It worked very well - much better than the little hand pump we used previously. Had to remove the restrictive wand and fasten a length of vinyl hose to the "trigger", but once that was done it was smooth sailing!

 

Great News Mickey, hope to see you in late July in Townsend. Anything special yet for Oct?

 

Nothing yet - I mentioned it to Rick, maybe expanding it a bit to make up for the cancelled annual; but no word back from him.

What's happening in July - y'all headed this way?

 

Good to read Micky R.....very good indeed!
What is the core charge amount?

Keep driving and enjoying...

 

$500!!

 

Yeah, I was not expecting less.......and I would have shipping cost.
Is the "core" everything....meaning, valve body, TCM, solenoids....or just valve body? Just curious as I wonder if there is a company(s) that is rebuilding everything, or just the valve body.

 

As mentioned above, the Mechatronic unit is a package that includes the valve body, TCM and solenoids. Really is "plug-n-play" once it's programmed to your car's VIN. And this is a ZF-rebuilt item.

 

Thank you, this has been one of the most complete threads that I have read on the 2 to 1 harsh downshift (type 1 lurch) and I have read hundreds including the BMW forums and others.
However, for me at least, I am still a little confused. Being that the car now has a new TCM, with what I assume would have the latest software updates, and a new valve body and solenoids, where does the actual issue stem from... Software or hardware?

 

OK - to recap, in a nutshell: This began with the harsh 2-1 downshift when pulling to a stop. That, coupled with the occasional "squawk" during upshifts under power. From what I'd read here, the common remedy for these was to refresh the transmission fluid, along with filter change and replacement of the bridge seal, the connector sleeve seal, and the four tubular valve body seals. I did all of that, and a few short drives and it seemed better, but it was my understanding that a reflash of the TCM was required, so took it to the local Jag dealer to have that done. However, when they attempted to do that, they could not get the TCM to communicate with their computer, and subsequently the transmission went into limp mode. I was then told by the tech that a new Mechatronic unit was required, as the TCM and the valve body are integral.

I contacted ZF's tech support and was told that my issues were indeed indicative of a failure of the Mechatronic unit and a rebuilt replacement would be needed. They recommended the vendor (Whatever It Takes Transmission Parts), as they are selling agents of the rebuilt units that ZF supplies, and there is a branch location in nearby Knoxville.

As for the exact cause of the whole mess, these are my findings, all of which are purely conjecture on my part: The car, a 2003 model with only 18,000 miles on it, may not have had enough usage to keep all the seals lubricated over time. Which may have been the cause of the squawk and the harsh downshift. And then when we did the fluid replacement, we did not know that the battery was supposed to be disconnected before removing the Mechatronic unit, and that may have compromised the electronics. Then also, the bridge seal that we used as a replacement the first time seemed to be a bit thinner in height than the original (which I didn't realize until we redid all this), so that may have caused a loss of pressure, which may have triggered a fault to cause the transmission to go into safe mode.
.
Anyway, all I know is that after two refills of transmission fluid and a new valve body/TCM, the car seems to be as it should. I wish I knew exactly what the problem was, but simply glad we're at the point we are... knock on wood! And no one is more confused about all this than I am! Rest assured that the car will be driven regularly from here on out. And enjoyed!

 

I get it completely. I read your thread with great interest, I have the x150 with the same transmission and low miles. Through drive cycle recommendations and driving style I have been able to eliminate any harsh downshift however, occasionally I will feel the shift from 2nd to 1st but nothing harsh. I live in a rural area so more noticeable in stop-and-go traffic.
There are so many theories on what it is caused by and what can eliminate it completely. As I said I think I have read every thread written about the zf 6hp26 2 to 1 downshift. After reading all about fluid changes, valve bodies, solenoid, speed sensors, wheel bearings, etc I have read a couple of other interesting theories.
One is that the TCM has several maps and that for whatever reason (some say low battery issues) the mapping can drift depending on driving conditions or heat.
Another is that the problem is actually not in the transmission but in a signal that the TCM is receiving from the ECM such as a misfire or a problem with a low idle as the car comes to a stop. This is the reason that they say the ECM and TCM need to be reflashed at the same time.
​​​​​
I have no idea whether these are valid explanations or not but being that many cars with low miles (some of them from new) are reported to share this downshifting characteristic, they seem plausible.

