Hi group this is my first post
I have a 2002 xk8 automatic 4.2 V8 with 99000 miles
my problem is when I accelerate from a stop position sometimes the gears wont change and stick and obviously the revs go right up to 4000-5000 then if I hit the accelerator to speed off it clears and changes as normal
it don't do it all the time
Do I have major problems or is it something simple

 

I'm not clear on exactly the problem. Are you saying that if you step on the accelerator all the way, it never will up shift? I will say that in sport mode, when I floor the gas pedal, it will rev up to near redline, but will shift.

Anyhow, the 6hp26 is a pretty robust transmission and I haven't heard of such An issue. Shift points are controlled by the TCU, with inputs from the ECU and other sensors internal and external, but always electronically controlled. The TCU is adaptive, and the adaptations have been known to drift, but again, I neaver heard of this. I would first have the filter and fluid replaced and at the same time have the TCU reflashed and adaptations reset (happens with the reflash regardless). The fluid is a good preventive measure, and can make an improvement in shift quality. The reflash has made improvements for many members. During the reflash process (prior actually) any TCU fault codes will be read, which might yield info. This is where I would start. BTW, are you sure the gear selector is in D?

 

Have your shifter cable adjustment checked first.

Gus
www.jagrepair.com

 

Hi there
thanks for the response
Basically when you accelerate at a slow steady pace the gears don't change they stick in high gear but if you put your foot down as if to accelerate a bit quicker there is no problem at all it just changes straight away as normal

 

I don't have an answer for you but am interested in the issue. Just having trouble understanding your description.

"accelerate at a slow steady pace the gears don't change they stick in high gear "

Do your mean the car starts off in a " high" gear, say 6 th? With sluggish acceralition?
Or do you mean the engine revs up to a high RPM and the transmission will not shift?

"put your foot down as if to accelerate a bit quicker there is no problem at all it just changes straight away as normal"

Do you mean the car " kicks down a gear" to accelerate quicker?
Or it up shifts to the next gear?

EDIT: never mind I just reread your first post and understand now.

 

Sorry my mistake, it sticks in low gear and the revs gradually go up and your waiting for the gear to automatically change as normal but it doesn't, but when you take your foot off the accelerator and put back down again with a bit more urgency it changes straight away to the next gear no problem at all.

 

I didn't realise the 2002 got the 6HP26, if it did.

Check shifter cable, especially at trans side for loose/missing bolts.

 

To test put the shifter in the manual shift mode in position #5 and see if you experiance the same shifting problem.

 

Thanks for all your posts, i think I may have solved this problem with the help of my mate.
A few weeks ago I had a warning message saying check rear lights / cruise control unavailable this turned out to be the break light switch above the break pedal which I had changed straight away at my local specialist as I no it can be a tricky job.
Last week which was the last time drove the car I had a guy stop me to tell me that my rear break lights were all sticking on so I arranged to book my car back in to have this new break switch checked to see if it was sticking or faulty. as I took the car to the garage this morning I had my mate follow me to see if my break lights were still sticking on and by pure luck we noticed everytime the lights stuck on was the time were my gears wouldn't shift up on acceleration, so we had the break light switch looked at cleaned and put back in. since then my break lights have been working fine and I have no gear shift troubles at all, what I will do is use the car over the weekend to make sure its not just a coincidence and post to let you no if I am successful
Could it really be that simple or a coincidence I have my fingers crossed, what do you think is the break light switch tied in with the transmission for some kind of failsafe?

 

Sounds like what happened to me. My one is all fine now.

https://www.jaguarforums.com/forum/x...-start-104137/

Happy cheap fix - compared to a new transmission.

 

im pleased to say that I found that it was the Brake light switch behind the break pedal it must be tied in with the failsafe system thanks to all for your comments and help

 

well tks guys , your posts have solved my query as I have just been experiencing the gear shift problem & this just after having a cruise not avail/check rear lights warning. This little momma seems to be the cause of lots of peripheral problems so I will now change it cheers Mike

 

continuing on with this quite common fault, I have ordered a new switch but thinking through the system it is known that to operate this switch is activated when the brake pedal is not depressed. If you listen carefully you can hear the switch clicking "off" when pedal is depressed. with this in mind I tried to adjust the pedal /switch to ensure a better contact as no doubt with wear the pedal may not do this. As it happens when I drove the car it all worked normally ( I did help by putting my foot behind pedal at first). I did at one stage get a "check rear lights " warning ( cannot get rid of this until recycle) so I will change the switch but this may help others who may not need to .cheers Mike