Okay so I know this might be sacrilege and I apologize for posting here but there seems to be many people on this forum who are very intelligent when it comes to the transmission on these cars!

I have a 2003 BMW 540i, it has the ZF HP-24 gearbox. The car has an issue where when slowing down, and going under 15 mph it will clunk from 3rd to 2nd. It will also bang when going from 2nd to 1st. The strange thing is that when it does this bang from 2nd to 1st it will stop completely as if something in the transmission is holding the car still, If I press the gas, I move forward and all is well, if I slow down again to about 5 mph or less the transmission will clunk and the car comes to a stop again, as if there is a braking force inside the transmission. If I shift the vehicle into sport mode or semi auto mode then the 'brake' releases and the car rolls naturally forward as an automatic should.

This has been going on for a few months, I have recently replaced the transmission lines (busted quick connects), transmission filter to BMW OEM, Transmission tstat (Leaking), and even the pressure regulator valve for the upgraded transgo unit. The car has had several cycles of new fluid and has brand new Maxlife atf fluid in it right now.

The problem that I have with the car is something I believe that is very similar to what this guy says near the very end of this video
Here is a video that I have made describing the problem and demonstrating what happens
I think I have it narrowed down to 4 possible scenarios,

1. something wrong with valvebody ( The bores are worn out....? Maybe a crack like Gary F talks about?)
2. something wrong with torque converter
3. something wrong with shift linkage?? (I saw a somewhat similar issue get discussed hear on the forums and this was the solution.)
4. just plain worn out internals and transmission needs a full rebuild
Again sorry to post this in the Jaguar Forums.. but our cars share the same gearbox and it seems like the jaguar enthusiasts are a little more proactive with their gearbox maintenance.

 

This is a very popular gearbox amongst many manufacturers...you found the right guy with Gary. Where are you located?...Gary is in NJ and you can email him through YouTube. Just go to his site, and under About to reveal it.
I would send him your video as well...but I would anticipate it having to be dropped and broken down to determine that issue.

I included a PDF of a parts breakdown of the trans.

 

Update: I just spoke with a member with this identical description you have in your video and he had a cracked valve body.

 

I dealt with a cracked VB once and it occurred because the engine overheated or someone power braked it way too long to heat up the transmission fluid. If you or any other owner(s) had experienced overheating, then that could be your problem.

 

Hi there if it is a crack in the upper section of the valve body you'll need the casting / part #
If you can get the whole serial and model # off the Transmission should be by the shift lever bracket. Then call Eriksson's industries. In Ct. 1800 388 4418
good guys there Matt and Scott.

Thats usually what happens.
bottom center across the casting /part number.
hope this helps.

jay