upshift and the rpm would rest near 1500 or so. But on two occasions, the rev rose to rapidly to 3000-4000 rpm and would not upshift (it felt I was kept in first or second gear). I left off the throttle quickly to let the rpm drop and when I got back on the throttle, it raced again right up to the same 3000-4000 rpm point. This quirk stopped after I come to a red light or stop sign and re-accelerated the car.

I suspect this may be related to another incident which occur the same week. I was stuck in slow moving traffic and I was getting the high revs again, which then disappear after I come to a complete stop and re-accelerate. After the traffic picked up, I was accelerating to about 50mph, I felt the car chug forward and stabilize, chug forward and stabilize. I looked at the tach and the needle was going up and down between 2000 and 2500 rpm quickly like it was upshifting then downshifting then upshifting then downshifting. This went on for about five seconds. Under the speedo, I got the message, "High Gearbox Temperature". (I've read a few "Gearbox Fault" threads on the forum, but never encountered a "High Gearbox Temperature" thread).

When I first got the high revs, I thought perhaps it was "S" button, which wasn't on. I pressed it on and off but that didn't appear to fix it. Then pressed the cruise control button on and off. That didn't work either. I decided to shift the car, but then realized, no, that WOULD raise the revs, so I stopped doing that, too.

Has anyone ever had a "High Gearbox Temperature" message or had a similar experience? I suspect I'll be taking this to the dealer, at least for a diagnosis.

 

Here's an update and fix for my XK8's transmission misbehavior.

Took the car to the dealer and found the following:

Code P0711 appeared. To confirm the diagnosis, the mechanic cleared the code and test drove the car. The code reappeared. Fault was traced to the transmission's internal wiring harness.

The wiring harness was replaced, car was re-test drove, and the code did not reappear. I've been driving the car for the last three days and so far, no more wacky transmission.

 

Thanks for the followup information!

 

montauke,
What year is your car? And if you don't mind me asking, how much were the repairs?

 

I have a 2002 XK8, with about 69k miles.

Replacing the internal wiring harness came up to a bit over $650 (including tax and the environmental charge). That includes:
- $360 for three hours of labor
- $200 for the harness (LNC3380AA)
- $16 for the retaining clip (JLM20213)
- $10 for two o-rings (JLM20212)
- $32 for the gasket sump (JLM20204)

 

Thanks. I had my '01 (mileage, 42k) in a while ago and was told the harness was on the way out and it would be around $900. I haven't done anything about it yet because there have been no symptoms. But i was curious if the price was good or not.

 

the misbehaving transmission started out once or twice a week, then at least once a day, then pretty prevalent. The deterioration all happen within a span of a month. It may be good to replace the harness sooner than later as I have been stuck a few times before the problem fixed itself to where I could get on the road again.

 

Wow, that could have been alot worse montauke. I think brutal has mentioned this harness in other tranny threads as well.

 

I just received this "High Gearbox Temp" message this morning. I have a 98 XJ8 with over 100K miles. What harness or part specifically goes out? Any info would be appreciated.

Thanks.

JP

 

Scroll up. Montauke spelled it all out! Check out Car Quest to see if any of those parts are available thru World Parts.

That is if are trying to do this yourself.

 

I am...thanks...didnt even realize he had part numbers listed.

 

...and all is well in this thread, once again.

 

I've just got the same High Dearbox temp message on my XJ8 3,2 sovereign 2000 with 100000km. do you know how difficult it is to change this harness ? do you know how long the harness is and with how many connectors ?

 

not a clue, sorry. You've got the part number, I suppose you could call a parts house and ask.

 

The harness under discussion is within the transmission oil pan and extends only to an external connector. Requires draining/refilling transmission which is really not a big deal.

 

I got the same message on my car a few times. I changed the transfluid and the issue went away. It has never came back sense.

 

thanks for the contribution CJRM! Glad you found an easy repair.

 

Thanks CJRM, i'll look at this plug ASAP. could you tell me where it is located ?

 

Left rear of the transmission, just above the oil pan.