ZF 3HP22 - goes then stops after 5 mins

[garyinwestoz]

Ive started to dismantle my other 3HP22 cause it has a very sluggish reverse gear.

Well blow me - took a photo of the 3 pressure cups

and they are different to above.

overall


detai



bottom right is inverted (ie cup down) near No 17 on drawing

[Lock]

Gary, I've done that too - taken out the valve body, cleaned all of the sand and muck out, replaced all the gaskets and reassembled, and it didn't really change much unfortunately (there's a post here somewhere about it). I had flaring from 1-2nd, then lost 2nd entirely due to basically dislodging years of muck. If I had to do it again - I'd take the trans out, clean it all and rebuild because my blockages were in the casing itself, in the pistons and galleys right in the middle of everything. It sounds like something might be clogging your reverse actuators, but hard to say.
Like you I found the AussieFrogs forum and studied the manual, and like you also noticed that the 4HP22 is just the 3HP22 with extra bits so it's a at least helpful as a reference and there's more info out there for them. Given the gap in the instrument cluster between PRN-D21 I feel like BMW were considering putting the 4HP22 into the e12 and never did.
Also it seems year after year there are minor changes and the information about which year needs what check balls and cups and layouts is mostly gone now.
Not to say it's impossible, but you might need to dig into it further. Good luck.

[garyinwestoz]

The otherday, I did another test drive - initially went okay in 1st for about 30 secs, then it seem to obviously no have enough drive - wouldn't change up a gear - just slow an steady in 1st. Reverse worked fine now!

I double check fluid - seem low (nothing on dip stick) added another 1 ltr of fluid - made no difference, no forward drive at all now - have I added too much fluid now?

I read somewhere that putting in too much fluid, clauses too high a pressure for the pump, which then can potentially damage seals.

Maybe I'll drain and refill

or maybe this box is cactus afterall!