We've been having some issues with the transmission in the '04 XJ8. After replacing a sensor that "might" fix the issue (it didn't) the transmission light was still on and the transmission would fail and go into limp home mode regularly. Most recently the mechanic said that he wants to try replacing the valve body. Does anyone know what this is or how much it costs?

Some random link I've pull out from Yahoo.

A Boy and his Jeep » Blog Archive » More AW4 Madness, Valve Body

That big chunk of maze looking thing is the valvebody.

I don't really see how the valvebody can fail physically other than something clogged up in the maze think.

I would really suggest use the correct fluid to fill the transmission using the correct method to make sure eliminating human error before commiting expensive unnecessary parts buying.

Just wanted you guys to make sure it is the correct fluid with the right property for the tranny to preform as expected as the sensor will only have a margin windows of slip it expected. Too much slip with incorrect fluid will heat up and send it limp mode I believe. Too little or too much fluid will overheat the tranny as well which will have the same consequense.

Also wondering how you know it's the transmission light? Does it said "transmission fault" at the message center or the amber light on the dash board?

The valve body casting can sometimes crack, so needs replacement. You don't need to replace the whole shebang.

Some info on the transmission... click on the ZF6HP26 link in the left column.

zf6hp26 illustration - Bing Images

The ZF 6HP26 has what is known as a 'mechatronics' (mechanical/electronics) valve body assy.
The failure can be mechanical and/or electronic!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

bob gauff

Which codes do you have ?

The TCM module is inside the transmission case, with a plug connection so it can get infor from the ECM etc. There is a seal on this that can fail and affect the inputs on the plug from corrosion. Something to check, maybe ?