113K miles, did a 7 qt mercron sp change last month...have driven @ 800 miles and other than a slight surge until warmed up, the tranny has performed without issue. Yesterday drove @ 200 miles and went to bed with a smile on my face thinking of how well the car performed. Today @ 15 miles into a short drive I received a 'gearbox failure' message. The car was performing normal. Upon restart a bit later the message never reappeared. I drove home and when I was a few miles from the garage I got a no cruise message...then the message went away...2 miles latter while coasting down a slight grade the transmission felt as if it downshifted into 1st and remained in that gear until I moved the gear selector, then it performed normally.
Got home and used generic obll reader...no codes. I haven't loaded my jlr software to a 'cloned' interface as yet (was awaiting vers 1.3 before I did that).
So...should I be a little concerned or 'really' concerned...or do I need a deeper read of the codes before coming to any conclusions?

wj

 

Hi wj,
No trans expert here, but have a read of this thread:
https://www.jaguarforums.com/forum/x...05/#post845225

...to get you started.
rflexible's post #9 made me chuckle...

HTH,
Mike

 

Recheck the fluid level.

 

OR . . . unless you have already tested your standing battery voltage and can quote it as >12.6V . . . order a new battery, because the cruise and a/t "faults", limp mode, amber MIL on then off, should soon be followed by ABS "faults" and all the time . . . a complete absence of any codes.

Really, the hundreds of such identical or similar experiences throughout these forums, should demand that we start ingraining members with this quick and simple test. Now, your issue may not be a failing battery . . . but it must be the default starting point. So endemic has this issue become, especially among the "modern" Jaguars of the decade commencing mid 90s, that a bunch of us here, from all corners of the globe, got together to produce "Battery 101" and you will find it in the Sticky "HOW TO . . ." of several forums.

2c just ran out . . .
Best wishes,

Ken

 

Michael…thanks for that link, read it and put into the ‘repair mix’.


Gus, thanks…I guess this is the (hopefully) the fix, will do this in a day or so. I had planned on driving for a couple of months and then doing the mercron sp swap once more but this time with a new valve body that has the improved components (that reduce pressure loss)…still hoping I can put this off for a while, while. It was running so well, I’m really disappointed.


Cat_as_trophy
You are correct, I have not measured resting voltage and should do so but I generally have the battery on a B-Tender. This apparently means little but the battery is a bosch unit which is less than 9 months old and as I indicated, B-T is used whenever the car is parked for more than an overnight rest. I will pay attention to the resting V, soon.

 

I thought it might give you a little comfort by suggesting some relatively painless possible causes , as emphasised by Gus & cat.

This is an issue with the 5HP24 fitted to the older XK8s. Your car has the later 6HP26 trans which is more robust.