Proper permanent fix for 5hp24
#1
12-24-2016, 10:33 PM
Proper permanent fix for 5hp24
The infamous 5hp24 failure bit many a jaguar and BMW owner. Mine seems to have lost ability to move forward, which is typically "A" clutch drum failure. I have read many references to the valve body wear being the root cause of the problem. The main pressure regulator malfucntions, presumably due to the bore being worn out, fluid pressure spikes cause the trans to slam into gear, which in turn causes the drum to fail. This explanation makes perfect sense to me from an engineering standpoint.
I have seen the following remedies to the valve body issue:
1. Oversized piston (ream the bore oversize, replace the piston with a larger one)
2. Revised (possibly oversized if the bore is worn) piston. I would be curious to know how the revised one is different and why it will work better.
3. Aftermarket kit with a different pressure regulator piston (Transgo 5hp24-pr). The piston seems to have some o-rings. If the bore is worn and/or scored I doubt it will work. If the bore is not problematic, the transmission would probably be in good working condition. Otherwise the failure is caused by something other than pressure regulator malfunction.
4. Replacement valve body from ZF. If the original one lasted roughly 100K, so will this one? Has anyone gone this route, and how expensive is this option?
I am thinking whether boring the hole oversize and pressing in a brass sleeve is an option. If the brass alloy is chosen correctly, it will resist wear, scoring and galling a lot better than a "bare" aluminum bore. A nicasil coated bore would have lasted forever, but ZF doesn't do nicasil in the valve body bores AFAIK.
Any other advice on rebuilding the 5hp24 myself would be greatly appreciated. Ericsson is a highly reputable shop that will certainly do a great job rebuilding the transmission. I am not planning to send the transmission to them, other than may be for testing the finished unit. For me the point of the exercise is learning how to fix the darn thing.
I am kind'a surprised to read about all the shop comebacks with 5ph24. The transmission does not look all that complicated. The valve body seems to be an 'economy' design, but if it fails at 100K it should fail after another 100K if properly rebuilt. I am guessing that the stumbling block for many rebuilders is actually doing exactly what the manual prescribes. As in, if the manual tells you to measure something, you really should do it. Not all parts are the same from the factory, and they also wear over time.
I have seen the following remedies to the valve body issue:
1. Oversized piston (ream the bore oversize, replace the piston with a larger one)
2. Revised (possibly oversized if the bore is worn) piston. I would be curious to know how the revised one is different and why it will work better.
3. Aftermarket kit with a different pressure regulator piston (Transgo 5hp24-pr). The piston seems to have some o-rings. If the bore is worn and/or scored I doubt it will work. If the bore is not problematic, the transmission would probably be in good working condition. Otherwise the failure is caused by something other than pressure regulator malfunction.
4. Replacement valve body from ZF. If the original one lasted roughly 100K, so will this one? Has anyone gone this route, and how expensive is this option?
I am thinking whether boring the hole oversize and pressing in a brass sleeve is an option. If the brass alloy is chosen correctly, it will resist wear, scoring and galling a lot better than a "bare" aluminum bore. A nicasil coated bore would have lasted forever, but ZF doesn't do nicasil in the valve body bores AFAIK.
Any other advice on rebuilding the 5hp24 myself would be greatly appreciated. Ericsson is a highly reputable shop that will certainly do a great job rebuilding the transmission. I am not planning to send the transmission to them, other than may be for testing the finished unit. For me the point of the exercise is learning how to fix the darn thing.
I am kind'a surprised to read about all the shop comebacks with 5ph24. The transmission does not look all that complicated. The valve body seems to be an 'economy' design, but if it fails at 100K it should fail after another 100K if properly rebuilt. I am guessing that the stumbling block for many rebuilders is actually doing exactly what the manual prescribes. As in, if the manual tells you to measure something, you really should do it. Not all parts are the same from the factory, and they also wear over time.