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Some of you may recall my previous posts about a transmission issue. Long story short, the transmission clunking noise was due to an impending failure inside. I had the transmission rebuilt at a reputable shop with decades of Jaguar experience.
But we still have a problem. It still doesn’t shift correctly after a long drive. In start and stop driving AFTER IT IS GOOD AND HOT, the transmission wants to stay in second gear. Only after letting it cool for 30-60 minutes can you resume driving, until you’re in start and stop traffic again, at which time it has the shifting problem again. The clunk is gone, but the shifting issue remains. The car is still at the shop being sorted out.
The shop and I are stumped. There were obviously two problems, the tranny itself and this shifting issue. Did one cause the other? Not sure yet. Something is telling the car that it needs to be in second gear after it gets good and hot. We think it’s computer related, or a faulty part that the computer is interpreting incorrectly.
We have tried a different transmission control module, no dice. Tried an EGR valve, no dice. There are no codes, never have been any. We are going to try a new fuel filter. Perhaps it’s plugged just enough that the computer interprets it funky. Throttle position sensor? Oxygen sensor? You would think there would be a code if it was something like this, but no codes. Maybe a sensor is sending information, but the information is wrong. The system thinks it’s ok, but it’s not, therefore throws no codes, it just thinks second gear is the answer.
Sometimes getting it up past 4000 rpm will get it to shift. As you can see, we’re stumped for the moment. Why does the car think it needs to be in second gear?
ANY thoughts, no matter how random, would be appreciated! Thank you.
Have you tried driving it manually before and after she's hot?
I have. Manually shifting through the gears makes no difference except that you can manually force it to downshift if it has upshifted. I can’t get it to upshift if this problem is active. I can put the shifter in third or fourth but it stays in second if it’s of the mind to do so. Nothing I do will make it upshift except sometimes around 4000 rpm it will upshift. But then once I need to slow down or stop at a light, we start all over. The sport mode switch will force it into first when stopped or at very slow speed, which is normal, but once it shifts to second, there we stay. Before it gets hot I can bump it into third and it will upshift like normal. In fact, before it gets hot it shifts perfectly normal in all conditions, both in sport mode and regular mode.
You can give the manual shifting a try, but my money is on the 2nd gear shift valve is sticking either because of incorrect part, damage during rebuild or debris introduced during the rebuild. When the fluid comes up to the temps you are seeing in stop and go, the components are reacting by changing size due to the heat.Result is stuck in 2nd until things cool down.
You can give the manual shifting a try, but my money is on the 2nd gear shift valve is sticking either because of incorrect part, damage during rebuild or debris introduced during the rebuild. When the fluid comes up to the temps you are seeing in stop and go, the components are reacting by changing size due to the heat.Result is stuck in 2nd until things cool down.
And no body wamts to reflash the tcm with software and clear adaptations even though that is the first thing zf tells you to do for the clunk, codes and many other issues. And not surprisingly most times it fixes the issues all for a paltry 1 hour charge at a dealeship or at least a shop the has the latest software from zf which most times does not seem to be tranny shops. Kinda like when i had 4 foundations company salesmen come to my house and every single one of them said yes you need has us level the foundation for $15,000. So i hired a structural engineer for $300 and he said nope the tilt is .6%. Anything under 1% we consider fine, have the oak tree roots blocked from under the house from drawing water and you will be fine. Moral of the story is you will get what they sell if you go to someone in the business of selling something to you.
And no body wamts to reflash the tcm with software and clear adaptations even though that is the first thing zf tells you to do for the clunk, codes and many other issues. And not surprisingly most times it fixes the issues all for a paltry 1 hour charge at a dealeship or at least a shop the has the latest software from zf which most times does not seem to be tranny shops. Kinda like when i had 4 foundations company salesmen come to my house and every single one of them said yes you need has us level the foundation for $15,000. So i hired a structural engineer for $300 and he said nope the tilt is .6%. Anything under 1% we consider fine, have the oak tree roots blocked from under the house from drawing water and you will be fine. Moral of the story is you will get what they sell if you go to someone in the business of selling something to you.
I agree with all that, especially your signature about Parts Geek and brake parts. I can’t say 75% but I can say that the one time I ordered brake parts from them, they were wrong.
Back to the tranny issue....we swapped in a used tcm before we started but it didn’t make any difference. Who or what is zf that you referred to above?
i agree with all that, especially your signature about parts geek and brake parts. I can’t say 75% but i can say that the one time i ordered brake parts from them, they were wrong.
Back to the tranny issue....we swapped in a used tcm before we started but it didn’t make any difference. Who or what is zf that you referred to above?
argh forget what i said earlier it doesnt apply to your car. I go in all the forums and sometimes i dont realize im speaking about a newer or older car when the poster has a different model. Happens more the older i get. Zf manufactures the trans for jaguar, land rover, benz etc and on the later models for which my statement applies. You can have a drum failure which is the clink and a failure mechanically.
I had a similar problem after putting a new gearbox in. Now, last week, I cleaned PPS and TPS contacts and replaced a shot O2 upstream sensor in the left cylinder bank. No more transmission clonks or gearbox fault mentions anymore and she goes like a bat out of hell (for the time being). Scanner does not find any problems anymore either. Hope this will last.
I had a similar problem after putting a new gearbox in. Now, last week, I cleaned PPS and TPS contacts and replaced a shot O2 upstream sensor in the left cylinder bank. No more transmission clonks or gearbox fault mentions anymore and she goes like a bat out of hell (for the time being). Scanner does not find any problems anymore either. Hope this will last.
For what this is worth,
Takeo.
We still haven’t figured out this issue. If you don’t mind, what is PPS and TPS? I’m willing to try anything at this point.
We swapped out my newly rebuilt tranny for another used unit, not rebuilt, but previously working. No dice. That tranny won’t shift either. This confirms that the problem is electronic, in some form or other. We are in the process of getting a used engine control computer. A tranny control module swap made no difference.
Any more advice? Keep the suggestions coming! Speculation is encouraged.
This is very helpful thank you. Do you know where the pedal position and throttle position sensors are? Is the TPS built into the throttle body, and / or is it replaceable without replacing the throttle body? I don’t know where the PPS is, unless it’s the same switch as the one on the brake pedal that activates the brake lights. I replaced that switch a few years ago because the cruise control was acting up. It fixed the cruise problem. If that’s the PPS, a faulty sensor could still be the problem. It may have been a used eBay switch that I bought.
In the manual you linked to, I see a vacuum modulator that is associated with the throttle position. My car is an early 1998 XJR, but I don’t know if it has this modulator. If it does, it’s possible this could be the problem. I’ll keep digging. Thanks again for the link. VERY helpful!
09-24-2018, 02:36 PM
Transmission shift issue
