I have read on a few other threads but they are all 10 years old at this point. But my revs when the transmission is cold go up and down by about 50 rpm if that when at constant throttle between 40-50mph. I have read that it is many different things but no one has really said if it can cause failure of the transmission apart from one individual. It seems very common across all ZF6HP26 transmissons but I haven't seen any specific part that is the cause. Some say it's the torque converter and others say it's the valve body but I haven'ts een anyone that has actually managed to fix it. Some even said it was a feature of the transmission which I have actually seen it referenced in a manual somewhere called modulation of the clutch pack or something. Anyway what I want to know is if I should get it looked at because it has been doing it for years and I would imagine has for many others as well.

 

I drive my 2005 in 3 until warmed up then put it in d, no more hunting.
If you change out the fluid it might solve the issue for a while. Don't know if it iij s a trans part failing as opposed to a general wear factor. Pretty certain new clutches would solve the pop problem but at that point probably rebuilding would be better option.
Btw, my 2008's trans feels like a completely different animal and is a total joy to use, so improvements were made over the years.
wj

 

I do like the X150 cars but the biggest problem I have with them is the severe lack of wood and the exterior design isn't as sexy. The X100 is a really clean interior design which I like a lot. I do like that the X150 won't rust as much as the X100 either, that is very enticing. The tax though is pretty painful on them.

 

This is a thread I'm keeping eyes on as my 2002 XK8 has been doing this for as long as I can remember. However, more recently it appears to hunt now at 45-55mph. Previously it was limited to 30-40mph whilst on inclines.

 

Mine has always been around the 40mph area. I think it's more dependant on the load not the actual speed of the engine though. It may also be the adaptations, an oil change may change it a bit after they have been reset? I have just been driving in 3rd and keeping the speeds down until the transmission has warmed up, once it's warmed up it never does it.

 

I had this issue on a 98 XK8 with ZF5HP24. An 'expert' suggested it was a throttle body issue. After research I felt it was a torgue converter issue. Bristol Transmissions were willing to change the torque converter for around £1600 all in but then a low mileage ZF5HP24 came up on eBay for £1200 fitted so I went for this. This resolved the issue so was definitely gearbox related but not necessarily torque converter. I believe I've also seen something about a software update resolving this issue on later models.

 

Yea I have also seen the software update but some people that have had the update said it still didn't go awway. It's hardware related for sure but no one really knows if it's signs of a catastropic failure or not. I don't think it is considering a lot of people and me included have driven on it in these conditions for years with no failure.

 

Agree on the X150. I think wood may have been an option but haven't confirmed. Exterior color makes a big difference. Ian Callum's preference was apparently Radiance Red. It softens the sharper edges (around the headlight area for instance) and the car looks slightly more like a classic X100. Darker colors and the X150 is very different car. Fun to drive but, as we all know, it's impossible to beat the X100 style inside and out.

 

I have seen a few cars with some wood inside them but I'm not sure if it's from the factory or aftermarket because I have seen some aftermarket wood panels for them. I haven't driven an X150 Jag but I have been told they are very nice cars to drive. Are they more comfortable then an X100 though? Handling wise the X100 is perfectly fine for road driving even fast road driving in my opinion. It's not a track car it's a GT.

 

Aftermarket wood? Interesting. X150 feels more like a high performance sports car. Lots of fun to drive but an X100 is GT comfortable.

 

Interior wood trim - Jaguar Forums - Jaguar Enthusiasts Forum

 

Thanks. Just noticed you own an XKR. Yes the X150 is "sporty" but of course a supercharged 4.2 will leave it in the dust. Just drove an 01 XKR. Great sound under full acceleration. Having owned the non R version of a first gen and now a second gen, am familiar w/ the differences. Is there the same noticeable difference w/ the R versions? 5 vs 6 speeds will factor in.

 

My experience with trans issues with my 2004xkr is long, sorted and I won't bore you with all that... And what I say next, in reading a lot about the 6hp trans, is speculation-ish kinda but I'll just say it. I've never really heard it mentioned in a lot of what I've read,,, but what about fluid temp, it's interpretation, the sensor and this issue (which I also experience)...

Since it seems to be a temperature related thing, what about the temp sensor?

I flushed and filled my trans a couple of days ago and removed the old stuff while the car was still quite hot. I noticed the difference between cold and hot fluid. The hot was like water.

The 6hp shift strategies are in part based on fluid temperatures... Could a failing reading or bad reading (due to aging wiring and harness) or a failed temp sensor be responsible for this? Just wondering. There's a PDF attached.

Wondering what folks think


Sorry for the poor image quality.

 

You might be right. Sounds more probable then a transmission failure. I wander if it's even important to change it if it's just a faulty temp sensor. When I get the transmission fluid changed I will have the sensor looked at at the same time.

 

Thing is, I had my valve body in many pieces, and from the description (page 9 of the PDF) is a simple resistor type device thats build INTO - I think it said the valve body or the transmission somehow. I never saw it... I would like to know more about it.