Sudden Transmission issue, slipping

[Chad800xt]

Hello everyone,
I am new to the forum but have been reading posts for a long time, this is my second x5 and this forum has helped me many times already...
My issue...
I have a zf-5hp24 in a 2002 X5 4.4i 160km's, only had the vehicle for a month and don't know the maintenance history. Been driving and shifting great up until a couple days ago... First odd thing I noticed was A brief shutter between shifts during soft acceleration, I'm thinking 2-3 gears, only lasted for a second as I let off the gas and then it resumed normally, did this twice on 2 seperate occasions. Next day I got in the car and when I put it in park I noticed a delay before it engaged, was longer than normal, maybe 3 sec. After that everything was normal. Next day, after drifting about 5 mins, make the corner and go to accelerate and the trans slips, the rpms jump about a 1000 and it lurches into gear and forward... Resumes driving as normal FOR 5 min. Then she does it again, this time with a squeel when it grabbed the gear, does it on the very next soft acceleration and "FAIL SAFE MODE" appears. The trans goes to 4th or 5th and I limp it a couple kms home. I left it alone for the night and this morning I investigated further, starts with no fail safe mode, CPU throws no codes and it appears to shift ok under soft accel, if I punch it a little I can tell it's slipping a little and makes a bit of a squeel noise. Only drove it around the block and now it's parked until I can resolve this issue. I am very mechanically inclined but have little knowledge of the internals of automatic transmissions and even less about the ZF ones, any input would be greatly appreciated.
Thanks, Chad.

[Doru]

I would do an ATF change.
I had almost similar experience with the e39 (also ZF tranny, but only 5 speed)
After I did the ATF change, it never re-occurred. This was done in fall 2008. No issues since.

[upallnight]

Most likely one of the o-ring in one of the drum has failed.

[Chad800xt]

Originally Posted by Doru

I would do an ATF change.
I had almost similar experience with the e39 (also ZF tranny, but only 5 speed)
After I did the ATF change, it never re-occurred. This was done in fall 2008. No issues since.

Thanks for the reply,
I'm worried that I will waste my money on new fluid/filter and have the same issue only to discard the fluid. I would love for this to be my answer but my gut feeling is something worse...

[Chad800xt]

Originally Posted by upallnight

Most likely one of the o-ring in one of the drum has failed.

After my many hours of reading this is what I am leaning towards...

I played with it some more today, when it's cold no issue... After 20 minutes of idle slips like crazy. It is something mechanical, but what ? Do I attempt the repair myself or pay the big bucks for a complete overhaul I may not totally need. Money don't grow on trees but I need a reliable vehicle for the wife, what to do.....

[JCL]

Have you rebuilt transmissions before, or done similar jobs? If so, order the manual from CTSC and open it up. But if you don't know what you are looking for, it won't necessarily be cheaper than paying for the repair.

[upallnight]

O-ring are used to seal the fluid passage way and create pressure for the transmission to work as designed. When an o-ring fail that mean the pressure can not be maintained and that is why the trans is slipping. It may not slip when the trans is cold because the ATF is thicker when it is cold, but as the trans heats up the fluid thins out and the pressure can not be maintain.

[Chad800xt]

Originally Posted by JCL

Have you rebuilt transmissions before, or done similar jobs? If so, order the manual from CTSC and open it up. But if you don't know what you are looking for, it won't necessarily be cheaper than paying for the repair.

Never rebuilt a transmission, have installed shift kits on domestic units and have been turning wrenches my whole life. I have looked over the schematics and browsed some other forums looking at the rebuild process, a little intimidating for sure...

I called one shop I have used years ago, they quoted me $2400 - $2800 for a rebuild if I take the trans in to them. My hesitation is that there gonna replace everything weather it needs it or not.

[upallnight]

Originally Posted by Chad800xt

Never rebuilt a transmission, have installed shift kits on domestic units and have been turning wrenches my whole life. I have looked over the schematics and browsed some other forums looking at the rebuild process, a little intimidating for sure...

I called one shop I have used years ago, they quoted me $2400 - $2800 for a rebuild if I take the trans in to them. My hesitation is that there gonna replace everything weather it needs it or not.

Since they will have to tear it apart, wouldn't it be better to replace all the parts that could wear and not just the parts that failed? Most of the cost is labor and they will need to buy a rebuild kit anyway. False economy replacing just the failed parts instead of doing a complete rebuild.

As a shop I wouldn't offer a warranty if the customer only wanted to replace what was broken and not do a complete rebuild.

[JCL]

Originally Posted by Chad800xt

Never rebuilt a transmission, have installed shift kits on domestic units and have been turning wrenches my whole life. I have looked over the schematics and browsed some other forums looking at the rebuild process, a little intimidating for sure...

I called one shop I have used years ago, they quoted me $2400 - $2800 for a rebuild if I take the trans in to them. My hesitation is that they're gonna replace everything whether it needs it or not.

They are going to buy a standard ZF parts kit that includes all the seals, gaskets, springs, etc. The manual will give the specs for things like clutch plate thickness, etc. They aren't going to replace parts that meet the reusability guidelines, it will just slow things down and tie up a bay or workbench. They may need a bearing or two. The failure is likely an o-ring as mentioned above, or an actuator, or a seal, hydraulic in nature and thus leaking dependent on fluid temperature.

I haven't gone into a ZF transmission (Chrysler, Ford, GM, Born Warner, yes) but I would do it as a challenge, it could be a fun job. But only if I had a good place to work on it, and lots of time. Lacking either of those, I would have a shop tear it down.