Symptom: When moving the shift selector from Reverse to Drive there is a 1 second delay before you feel positive forward pressure. If the accelerator is pressed immediately after moving from R to D, without waiting for 1 second, there is a slight lurch with an associated clunk.
Testing: The ZF 6HP 26 transmission shifts normally, up & down, once moving and under any degree of acceleration. The only way to get the problem to repeat is to select R then back to D. The 1 second delay occurs always.
History: the car is a 1999 XK8 convertible, normaly aspirated with 85,000. The transmission filter and oil were changed at 60,000. Oil was Esso ATF LT 71141. No problems at that time. The car now has 85,000 miles. It was borrowed for about 1 year by my brother. He ran over a tire on the interstate and transmission fault codes appeared. He had it serviced by the local Florida dealer who commented upon arrival, “we don’t like to work on these old cars, but since you are here we will do what we can”. After $4,000 worth of work, over several visits, problems continued so I had the car transported from Florida to New Hampshire and started to work on the problem. The first problem of DTC P0121, Throttle Position Signal due to incompatible metals used in a connector and the car defaulting to safe mode was resolved by identifying a loose connector at the throttle body. Tech Bullentin 303-58 had already been worked several years earlier by the dealer in Indianapolis (excellent service BTW) so I knew it could not be the metal. It turned out to be a connector that was loose. This had been completely missed by the Florida dealer. The car now worked perfectly, no codes, except for the R to D shift delay. I changed the fluid and refilled following the refill procedure in the Jaguar Workshop manual for automatic transmissions using Febi bilstein Nr. 14738 which meets all specifications. I replaced the trans fluid in case the dealer used the incorrect fluid.
Next steps: It is my plan now to again replace the transmission fluid and the filter. It is possible the dealer in Florida did not seat the filter properly or used the wrong filter, or didn’t change the filter. My guess is there is something that is allowing the pressure to drop during the shift from R to D but is not impacting the normal shifting pattern or responsiveness.
I am at a loss at this point and guessing. If anyone has any good ideas to try I would love to hear them.
Thank-you for reading my story!