I am not looking to fix problems that don't exist, in fact, this post is about being penny wise, not pound foolish.

After reading a few recent posts about the 6 speed automatic in the 4.2 cars where owners have complained about some harsh 2-1 shifting/clunks, and sometimes iffy 1-2 shifts or other shift quality concerns, and my own consistent 2-1 clunk for more than 40k miles, I began thinking more about this. And Steve's (whitexkr) recent response to one of these posts stating that these transmissions should be smooth, had me thinking even more about this so I started to do some research. What I am reading leaves me with more questions than answers.

I have found some references to known issues with mechatronic (valve body) units causing harsh 1-2, 2-1 shifts, shift flare between 4-5, and other shift quality issues. It appears that there are "upgrades" to the mechatronic unit that correct these issues. I also have read that just replacing the solenoids resolves these issues. Finally, I read at one site that if these issues are not fixed, it can result in further transmission failure requiring an overhaul.

So my questions: does anyone really know if that last statement is true? Is resolving these issues necessary to prevent further damage, or are these issues only what I had always beleived, nuisances, or damaging if left? Is a mechatronic unit replacement a preventive measure to a complete overhaul or replacement of the transmission?

Upgraded mechatronics are about $1000. Solenoid kits run about $600, but I don't know if just solenoids would be as good of a preventive measure toward possible future damage, if any of this really is necessary.

I know that I have read there is an upgraded mechatronic for the ZF 5 speed which supposedly does prevent A drum failures, but I have never heard of any 6hp26 experiencing A drum failure, or really any other major internal failures. In fact, all I have really ever seen is that these complaints seem to be annoying, but not destructive. I have only seen a few posts about owners having to replace the 6 speed, and as I recall, these were done early under warranty.

Finally, for about $1000, I might consider replacing my mechatronic, and I read the ZF instructions on how to replace it (on a BMW), but I am really not sure I want to tackle it myself. Has anyone here done this and can offer advice?

 

My wife began complaining about sporadic harsh shifts in her 2006 XK8 in the early summer of 2013. I decided to do a pan/sleeve/ATF change using Klaus' CTSC kit for the 6HP26. That helped, but did not completely solve the issue. Several forum members recommended having the ZF Transmission Adaptation Drive Cycle IDS reset procedure performed by a trusted dealership. I did some further research, then decided it could indeed be the most cost-effective next step. I cut a deal in late July 2013 with the Greensboro dealership to have this done for $175 (some dealerships charged $250 or more). The new pan/sleeve/ATF combined with the Drive Cycle IDS reset procedure flat-out fixed her harsh shift issues. More than 20,000 miles later, I haven't heard a single shift-quality complaint from her since....

Before you tear into your ZF and drop some serious bucks on parts, I strongly encourage you to try the Drive Cycle IDS reset procedure. Be sure to negotiate a better price first....

P.S. - I considered a couple of indie shops who claimed they could do this procedure, but they just did not have enough experience with it to be able to convince me that they could successfully pull it off. I believe this is one procedure where you're better off going to a trusted dealership....

 

Thanks Jon, I forgot to include in my initial post that at 62k miles I had the fluid/filter replaced, and then had the TCU reflashed and went through the drive cycle procedure. I did this to resolve a harsh up shift from1-2 and It has been fine since.

Occaisioanly I have a sort of "un-smooth" 1-2 shift when in sport mode, as if the transmission decided to shift, then changed its mind, then did it anyways. if I use medium accelerator pressure it seems to happen sometimes, but with very light, or hard acceleration it shifts fine.

My 2-1 downshift clunk when coming to a stop was never resolved, and it does this nearly every time I come to a stop, only once in a while it is smooth.

 

This sounds like the classic 'lurch' first made famous on the 2002.5 S-types.

 

didn' these transmissions get TESTED before put in cars to catch this crap?? Then the car maker does not cover the costs to fix it.

 

You can test new transmissions on the bench all day long at the factory. But once in the real world with significant miles behind them and ATF degradation in full swing, abnormal behavior begins to occur....

Reason No. 147 why these ZF boxes should have been designed with a dipstick/fill tube solidly in place....

 

Keep in mind that the shifting is controlled electrically and everything related to it must be correct this is from the shifter cable adjustment to the linkage that operates the shifter selector switch on the other side of the trans to the transmission control module and back to the transmission valve body. I have had to adjust my cable to get it to shift into 2 properly. I have been told that the “O” rings & springs in the valve body in the trans have been upgraded in replacement valve bodies.

