We completed the engine rebuilt of my 2000 XK8 this weekend (the car has 43K miles but the prior owner never changed the oil and sludge caused one of the cam shafts to lock up). The engine started fine and sounds good. But the transmission is now giving us problems. During the first mile of the test drive the information center displayed "Gearbox Fault" and the transmission went into limp home mode (stayed in 4th gear). When I turned the car off and restared the engine, the car ran great for about 10 seconds and then went back into limp home mode.

I will have to pull the codes later this week to determine why the transmission is in limp home mode. However, does anyone have any words of wisdom as to what could be causing the transmission to be in limp home mode and displaying the "Gearbox Fault"? I am assuming this is related to the engine rebulid and that a connector may be bad or unplugged. We did drain the transmission fluid during the rebuild and install a new filter, gasket and fluid. I am wondering if the refill triggered the fault and the electronics just need to be reset, but I am not usually that lucky.

Thanks.

 

I had this and funny enough it was the battery, make sure it is fully charged. You might get lucky

 

We did charge the battery. But thanks for the suggestion.

 

Have you re-checked the trans oil? if you drained it, it just might need a top up

 

Yes we did double check the transmission fluid level after we test drove the car. A little less than a pint of fluid came out of the drain hole when we checked the fluid.

 

what about transmission codes, pull any? A-drum, b-drum damage are pretty common.

 

I too have my money on the battery. I've followed your post and the car has been sitting since spring when you got it. Even though you charged the battery, they can do pretty weird things in these cars. For whatever reason a fully charged battery isn't the same as a new one -- especially since it has sat for a while. Try just swapping one before you buy.

 

Got ur pm kdross. Another member is diagnossing what sounds like a A or B drum issue, but does not get a code with the good scanners. Not resolved yet. Open it up to confirm.

 

This may sound elementary but revisit what things you moved, removed, disconnected and so on even remotely related to the tranny. Look at every connection, reset any cables removed and readjust them if they were disonnected. If the tranny was good before working on the engine, you probably did something to initiate the problem. Be sure the fluid level is correct according to the repair manual, since it has no dipstick. Be sure to pull the codes. You may have drained fluid out of the torque converter which can take a little time to refill and then the level has to be readjusted. Take your time and think methodically as you retrace your steps.

 

h20boy: The transmisison worked fine before the rebuild. So I am assuming oldmots is correct that we did something during the rebuild that the sensors do not like. Hope to pull the codes later this week so we can start pin pointing the problem. I will also install a new battery and see if that works first.

 

Ahhh, sorry...i somehow interpreted the car didnt run and after the engine was repaired you discovered the tranny was limping. Disregard previous post and retrace your steps.

 

h20boy:

The prior owner was able to drive the car to the repair shop without a problem immediately prior to my purchase (he sold the car when he learned he had to rebuild the engine). However, I have no idea how the prior owner was able to drive the car to the repair shop under its own power given the left bank did not work (cam shaft locked up).

 

Please take this with all due respect kdross and simply a question. Did you drive the car and observe that the tranny was shifting well? Again, I'm not sure how that could have been the case if the engine was as bad as you have documented. Did it have the gearbox fault and/or limp message upon arrival to your shop?

 

h20boy:

That is a fair question. I did not drive the car prior to purchase. However, the mechanic did drive the car and said there were no transmission error codes and that the transmission shifted fine. I think we just have to locate a sensor that is causing us a problem. I should have time this weekend to pull the codes and to start hunting for the problem.

 

Crossing my fingers it is an easy find & fix! Will check in later.

 

Good News!!!! We got the car running without any error codes. We drained the transmission fluid and dropped the pan. All of the connections looked good so we replaced the pan and refilled the transmission fluid. To my surprise, the car started fine and drove without the transmission going in limp home mode. Also, there were no error codes. The only problem I seem to have is that the transmission seems to be confused when shifting. However, the more the car is driven the better the transmission gets. I think the car just needs to be driven. It has sat for several years, and we had the battery disconnected for about 6 months. Maybe the transmission needs to "re-learn" shifting patterns and/or it just needs a good long drive to clean out the cobwebs. Regardless, it seems to be driving better with each mile. The car is being detailed today so it should look like new when I get the car tonight. Thanks for all the help and feedback.