STATS: 2002 X-Type Jag 94k miles 3.0 engine. REPAIRS EFFECTED: Changed the transmission fluid in 3 efforts as per instructions found on this forum, changed upstream oxygen sensor after getting a 1647 code as per noted instructions found on this forum, changed oil with Castrol Oil and Bosch filter as per instructions found on this forum. THE PROBLEM: Engine shifts to neutral when rapidly accelerating. I have no error codes, but if you experience this problem several times in a row you get a general gear box failure message but it never goes into safe mode. When the car goes to neutral and you remove foot from accelerator it re-engages without noise, jerk, or sensation of any kind except you regain power. When using the sport mode you can down shift successfully without any problems and it shifts up through the gears very well until you attempt to kick it into rapid acceleration. Then, the transmission just floats you to neutral, you gain rapid rpms and the condition rights itself when you allow the rpm's to fall back. Otherwise the transmission shifts and responds flawlessly. This condition has persisted for around 2000 miles of driving. It hasn't gotten worse nor better. When I changed the O2 sensor it greatly improved but is still present. Love this car or I'd kick it to the curb. Could the problem be in the Transmission Control Unit or the main computer? I'm pretty lost at this point. I've read everything I could find here and seen some similar reports but with no conclusion. Suggestions would be helpful. Reading posts here have been very helpful, but the darn problem still persists. thanks

 

I was thinking "torque convertor" to start with, but usually they fail by locking up, not spinning free.

If you have a burnt-out clutch package - a "soft-parts" failure - that might well explain why it starts spinning free under load (acceleration).

Transmission fluid changes are always a good idea, but they won't solve that problem.

One thing that could help, however, is to pour some (get ready to holler, you purists!) "Transmission Doctor" kind of juice in there - like a Justice Brothers (JB), Lucas or other "quality" product. It will swell the clutch plate material and seals up a bit, and that may well remedy the problem for a while.

Nothing to lose at this point, might be worth the try.



Better living through chemistry.

 

I've used the Lucas product before on a couple of 60's cars. It might do some good but I'm hoping to find a permanent solution. I might add info here: I notice that the "neutral condition" manifests itself at about 2,000 rpms when driving in standard mode. In "sports mode" the first three shifts are already above 2,000 rpms and so it doesn't happen until after the third shift. Maybe that sheds some more light onto the problem. I've never experienced anything like it and appreciate all the imput I can get.

 

I followed the additive suggestion Bruce since I have had some degree of success with the Lucas products on my 60's cars. I don't think it can hurt, but how much it will help this situation we'll just have to wait and see. I figure we should see some change in a week, so I'll get back if I get any improvement or not. Like you said, what do we have to loose. I only had the one suggestion so I'll embrace it and hope for the best. Thanks Bruce *crosses fingers** Have a great day!

 

Did it do this before the fluid change?

 

Yes, we drove the car for about 3 months / 3000 miles before this float to neutral thing started. Then read on here about someone else with similar problem and followed the instructions for changing fluids in the transmission which was accomplished without difficulty. However, we experienced no improvement. We continue to drive the jag but its getting no better nor any worse. So long as you don't ask it to rapidly accelerate there is no problem, and when you do need her to go faster you just have to do it a bit more gradually. Your concern or suggestion might be?

 

If it started after the change, I'd figure some crud moved from some inaccessible crevice out to the kickdown flow.


The JF506E box uses solenoids for gear changes, including the kickdown.


First thing I'd suggest is having the transmission computer read, and perhaps reset; it may just be a programming glitch.


Otherwise, it may be time for a valve-body cleanup and a new solenoid 'pack' although the transmission uses separate solenoids and not an actual pack.

 

I will schedule a check and re-set of the TCU as soon as possible. It has been my suspicion that it is computer related. The shifting of the transmission is just too flawless for me to easily believe it is mechanical. The transmission just act so so solid in every other aspect. I'll get the check and reset accomplished and report the results back. Thanks for your input and for following my threads.