2001 4.4 replacement trans, no reverse? Update, Fixed and driving!

[X53Jay4.8is]

Originally Posted by RToth

No stupid questions at all here, I'm grasping at straws myself as to why it's happening. At this point I believe I will end up pulling the trans because I can't make any sense of anything else. I disconnected the electrical to all the solenoids, which should be a direct path then to reverse and still no change.

As for wheels freewheeling in reverse, I can go from drive at idle speed with the wheels still rolling and brake just enough to allow it to go into reverse without stopping the wheels and the wheels still freely spin forward until the lack of power being applied to them stops them. Yes... I know it's not a good idea to go from drive to reverse, of course it can cause damage, at this point I'm not really worried about an idle speed drive to reverse drop with no load, was more curious to see if there was any resistance and there was not.

And you mentioned that when you put it in gear for Reverse you can hear the load against the engine correct? Then I am inclined to believe that the problem lies in the Transmission after all you have drive.

[RToth]

There is absolutely no doubt that the problem lies in the transmission, I never suspected anything else other then maybe a fault code which wouldn't matter. The question is where in the transmission does the problem lie, I am hoping it is something I can fix without dropping the trans and pulling it apart to find a destroyed F clutch piston, though I feel that is where this is headed.

[RToth]

Just remembered something.

When I pulled the transfer case off the input shaft for the transfer case came halfway out of the case. I was able to get it back in place as far as I could tell, any chance something happened when that shaft came out that could cause the issue?

[RToth]

Finally an update here!

I've been quite busy with work and family time, don't need the X5 until snow anyway so it's been on the back burner a bit. Finally had some time to dig into it again these last few days, I started to pull the valve body and did some more research and figured it was just a waste of time and decided to pull the whole trans. This time I had it out and on the bench in about three hours

Tearing it open was pretty straight forward, I have rebuilt around a dozen GM automatic transmissions so this wasn't all to unfamiliar. From some other posts / pictures on here it seems like this trans has been apart and at least partially rebuilt before, the A clutch drum assembly has the dimples that from what I understand is an updated part and was put in the newer transmissions built after this one. In any case, this A clutch assembly looks like new. The radial bearing that typically fails also looks excellent with no visible pitting or wear. Of course I found the smoking gun in the F clutch piston, completely destroyed.

Dimples on A clutch hub


Snap ring groove and the rest of the drum looks excellent with no cracking or wear.


Radial bearing in great shape


And of course the F clutch piston.... smoked. Only maybe 25% of the outer seal was in good shape with the rest of it completely gone, and the big chunk ripped out of the inner seal as well.











So... this is the plan. I am going to take the good A clutch hub assembly and install that in the original trans after I take that apart and make sure there is no damage to the F clutch piston in that one. It had reverse just fine but I would hate to be right there and not look at it then throw it together and have reverse go out in three months. Once I get that transmission in and all together and get the X5 on the road I will then fully rebuild the used trans that I purchased and used for parts.

[80stech]

Good Thread! I imagine then that you didn't have the updated piston ?

[RToth]

Nope, at least not originally by the serial number and if it did get it during a past rebuild it has failed.

[upallnight]

Thanks for coming back and updating this post. I would send a picture of the F clutch piston to the seller and explain to him that there's no way that the transmission he sold you had a working reverse. See if he is willing to reimburse you for some of the cost such as a rebuild kit for the trans.

[X53Jay4.8is]

Well at least you know that you were not going crazy and something minor was overlooked on the the install. Once again it is apparent that when we source a used transmission anything is game on what might be wrong on the inside. I have been there before so you are not the first to encounter such an outcome.

[upallnight]

Here's a link to a ZF5hp24 teardown trans by RRPhil (he has another user name on this forum but on thread #11 he identifies himself as RRPhil).

ZF 5HP24 teardown

[upallnight]

If it was my truck I would just rebuild the trans with the bad F clutch piston. At least you know what was the problem and a new F clutch piston and new reverse clutches and plates should get you reverse. You said that the trans have updated parts in it already. Plus the trans is already apart

You original trans goes into limp mode once it gets warm so you are assuming it's the A clutch assembly. Could be the A clutch assembly, but it could also be something else. Until you disassemble and inspect the original trans you don't know why it goes into limp mode.

Just my .02 cent.