Trans help needed
 

heres the car info, 1992 sl500, 722.3 transmission 100k miles
last year the trans was slow going into reverse, this winter i changed the fluid
{bad idea} it went backwards three times after that reverse was gone.
after reading about the b3 piston seal failures and accompanying friction plate wearing i decided to drop the trans , replace the seal and frictions, and reinstall.
upon removing trans and dissasembling the seal was ripped and frictions were toast. new seals new frictions and back up.{why not rebuild the whole thing? the rest was in really good shape, and while going that deep for the b3 didn't scare me, the thought of delving all the way was more than i really wanted to commit to. i could have brought it and had a shop do it, but this gem of a car is starting to exceed the money to enjoyment factor, and i don't wish to marry it !}trans back in, start it up, and a loud thumping banging noise commences, then goes away after a few seconds...put it in the gears and you can feel it go into gear but it doesnt move unless you reaaalyy rev the car{best way to describe is if you have ever had a drag car with a high stall converter, similar} well i thought,I didnt engage the converter properly, it bashed the pump gear and was moving from the fluid being pumped from the secondary pump..you could also hear fluid gurgling when you shut the car off.
so out comes the trans pull the pump, dissasemble, and nothing...no marks of something hitting nothing broke, zero, not oneclue as to what went wrong...
do these cars have to prime the system? it ran for probably a minute, then i had tried it again with the same result{didnt let it run much more than that do to fear of something beating itself to death....} now without a clear cut screw up on my part i have picked up a trans from a 92 with a 115k on it, ran when they pulled it...my theory was to find a broken pump gear, swap the pump from the boneyard unit and reassemble and install my original unit..but now without something obvious im thinking of putting the used unit in and getting it mobile...unless you guys have something that i can look for?? thanks for any ideas...

For sure something happened in the front pump area when the housing was removed.

DID you have the pump apart? IF so then possibly the outer rotor gear is installed back wards

Didn't take pump apart , past replacing the b3 seals,
Took it all the way apart yesterday as I couldn't believe the gear didn't break.. Was hoping to see it damaged so I would have my problem...Not even a scratch on it....

trans update
 

long story short, not finding anything wrong, I picked up a known good used trans, installed it, and same thing! massive slippage .....same..i mean the same symptoms as the other trans...i looked up the converter depth measurement.. ins in spec, i dont get it i need a idea where to go from here....thanks for any input...scott

here is a update of things I have checked and or found...
flexplate is good , not broken, did have the converter bolted to the flexplate, converter seated to correct depth per factory specs, propeller shaft flex discs in good shape, driveshaft segments meshed and connected, trans fluid to correct level, shift rod adjusted correctly{never removed past removing it from transmission lever, new vacuum line on modulator....so I'm lost....only thought as I write this is could a piece of debris could have clogged a cooler line causing this? have not been out to the garage to check this ,probably not until monday night.

Did you replace the torque cobnverter too? That could be your culprit (but don't ask me how it's broken).

I used the converter that came with the used transmission,
2 transmissions different converters, same result,
Ive worked on cars all my life and am baffled by this one!
I'm going to blow out the cooler lines to check for blockage, check the frt pimp assy, reseat converter, make a stop so It cannot move while being reassembled, put it in and try it... If it moves.. Great! If it doesn't, I'm pulling the plug on this car and dumping it not running, if it doesn't sell, it gets donated and I'll take what I can for a write off, not like these cars are worth much, and certainly not worth this much hassle...

This sounds like it has to be something basic. Now if the cooler line was clogged, that might also prevent you from getting a complete fill, right? How many quarts did you need, full is somewhere around 9 right? How about the vacuum modulator, I don't know if it could cause that much slippage, but worth a check. I think pulling the vacuum hose results in no modulation (hard shifting).

did you 'fill' the b3 after you replaced the friction/clutches? hope you didnt try it dry that may be your culprate

Nope, didn't fill the b3! Didn't think of that ,
But it should not have made a difference with the used transmission.... But good point to consider...

ok, here's a bolt by bolt update! the used trans i picked up looked like it had been apart before, possibly indicating it to be rebuilt at some point.
after removing the frt pump to look at the gear and check the insides out it looks as if it was done fairly recently! frictions are like new as are the seals, very supple no brittleness! the frt pump gears are not damaged, the cooler lines are not blocked, so besides having a fairly fresh trans{ which yard drove in the donor car} I still have nothing to go on as to why my original trans and this one exhibit the same behavior of massive slippage in all gears....so I reseated the converter{measuring it just to make sure} and am putting it back up in the car...at least it will be the last time either way....

Update please. Also, was it the same modulator or was that replaced too?

Different modulators... Nothing new to report until I can get into the garage
Probably a few days....