An update for those who have been following my saga over time. I installed a different TCM a while back, but hadn’t had time or hot enough weather to test it, until today. Same problem. After a long drive in HOT WEATHER, followed by stoplight to stoplight driving, my car will not upshift until 2500-3000 rpm. In addition, when coming in to stop for the next light, it will downshift harshly through the gears, like you threw on a Jake brake.

I’m starting to wonder if the transmission case itself has a crack or chip someplace inside, that once it gets really hot, it expands and lets fluid seep through. This may be causing internal pressure issues that might lead to this problem. It could be a crack or chip on the case-side of the mating surface with the valve body. Since the valve body has been replaced, I’m going to believe the crack is not on the valve body (for now). The transmission was rebuilt, but the case is the original.

Is this possible? Are transmission cases normally tested for such issues during a rebuild? Obviously I’m still reaching for straws here, but any thoughts along these lines would be appreciated.

 

My 98 XJR would do something very similar. After a bit of online digging, I was fairly confident the issues were in the valve body. the benz forums are a cash of info https://www.benzworld.org/threads/me...n-faq.1463460/ along with the sonnax website https://www.sonnax.com/tech_resource...5-jaguar-722-6 . Plan was to replace the 2-3 pressure regulator spring https://www.benzworld.org/threads/72...ement.1423078/ but ended up buying a mint 2003 XJR R1, so the 98 sits for now.

 

Thank you for this. I, too, have done online digging, including the benzworld forums based on past suggestions. My transmission was rebuilt last year, which helped the clunking sound, but the shifting problem remains. The problem could be in the valve body, but it was supposedly replaced during the rebuild. I dropped the valve body out a few months ago, just for my own curiosity. I verified that there was a newer date etched onto the valve body and conductor plate, which led me to believe both had been replaced. I also specifically asked the shop if it had been replaced. They said they replaced it, but I did not see the old valve body, so I guess I don’t know for sure. It’s possible they just etched a date on mine and re-used the valve body, I guess.

I’m revisiting everything at this point. I am tempted to get a valve body, conductor plate, and solenoids, and do a fresh install. I wish there was a way to know before I spend the money. It’s a pretty quick process to replace that stuff, so I’m not concerned about that.

Do you know - Can I order a complete valve body, with solenoids and a conductor plate from sonnax? Or do they only sell to repair shops?