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ANDY ! this post is 10 months or so old and will not open for me...would you be able to post it again?... I am trying to learn all possible before finding the right shop to open my ZF6HP26.... I thank you ALL for being active and helpful to my new community of enthusiasts; a tremendous help to me already !
It's the same as the one in post #19, that one works.
Let me explain my recent experience with LED brake light. After changing my regular brake light for LED, I found my 2006 XK8 sending a Dashboard message For check brake light. I didn’t install the resistance at that time so I said, I will just clear the message.
On weekends i went for a nice road trip and and found the beautiful Jaguar electrical nightmare! My transmission was not sifting At all while on D when leaving the stop sign. I had to shift manually or remove the Sport mode, then move up until 3000 rpm, lift the throttle pedal then it work.
Cruise control was not working either. So next morning I tought that all this happens after putting 2 LED brake light so I put back the regular 7258 bulb in place.
I went for a road test and suddenly everything was back in perfect condition. The gearbox was working as it is suppose even on Sport mode, Cruise control was working perfectly and the dashboard message was gone. So Jaguar is a very sensitive CAT to any electrical fault.
So be careful if you want to use LED bulb, you could find yourself with others issues that you had never planned.
Very interesting!. Clearly, the tinkering you did with new LED brake lights made the Transmission think vehicle was braking. The Transmission Control Module is fed status (Via CAN BUS) regarding the braking condition and will not enable ratio change-up if the brake lights are on. This is irrespective of engine revs and whether you are actually braking or not. So the brake light circuit is key.
As you know, when you depress brake, the pedal switch turns on the brake lights, but also, the system is looking for volt drop to check bulb health. It was this closed circuit that was somehow being fooled and affecting your Transmission operation!
In standard brake light set-up, the system is fail-safe with no affect to gearbox – but there’s one exception to be aware of in future. The brake pedal switch has a little built-in ratchet that can require resetting if the brake pedal has been pulled hard towards the seat, the ratchet will set and the brake lights come on permanently without the pedal being depressed. This situation will also cause the gearbox to not change-up in D-Drive (like your failure mode). So, if same Gearbox fault ever happens again, one check is to see if the brake lights are staying on all the time....
This is what happened to my 05 XK8 with 49,000 kms. Transmission wouldnt shift up most times and if it did into 2 it was at 5000 or a flick of the gas would also shift. I also had failure message of cruise unavailable and a rear light issue. When the ratchet is out of place the car thinks and acts like your foot is on the brake pedal. I was lucky and could at least drive the car but with mine the ratchet was just done and required a new switch where after all worked perfect. I did try a switch from a wrecker which was also faulty so be careful as the effects of the switch will appear to have a fried transmission so some people will just part out the car if it has high mileage. Best to go new with the switch,
I had not been here in a few years I do not believe, so most likely posting in the wrong place. With that my 2000 XK8 had a delayed engagement from park to drive and drive to reverse and again from a stop light to going. Not real bad but not right. NO codes!! Took the transmission out. Second time now...First was to replace rear main seal. Anyways I thought I needed clutch drum A. They are known to crack and trash your transmission. Turned out the valve body had a crack in it. Just thought I would pass the info on. This is on the top side of the valve body. You have to remove the filter and valve body to check it for cracks. I saw this same crack happen before, so some what common. Normally clutch drum A's upper cage comes apart trashing the trans. They make a more heavy duty one...
12-28-2019, 02:15 PM
