I am new to this forum but was very impressed with the instant and precise answer I got to my A/C question.

You are hereby rewarded with another of my unanswerable questions.

Bought a good looking 2000 XK8 in December that had a lot of little problems for a very good price. At least I still think it was a good price.

Got all of the little stuff fixed and have a few biggeritems remaining. Today's issue is a harsh down shift from 5th to 4th under throttle control. Very harsh! I have researchedthe shifting process through the ZF transmission documentation and see a logic path that call for the TCM and ECM to read speed, throttle position, engine rpm, etc, etcand retard engine timing, release converter clutch and shift transmission all in about 0.25 seconds.

Transmission is a new (rebuilt?) unit installed by a Jag dealer under the Select warranty, now expired,about 9k miles ago. Transmission shifts beautifully up - down, hard exceleration, or light. If you release throttle and allow the downshift without torque it works fine. Throttle down shifts below 4th are OK. Appears that converter clutch only locks up in 5th although documentation says that it can in 4th or even 3rd.

In two locations in Jaguar documentation it is stated that the torque converter is to be replaced as a unit with the transmission. The local dealer, that did the work, says that they would have only replaced the transmission and that is what is indicated in repair invoice. I discussed the issue with the ZF shop in the area and they say that it doesn't sound like an internal transmission problem.

Took a Jag tech on a test drive and demonstrated the problem. They scanned the systems and see no codes set therefore have no idea as to what the problem is. I have been working on personal cars for many years and would say that the converter clutch is not releasing. Clueless as what to doto verify or fix in this electronic age. Can't find any vacuum tubes to test.

Any suggestions? Thanks for any you may have.

Test Point

 

i wud take it back and make them good will it.. there is no programming or resetting of any adaptations.. for your 5hpzf . may need a valve body or trani. Can't remember if the converter gets changed with the trani.. all the other jags they do.

 

I was a little befuddled at the way I left the dealer. The tech clearly saw/felt the problem. They just said they could see no codes and didn't suggest any corrective action. They explained that there were no reflash solutions available. The previous owner claimed $11,245 in warranty repairs over the past 3 years, 19k miles. When the 100k warranty expired and the dealer wanted $600 to replace the MASF to fix the P0171/0172 codes he put the car up for sale. I fixed that problem by taping up the split bellows.

The transmission shifts perfectly, in every way up and down, except for the 5/4 transition under torque. The TB was replaced previously.

I really don't know how to approach the dealer about a good will repair when I bought the car 6k miles out of warranty, 9k miles after the transmission was replaced.They told me, by not even suggesting any repairs, that they do not know where to start.

 

how long ago did they put the trani in? time wise?

 

Sorry, you said valve body, not throttle body. I did see in the ZF technical specification that one of the valves is for the converter clutch.

My question continues to be how to figure out what is wrong without starting to replace major units.

I found in the JTIS a reference to a recording code reading device for use by technicians on a test drive. Would that provide and detail of all the sensor inputs, ECM/TCM actions that occur under the described shift? Does anyone have any experience with the recent Jaguar software for the AutoEnginuity ScanTool? Would that read/record all the TCM/ECM inputs/actions? I've been trying to find a reason to buy that puppy.

Thanks for the input.

tp

 

Transmission was replaced June 21, 2006. A few more miles than I remembered. Actually 18k.

I try very hard to do all my auto repair work and I don't mind pulling the transmission but I really hate replacing large parts that weren't the problem.

 

Hey test, I have one of the autoenginuity tools with the Jag expansion pack. If you give me some instructions on what to do for a test drive, and which mode in the scan tool software, i'll try it out for you tomorrow. I have the day off.

I've only played with it using the 02 sensors to check for rich/lean conditions during a drive. Every other option is untested, per say.

i'll help if I can.

 

Matt,

Thanks for the offer. I'm a little pressed for time this morning but will drag out out all the documentation I have collected and describe the call for downshift sequence. Perhaps late this afternoon. It's here, somewhere, in my computer. Basically, it describes the ECM and TCM inputs and outputs toinitiate, and complete,the 5/4 downshift. If you can verify that the ScanTool candocument a normal downshift I will buy one and see what is not happening with my car.

Again, thanks for the offer. Be back soon.

tp

 

My 97 does that sometimes. I don't know what gears but I do know it only does it when letting off the gas or slowing down when coming to a stop in a hurry. I've been told that it is an rpm surge and not necessarily the transmission. My tranni was rebuilt at an early milage, too. Haven't really looked into it yet. got other problems for now.

Hope that helps. let me know.

 

Both your and mine sound like torque converter clutch failing to release for the shift. I love a puzzle and am going to solve this. "I shall return"

tp