I have a 2002 XJR with the Mercedes transmission. The other day a funny thing happened. I pulled away from a stop, and it felt like it was in 1st gear, despite not being in sport mode. It held onto it up to about 20 mph, then did a very rough change into second.

Apart from this one time, it has worked perfectly and very smoothly (done about 500 miles since I bought it).

It has done 133K, and had the transmission fluid changed at 50K. Do I change it, flush it, or leave it alone?

 

Try putting it in sport mode and leaving it there.

Mine did the same thing a few times before I tried this trick. Has not done it once since I put it in sport mode. Been about a year.

There is a thread on the forum about this and the cause, search if you need to.

Raising the shift RPM points with sport mode overcomes some problem with the valving and eliminates the hard shifting.
Vector

 

Thanks for the info. Will try it. Do you think a fluid change is worth trying?

 

I would definitely change the fluid.

 

+1 on the fluid change, but the problem is wear on one of the valves which can be fixed if you want to drop the pan and replace the valve assembly.

Putting it in sport mode worked for me though.

Vector

 

The electrical connector is a known problem -- simple fix .. this can cause all kinds of strange issues.

This should be check regardless of miles/ operation. Do a search -- you will find a lot of information. Always use the OE part.

Fluid changes normally don't fix problems .... Lots of these run to 200k with the original fluid.

I have owned 6 cars with basically the same box and never touched them -- 3 MB's 2 Jags and my Porsche -- two went over 200k

 

Just got a quote from a dealer today on changing the transmission oil and pan/filter plus bolts. $1299.12 for my 2005 XJR. He said that was a ball park as it might cost more depending on "what they found".

I will wait for warmer weather and do it myself and I will use the same technique I used on my 2006 Dodge Dakota as soon as I find out which cooler line pumps fluid back in to the transmission from the cooler.

I want to do a complete flush.

 

This thread is about the Mercedes transmission. Your car has a ZF 6HP26 transmission. For more info regarding your car, refer to the X350/X358 forum.

 

Yes you are correct my car has the ZF 6HP26 transmission ...which is a Mercedes transmission.

 

No, it is a ZF transmission. Earlier XJR's have the Mercedes 722.6.

 

"Yes you are correct my car has the ZF 6HP26 transmission ...which is a Mercedes transmission."

Can you seriously not distinguish between a transmission MADE by Mercedes, and one that's used in them?

ZF 6HP26 is made by ZF. Used in Mercedes, and many others. If you're going to say it's a Mercedes transmission, you might as well say it's a Jaguar, Hyundai, Bentley, or Land Rover transmission.

Mercedes W5A580 is made by Mercedes.

 

Ok I stand corrected. I must have mis-read a posting somewhere else in the Forum. It probably said that Mercedes "used" this transmission.