I thought it would be wise to ask my question here since not everyone checks both XK8 and Xj8 forums.
I am considering changing the main pressure valve to the upgraded version, seeing as I have no indication of shifting delay and may not need a valve body rebuild.
What I would like to know is if it is necessary to remove the valve body, or can this be done in situ?

 

Why are you doing this and if you do why not look at the possibility of replacing the valve body ?

 

We have a recent thread here https://www.jaguarforums.com/forum/x...re-info-88369/ about the possibility to change the valve body and for sourcing a rebuilt unit.
On youtube I found a very nice video of changing it on 5HP24, I would do it instantly, no big deal but only benefits.

 

Gus, the BMW pdf, which supplied to the XK8 forum by red october on 1/17, gave me the impression that installing the upgraded valve at a cost of about $30 might extend the life of the valve body if it is not already worn. I had already watched the video that flay contributed, and agree that it is relatively easy. But that was done with the transmission on the bench, while I am wondering if an advantage would be gained by just changing the valve while doing a filter service.
What I don't know is whether or not the valve can be replaced without removing the valve body.

 

This white paper was posted on my page as reading material when I began doing research on why my drum failed and is believed to be accurate. I will ask ZF today when I call them as to the accuracy of this information. I have always been in favor of preventive maintenance and would have done what they suggested had I known prior to my failure, what I question is if the failure was immediate or over an extended period of time. I will ask and post that information when I call them.

Link to Clutch Drum Failure http://www.jagrepair.com/images/Auto...%20ZF5HP24.pdf

 

That's great, Gus. It looks like removing the valve body could be tricky with the trans. in the car, but anything that can be done to prevent the drum failure should be of interest to all owners of the 5HP24.

 

The ZF 5HP30 transmision on my old 1993 E34 BMW 540i started to misbehave at around 130,000 miles, with the delay in engaging 'D' & then later the sickly lurch when the engine was revved.

I researched the problem & came across the pressure regulating valve problem in the valve block body. As the gearbox had never been serviced, I had everything done at once-old fluid drained & sump pan removed, valve block removed & faulty valves replaced, new filter fitted & gearbox refilled with new oil, torque converter flushed as well.

The whole lot came to around $650 back in 2007, compared to a full gearbox rebuild cost of around $3500 & upwards if the forward clutch had fractured.

Of course, with an old high mileage gearbox there's no guarantee that damage hasn't already occurred anyway & the 'A' drum perhaps weakened. But as the valve block overhaul can be done with the gearbox sump removed, it doesn't massively increase the service cost if it's done at the same time as the old fluid is drained & a new filter fitted anyway.

For a gearbox fluid & filter change service, the old fluid will be drained & the sump pan removed anyway-so it's relatively easy then to also have the valve block removed & overhauled while it's easy to access. Then you've got an overhauled valve block & new filter/gearbox fluid all done in the 1 job to minimise doubling up on labour charges if you had the jobs done at separate intervals.

The ZF 5HP30 transmission on my old BMW was a beefed-up version of the 5HP24 & shared the same basic design-and design flaw...

 

I took mine out on friday after dropping the front lower VB, no gaskets on this piece, btw. I had no way to vacuum test it, but there were shiny metal deposits running out of the bore when I removed the plate. The deposits show me that there is wear in the bore. I had already broken an A drum once on this engine and installed the upgraded one about 20-30k ago. Seems like if you have nothing better to do, swapping a valve body rebuilt with the sonnax oversized PR valve would be the way to go. Valve body swap is alot easier than the A-drum!

Also found a sticky #1 shift valve in the rear VB (did not remove this one from the car) put it all back together and the same slipping in 2nd gear symptoms persist, so now I'm installing my other transmission.

 

OK Jagnificent, just to double check, you are saying I can drop the front lower valve body seperately, and that is where the main pressure valve is located? That certainly is easier than removing the trans. and replacing the A- drum. Besides, it is obvious that replacing the drum without rebuilding the valve body is not good enough.

 

The valve block can be accessed on most autos once the sump pan is removed-it normally sits immersed in the transmission oil anyway & doesn't normally require the whole autobox to be removed to access & remove it.

 

Better to remove the whole valve body and to open it in halves on a table , away from the car. As I seen on other youtube , there are many small parts, springs and you don't want to do this if there is a risk of loosing parts or popping springs after opening it.

Anybody checked the prices for the rebuilt units on the links given by Jim? Do they sell to the public or dealers only?

 

This is the information I got from my source at ZF on the validity of the white paper http://www.jagrepair.com/images/Auto...%20ZF5HP24.pdf

“Hi Gus,
The info from ATSG is mostly correct. The main pressure valve will hang in its bore due to wear. Excessive pressure will cause the weakest link to break. Possible the D or G drum or both. The modified main pressure regulator will prevent this but only address part of the problem. Valve body wear is a problem with any transmission and must be addressed. What is ok today maybe tomorrows problem. All bores in all three housings of the ZF 5HP24 transmission should be inspected for wear. Best method is to run a right angle pick and run it through the bore. If it catches a step at the end of the valve travel the housing is bad and needs to be replaced. All housings are readily available through ZF parts distributers.”

I am gathering additional information on fluid replacement and a how to from ZF that I will be placing on my page.

I hope this helps!

 

That sounds like a somewhat partial yes for replacing the valve. I hardly expect ZF to say it will solve the problem, but seeing as I have a '97 and no indication of shifting lag, I think I will do so when I pull the pan to replace the filter next month.
Now that I know how to check the bore for wear I will also do that, and replace the valve body if necessary.
Thanks for providing this info, Gus.

 

There are no worries about losing springs or anything during removal of the front lower VB. Its when you remove the plate that covers the valves that you have to watch out for spring tension. The one covering the PR valve (the biggest one) has the most tension, btw. I used channel locks to hold the plate down while I started the little bolts. If the bore is worn, i would suspect the usual replacement valve would not make a difference, but if you already have it and already have the VB down, why not toss it in anyway!?

EDIT: Just read you have 97. You might possibly have some checkballs on top of your VB, just dont remove them without making sure of where they go and dont turn the VB upside down until you have identified them all! Good luck!