XK8 / XKR ( X100 ) 1996 - 2006

Transgo 5HP25 PR Valve

Old 09-05-2015, 11:00 AM
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Default Transgo 5HP25 PR Valve

In an attempt to avoid the common A drum failures on my 5HP24 gearbox, I decided to replace the ZF pressure regulating valve with the TRANSGO 5HP24 PR kit.

I ordered the valve and a new filter from the American Transmission Warehouse and was impressed with their prompt service. P&P is a bit hefty to the UK but it still worked out cheaper than any alternative I could find.

Two of the pan bolts were seized so that added a couple of hours to the job but they came out eventually. The front valve body was hung up on the locating pin and would not drop. In the end I looped a cable tie around the small cylindrical section that protrudes out of the front of the valve body and that allowed me to apply some downward force to free up the body. Worked a treat. Don't be tempted to use a pry bar in case it scratches the castings.

I can confirm there are no small *****, springs or other bits and pieces that come flying out if you are just dropping the front valve body (much to my relief).

The only other tips I can pass on are to use some cable ties to help with the closure of the retaining plate as you compress the valve springs on reassembly. Also, fasten the hand pump used for filling the gearbox onto a convenient strut with some cable ties (I like cable ties!). It made the job a lot easier. I am pretty sure I picked up that last tip from someone else on the forum so kudos to them.

The TRANSGO instructions are very clear and its all pretty straight forward. I reused my oil as it was replaced less than 10k miles ago according to the service record but I did have to top up with another 2 litres to get the correct fill. I noticed I have a slight leak around the output unit so I guess I will need to replace its oil seal at some point.

I have only done a few miles since the work, but all is well and I do think the gear changes are slightly smoother, not that they were bad before - probably the extra oil helped but who knows.

Hope that's helpful for someone.
The following 8 users liked this post by bamforp:
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Old 09-05-2015, 05:02 PM
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Does anyone have any information on improvements to the 5HP24 through the production run? This valve problem was known and documented for several years before the end of production of this model transmission.

Just wishing my '02 had been upgraded at some point in the production cycle.
Old 09-05-2015, 08:21 PM
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I thought the valve was upgraded in '01 and the A drum in '02. How many failures have been reported in the '02? I don't recall any.
Old 09-07-2015, 12:12 AM
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It is probably best to put a note in this post, that if the trans is already banging, on take off, it is useless to replace the PR valve, or valve body. Just use that money and put it towards another trans. Even if it does seem to work, it will probably only buy you 6 months or less, before bad things happen again......The voice of experience....Mike
Attached Thumbnails Transgo 5HP25 PR Valve-dscn0230.jpg  

Last edited by mrplow58; 09-07-2015 at 12:18 AM.
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Old 09-07-2015, 03:37 AM
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I think it is also worth noting that the ZF gearbox company (ZF Friedrichshafen AG) was founded by none other than Ferdinand von Zeppelin who also founded the Zeppelin Airship company (Luftschiffbau Zeppelin GmbH), who rather famously manufactured the Hindenburg.

You have been warned
Old 02-21-2019, 01:06 PM
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Default Transgo ZF5HP24 Upgraded Valve body

my Transmission is fine, but as I have no history, I was going to change the transmission fluid anyway. So naturally I thought I might as well upgrade the pressure regulator in the Valve Body. Not sure it’s time yet to overhaul the tranny
Old 02-21-2019, 01:40 PM
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I recently posted about this kit.

You can call up ZF in Chicago and get official info on the transmissions, very useful. Phone number in that thread.

BTW, they suggested changing the regulator and the valve body, not the A drum, a rebuild, or let it grenade.

Last edited by Ophitoxaemia; 02-21-2019 at 01:50 PM.
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