ZF 5HP24 Transmission Help

[E90twinsnail]

his is the THIRD time I have the transmission (ZF 5HP24) out of my 02’ E53 X5 4.4 and it is still not working correctly.  I’m at a point of pure frustration dealing with the trans and I’m not really sure where to go from here.  

The first time I pulled the trans I replaced the torque converter and replaced the pressure regulator valve with the upgraded one from TransGo (to address issues with torque converter lock-up codes as well as harsh shifting and going into fail-safe).  After getting the trans back in was still having problems now with a new series of codes.  When selecting a forward gear (reverse functioned normally) there was a slight delay and then it "clunks" into gear.  If by some luck it doesn't immediately go into trans safe mode by then it will shift harshly with the engine freewheeling/revving up before hunting for the next gear.  The codes I was getting were P0750 and P0751 and seem to indicate an issue with "shift solenoid A."  After doing a lot of research I became convinced it was an issue with the A-Clutch drum.

The second time I pulled the trans I found that the O-ring seal between the A and B clutch drum was split which seemed to explain all the remaining symptoms I was having.  I got the trans back in and went back for a test drive and noticed that it was no longer banging into gear when I engaged drive and was very hopeful that it was finally fixed.  However, before I even got out of the driveway it went into fail-safe and I was absolutely devastated.  It was showing the P0751 “Shift solenoid A stuck off” code again so I crawled back under the car to recheck the electrical connections and trans fluid level.  Before I set off again, I reset trans adaptations with INPA hoping it may be a TCM learning issue.  This time I actually got to witness the transmission shift and was astonished to see that it was behaving absolutely normally.  The shifts were smooth and quick with no free wheeling or hunting for gears.  I was really hopeful but after 2 miles of my test drive the dreaded fail-safe signaled itself across the dash even though it was otherwise behaving normally.

I now have the trans out a THIRD time and have dug a bit deeper by disassembly the A and B clutch assemblies.  I checked all their various seals expecting another leak, but everything looks pristine and undamaged.  I used INPA to pull up the error history and noticed a low voltage error.  Since the car has been sitting for so long my battery no longer holds a charge for more than a day or two without use and I usually have to jump start it before each test drive.  I’m beginning to suspect that the issue may be a bad battery, but I would think when it's running it would have more than sufficient voltage to not effect function of the trans. 

I’m really at a loss here and don’t want to have to put the trans back in this car again until I’m certain I fixed the problem.  Unfortunately, I’m out of ideas and I’m hoping that the collective knowledge of the forum may help me in this fiasco. 

Currently I feel doomed to be spending the rest of my life just pulling the trans and putting it back in again…

[Greydog]

Morning Daniel

Welcome to the Forum

Wow what a Saga, on the plus side the forum has gained a trans specialist😁.

If your battery is on its way out that is where I would start X5's are power consumers extraordinaire. Battery voltage should be minimum 12.5 to 13.00v engine off, 13.00 to 14.5v engine running. Any voltages below 12.5v engine running will throw all sorts of spurious codes "Trans Fail Safe", "Susp Inactive" being the favorite 2 when charging is low.

So as a Battery weighs way less than the trans that would be may starting point, first get the battery checked also check the alternator out put should be around 14.4 v. I suspect the battery is dead so I personally would bite the bullet and change it. 

Good Luck

Dave