Appreciated your thorough right up and glad you got it squared away!

 

Thanks! This was a bear, to be sure. I've restored/repaired/built several British cars, including installing a GM V6 and 5-speed into an MGB. But that's all old school stuff. This newfangled electronic equipment is quite a puzzlement!

Drive on!

Mickey

 

Final chapter in this saga. (Let's hope!)

Yesterday the wife and I drove from home to Crossville TN and back - roughly 200 miles total. The car was perfect - smooth shifts and no hiccups.

I'll add that I've done no "Adaptive Drive Cycle" (or whatever it's called) with the computer software instructing the various steps to take so the TCM can learn how to shift. My guess is that since the TCM was supplied pre-programmed to the car's VIN, it was only necessary to drive it over several occasions as it would normally be driven and it would sort itself out. At least that's what I'm telling myself!

Anyway, glad that's behind me, and we can enjoy this beauty as it's meant to be!

Thanks again for all the help, folks - now on to the next adventure...

Cheers,
Mickey

 

I have the same harsh downshift and sqwark with 126k miles on mine. have changed my filter and fluid but did not have the ***** to remove the valve body and change all the sleeves, etc. My car is on jack stands and my garage is very dusty so I wanted the pan off for as little time as possible.

I hope what i have done is enough to have some effect but not driven it yet as I have some more work to do before getting the car back on the ground.

Interestingly the ZF 8 speed box in my XE is developing a lumpy 2-1 shift too. On a couple of occasions it has been so bad I thought I had been rear ended at some lights. I spoke to the jag service centre about it as it is still under warranty and of course they say a filter change is not neccessary, just an adaptations re-set. They are going to do it when I take it in for it's 84k service in a couple of weeks so will see what happens.

If the reset clears the problem I may have wasted a lot of time on my XKR!

 

Removing the valve body and replacing the seals is MUCH easier than refilling the transmission! Though seemingly intimidating, it's really pretty straightforward, but does take two people - one to hold the body in place while the other removes the last few bolts. (Unless, of course, you have four hands...)

 

No chance of a helper for me. I made relatively light work of filling the transmission by using a little 12v oil pump connected the battery with jump leads...




Hardest part is getting the plug back in!

 

I have done it on my own without any trouble at all.

And yes its much easier than refilling the transmission.

 

The theory is that the adaptation are meant to tune the PWM to the solenoids based on YOUR exact transmission, in its current status (fluid age, condition of the clutches, etc.), not for any other transmission just like it. For all we know, this adaptation was triggered on the bench by ZF right before delivery to you. To my knowledge, the real adaptation/learning occurs during the 100 miles after the software procedure is completed.

Glad to hear it is all working out.

 

^^ What he said....

 

Thanks, guys.

 

Hey MickeyR....in case you are still reading this thread.....
Finally got around to doing the fluid/filter/seals change, just finished an hour ago. I had a slight glimmer of hope that new seals would fix the surging problem. Took it out for the test drive and as expected, no change. Looks like a rebuild mechatronics is the only way to fix this...which is what I was told by Jaguar dealership 5+ yrs ago. But now that I have experience taking the mechatronics out and everything.....wife and I have to decide if car is worth spending the $2k or we just continue driving it as it is.

I had trouble getting the mechatronics back in...or so I thought I was; I was expecting it to be more of a "click" into place....but it did not. Anyways on the forth attempt I got it in and then continued with the filter and then fluid fill.
I was only able to get about 2.5L initially. But after starting engine and shifting to D, R, then Park twice. Shut it off and was able to get just over 5L in. I may be a tad bit low, and I might add another 0.5L since I have pretty much nothing else to do.

Anyways hope all is well with your Jag.....

Later,