I've noticed I will occasionally get a very hard and abrupt 3-4 shift. Most time it's happened when I'm going slightly uphill at low speeds. Never when starting from a dead stop. Seems like it's happening more lately. Now that I'm paying attention to shifts, I also notice under normal shifting the 3-4 shift is more noticeable than any other shift at low speeds. No shift noises and no other shift problems.130k miles on the odometer. Trans oil was changed once before at 65k miles.

Looks like this may be the E clutch pack? I was planning to do another fluid change soon. Should I reset the adaptations after that and see what happens? I just don't want to make it worse. Looks like I can reset the adaptations with SSD, then take the car on a drive to relearn? (low speed upshifts, coast down, etc). Or do I have to do the procedure where SDD is live while driving to relearn?

 

mhamilton;

I believe I am experiencing the same problem (04 XJR, 100 kmi): infrequent occurrence over past 20 kmi, normally occurs when car is moving ~30 mph, normally occurs when I let off the brake and move onto the gas. It always sets my MIL but resets when I restart the car. Seems to be fluid level and temp independent. Occurred before and after fluid/filter change (Lifeguard 6). My code reader reports P0783 "3-4/4-3 Gear Load Fault." I'm curious to hear what you and others have experienced with this. Here's a few links I've been reading.I'm contemplating replacing the mechatronic seal and the four tube seals between the mechatronic and transmission hoping this may be age related pressure loss.
Looking forward to experiences from other forum members.

Best Regards, William

 

Clearing adaptations does no harm. You can just drive normally (not like an idiot) and the gearbox will adapt OK.

The procedure can speed up the adaptation but is not necessary.

bob

 

William,

My old 2004 XJ8 had the P0783 issue.

Changed fluid, filter, sleeve, mechatronic unit with a known good unit, bridge seal and the 4 tube seals and refreshed TCM with SDD and did adaption drive cycle.

Very little improvement but still had 3-4 upshift issue.

It was the E clutch.

I would check fluid level at 40 dec C and make sure you have a dribble coming out to rule out low fluid level.

But experience leads to a E Clutch on the way out.

As a last resort you can reflash the TCM with latest firmware and drive the car gently as motorcarman suggested for about 200 miles, no sports mode.

 

Interesting... I was wondering if replacing the trans internal seals and/or solenoids might help. I've never had the car set a fault code related to the hard 3-4 shift. It's so intermittent I couldn't get it to repeat if I wanted to. And actually it's been doing it randomly since 50k miles, so I'm hoping it's just adaptations.

I'll plan to change the fluid and reset the TCM. Is there any data PID I can look at to see if my E clutch is on the way out? LIke if there's excessive shift time?

Thanks again,
-Michael