I got a pressure testing kit, but I can't find any info on how to test or what pressure to expect - Does anyone have any info on this?
In general I think there is enough pressure since all other gears but 1st are shifting fine. I'm thinking something got gunked up in the valve body or a solenoid is failing.

 

found some info:


the clutches and steels are fine (just checked and replaced). I'll gauge the pressure tonight and check if the pump is fine, but my best guess is that something in the valve body got massively gunked up.

 

did my pressure test - a very productive lunch break. I'm getting about 90psi at 750rpm and around 130 at 1500rpm (I'll blame the slightly lower than expected on a leaky gauge connection) - it was a bit scary to rev it up to 2000, but I guess it would go up to the 150psi.

Tested on all the gears - same results. My conclusion is that the pump is fine. Time to rip out the valve body...


and in case anyone is wondering where to attach the pressure gauge:

 

Good job on the testing and diagnosis! Let us know what you find.

 

So I got the valve body apart. Looks clean - shocking. The only odd thing, which im not sure how concerning this is, two of the solenoids are reading 26ohms. I've looked at a manual for transmission version E9 and it says those should be reading 30-35ohms. Another manual (edit: it's for modelEH) says those should be between 25-45ohms. Any thoughts on this.

On another hand the transmission rebuild manual i have for the hp22 says most jerky shifting would be caused by failing solenoid relays - I'm guessing those would be inside the trans ecu. So just for s&g i ordered a replacement ECU...

It's kind of annoying that the transmission ecu is not throwing any codes...

 

Doubtful the solenoids would read incorrect, solenoids usually fail open i.e. infinite resistance, very rarely will fail shorted i.e. zero resistance. Sounds like yours are normal. I guess it could be ECU but have never heard of one going bad except when the truck is flooded.

 

Hah, yes the ecu theory is a massive stretch, but quite honestly i'm kind of running out of ideas. Trans pump looks to be fine. I tested all the pistons when i had the transmission apart and they were all moving fine (at least with air pressure). I put in new clutches, even though the original ones were in spec. There is no blockage in the cooler or the lines.

I'd just buy a new trans if i could source it locally...

 

Holly crap - i put the cleaned out valve body back in and it's working. In fact it's crazy smooth. I can't even tell it's shifting. How is this even possible... that's insane...

Well, back on to replacing the third ps pump and the new knock the engine started producing...

 

Wow, weird but great news.

For the PS pump, I followed a couple of threads on this forum and rebuilt my own. It’s been working perfectly.

 

the only, marginally plausible explanation that I could maybe believe, comes from a BWM forum where they claim that over-torquing the valve body bolts can tweak the casting and make some of the shuttle valves stick... it would sort of line up with the jerky shifting scenario. Still, I torqued everything per the manual and there is only one torque setting so it's hard to mess that up....