 

Yes, but it only affects some cars and only when driven in some ways. It was found on BMW and Audi cars but also our cars. Same sort of fixes on all of them.

 

Can you name any product more complicated than a stick that has gone out to the field which was absolutely free of all defects and quirks?

 

Steve,

Let us know what you come up with.

 

Thanks, I will Gus.
I started here, looking for unbiased actual experience, and didn't expect any really, because I have seen very few posts on this forum about issues with this transmission. I am going to search through some BMW forums to see if they have had any real/world experiences related to this.

My last resort will be to go to a ZF specialist in Jacksonville, although, my concern is, will I get a true unbiased response? I would like to beleive I would, yet they are in the business, and in business, to make money. There are many things in life that if you look, you will see something that needs or could benefit from an expert, and sometimes only an expert is who can see. For instance, I have been in computers for 30 years. While I am a manager now so I don't know anything anymore, I know enough and can look at someone's computer, even if it is working fine, and can find things that need attention, some of which could prevent issues later on, and some that if not fixed, wouldn't really matter. I know the truth about it, and can give an opinion. I hope I can find an expert who will tell me the truth about this, and give their unbiased opinion.

 

I am no expert in the area of transmissions but I had to get familiar with it to identify the truth or BS. I do have a trans shop that is in Md. that I trust but I see that is not going to help you. The big problem today is that most people want to just R&R an item (your money) and troubleshooting is a thing of the past.

I feel I need to ask this question but have you done a hard reset to see if that clears the problem? If that does not work try putting your shifter in the manual mode and I think yours says “5” and drive the car and see if you see a difference the car will shift itself up to gear 5. This was the only way I could drive the car until I could get the linkage adjusted.

 

hard reset can fix possibly the trans shifting crap in the 03-06 xk's? Hard reset if what again? crossing the batt cables with them OFF the bat for 30 seconds?

 

The hard reset takes the transmission and all other control modules to factory specs.

 

But it doesn't clear the transmission adaptations.

 

Yes that is what i have been told.

 

FYI I just pulled this from a Jaguar training manual

http://www.jagrepair.com/images/Trai...2002-20-02.pdf

Page 20

“Approximately 80% of all control units that are replaced have a software problem that can be either corrected by performing a hard reset (disconnection of the battery power supply) or reprogramming of the hardware. It is sug-gested before any modules are replaced a hard reset and/or reprogramming should be carried out. Several options are available with WDS: Program New Module, Program Existing Module, Dealer options, Setup and configuration.”

 

Thx Gus, that's a great document.

I had the transmission control unit reflashed by the dealer at around 65k miles or so (102k on the odometer now). It resolved the chronic harsh 1-2 up shift, but never helped the 2-1 clunk when coming to a stop. I know I read a technical doc somewhere that said the transmission adaptations are only reset with the dealer tool either when a reflash is done, or specifically to set up the adaptations drive cycle. Regardless, I have done several resets by pulling the battery ground cable and holding it to the pos terminal, no affect.

I am not necessary try to fix anything, rather, wondering if the downshift 2-1 clunk is a symptom of a mechatronic problem that if left as is, could cause more serous and expensive future damage. That really is my big question. If someone told me I could spend $1000 to avoid spending $4000 in the future, I would do it.

Now, one thing that occurs to me about the clunk 2-1 downshift... If anyone here recalls, I recently (at 98k miles this past summer) had to replace the throttle body due to bad TPS. An unexpected result of that: when coming to a stop, the car now seems to coast, as if the transmission disengages. This was a significant difference from before the TB swap. In fact, so dramatic it was that I frequently momentarily thought the engine stalled when coming to a stop. Regardless of this coasting feel, it still would/does clunk downshifting 2-1. So, I was thinking, if my TPS had always been incorrectly adjusted since I owned the car (as suggested by this lack of coasting to a stop since I have owned it), then the drive cycle adaptation I went through when the TCU was reflashed, could have been skewed by incorrect throttle position readings, and therefore, my adaptations/clutch pressures may not be optimal. Therefore, I am considering another dealer reflash.

 

The ECU & the TCU and all the other control modules must talk to each other do a hard reset and see what takes place. What is the actual RPM that the car sits at when at idle? Could this harsh downshift be a broken transmission mount?

 

Idle is consistent, 650. I hadn't thought about a transmission mount.