I have had my 2004 XJ8 for a month now and am enjoying it even more than I thought I might. I have read on this forum and other places that the transmission (when new or after having the adaptives cleared out) will "learn" the driver's driving habits.

Mine has the occasional "thump" into 2nd gear from 1st that I can usually get around by taking off a little faster. It is very hard to control it when the car is rolling with very little acceleration like from a very slow take-off or in stop and go rush-hour traffic.

I've read about having the transmission flashed, etc.. But I've also read that sometimes such issues as that can go away just by clearing the adaptives and letting the transmission learn the new driver's habits.

That set me to wondering if there is a limit to how much the transmission can learn. By that I mean, is there a set number of data points that it records and uses, then learns no more? Or does it continue learning and replacing information, based on new habits, perhaps adding the newest info and deleting the oldest?

If the latter were the case, it seems that the car would eventually learn the habits of the new driver and, over time, wipe out the old input that it had been operating on. If that is the case, how long should the car take to "transition" from one driver to the next?

Thanks for your input.

 

to my knowledge, it learns the most on the first 200km after an adaptation cycle.
old tcm-versions are said to drift.. maybe that's some kind of learning, too...

 

The only real downside to adaptive transmissions (first developed by Chrysler in the late 80's & licensed to MB in the early 90's) is when the car is driven regularly by multiple drivers. Depending upon the various drivers time behind the wheel and their driving habits the car can feel odd or acting-up to each different driver in turn. In fact varying your own driving style just confuses it and teaches it the wrong things.

Of course your problem could be a problem with your tranny or it's control module but I'd first make sure it's fluid levels are correct and quit trying to 'fool it' into doing something. Drive like you normally do in the kind of traffic you drive in most and if the problem doesn't resolve itself have it checked.

 

I understand you to say that the transmission will eventually adapt to a new driver, which is what I hope it will do. I am the only driver except for rare occasions such as might come up next month when we put my Honey's DTS in the shop for some warranty work.

The "thump" from 1st into 2nd that I mentioned is not something that I am worried about, but I do notice it when it happens. It may be my imagination, but it seems to be happening less often lately.

You mentioned being sure the transmission is full of fluid. Short of taking to a mechanic, how would I do that, given that there is no dipstick on these cars?

Thanks.

 

bookman:

I am told by my local Jaguar dealer that there is a shift point around 30 mph that is often not smooth with these cars. They were not promising any dramatic improvement if the transmission is reflashed and/or the transmission flushed and refilled. As you point out no simple process to check fluid level.

Interesting to note ,we are owners of a 2004 XJR with 81K miles and a 2007 DTS with 166K miles. Not to diverse too much in a Jaguar forum, I suspect your DTS has not given you many problems. Wheel bearings start to go around 100K miles.

RyeJag

 

I do not know about the ZF tranny, but in general, what a transmission learns is the condition of the pistons and clutch packs. In otherwords, a brand new tranny, with perfect seals and fat clutch packs will engage and disengage the gears quickly. A worn tranny, with not so perfect pistons seals and worn clutches will engage and disengage more slowly. The tranny compensates for this and alters the trigger times for release and engage so shifts remain consistent.

ZF likely threw in a function of how often you "punch it" versus someone who never punches it, so the tranny may learn to be more or less ready for down and up shifts. Again, this would simply be a change in shift trigger points, not major changes in shift quality. So, a tranny that has not learned your style may seem reluctant to downshift when you think it should. Likewise, if an aggressive driver drove it before you, it may seem to linger in a lower gear longer than would seem normal before upshifting. It will eventually "learn" to adjust those shift points better to your liking.

If you have a consistent hard shift, especially between one set of gears (like 2-3 shift)...I don't think it is going to be able to "learn" that out. There is something worn beyond it's ability to compensate. Again, I am just expressing generalities, the Jag could be, and often is, different.

 

Funny, you should say that. We just took a Thanksgiving trip out of state in the DTS. The car has started making rough "growling" sounds in the front end when coming to a strong stop, such as at the bottom of a down-hill Interstate off-ramp. I have not removed the wheels to look at the pads, but the rotors don't show the kind of wear that I might expect if it were badly worn pads. I told my Honey that I suspect wheel bearings might be the problem. I don't notice the issue with normal flat ground slower stops. We have a bumper to bumper GM extended warranty on the car that expires in April, so I am going to take it in and get three or four things tended to. Wheel bearings are a covered item, so I will add them to the list if I find that they are going bad. Every item that they repair on one warranty is covered by the same $200.00 co-payment, so I intend to report every legitimate issue that I find on it before the warranty expires.

As for checking the fluid on the ZF transmissions in the Jag, I found the fluid check procedure in the shop manual after I wrote the OP. Seems quite primitive, actually - drive the car until the transmission is sufficiently warmed, raise the front of the car, remove a certain plug. If fluid runs out, the transmission has plenty of fluid. If no fluid runs out, the fluid level is low. Fill it until it runs out.

In my day job, I have driven many large vehicles - trucks and especially high-end coaches with 3000 and 4000 series Allison automatic transmissions. They have dip sticks, but I can also check the fluid level from the driver's seat by pressing a certain combination of buttons on the shift pad, then let it run through its short process. It will either say OK, or tell how much fluid to add. Too bad a transmission as advanced as the ZF can't have such a feature.