Replaced automatic transmission

anthony · Post by **anthony** » Tue May 22, 2012 9:49 pm

I replaced the 4HP22 automatic transmission on my 735 with another from a p n p.

It is not working. I mean absolutely nothing, no reverse no forward.

In the process, the torque converter was drained of transmission fluid, and was installed dry.

Co-worker said I should have pre-filled the torque converter. I looked it up and many said not necessary in general. I was unable to find any BMW info. One thread supported the idea the pump is broken.

The best out come would be to gain access to torque converter and fill replace. This would be a lot of work to just hope it works. I would rather replace the transmission and torque converter.

Does anyone have any experience with this?

labimmer · Post by **labimmer** » Wed May 23, 2012 9:52 am

I have a transmission like that if you need fron 735i 1986

On 05/22/12, anthony <ketcham99@comcast.net> wrote:

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I replaced the 4HP22 automatic transmission on my 735 with another from a p n p.It is not working. I mean absolutely nothing, no reverse no forward.In the process, the torque converter was drained of transmission fluid, and was installed dry.Co-worker said I should have pre-filled the torque converter. I looked it up and many said not necessary in general. I was unable to find any BMW info. One thread supported the idea the pump is broken.The best out come would be to gain access to torque converter and fill replace. This would be a lot of work to just hope it works. I would rather replace the transmission and torque converter.Does anyone have any experience with this?
Anthony1980 528i 3.5 M30B35 motronic 1.3
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anthony · Post by **anthony** » Wed May 23, 2012 2:23 pm

Thank you.

I have an extra transmission and converter. The amount of work to do a complete swap is more work than just separating the transmission from the engine and adding fluid to the converter.

I was/am hoping for someone to say " just pre-fill the the converter and you will be fine"

Mike W. · Post by **Mike W.** » Wed May 23, 2012 9:03 pm

I doubt you could drain it well enough to cause problems once it's been filled. The infamous "A" clutch pack failure only affects forward gears, so that's not the problem. How certain are you the torque convertor was properly seated when you installed the tranny? I've seen more than one instance on Mye28 where someone didn't have it installed properly, bolted up the tranny to the engine and crushed the oil pump, which is right behind the torque convertor.

The 4HP22 is a good tranny aside from the above quirk, but it still came out of an almost 30 year old car in a junkyard. Any guess why it was there? Smog is a common one, but with the buyback programs a lot of those just get crushed and don't go to the yard.