A904 PISTON INSTALL HELP!

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joshua dewitt

joshua dewitt

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STARTED REBUILDING MY 1973 A904 TRANSMISISON, GOT TO THE BEVEAL SPRING REMOVED CLUTCHES, AND PISTON FELL OUT, SEALS SHOT.... NOW I HAVE THE NEW LIP SEALS ON, AND LOTS ON TRANSGELL WITH ATF. BUT CAN NOT GET THE PISTON TO WORK IN CAREFULLY, I DON'T WANT TO FORCE IT OR TEAR THE SEALS, BEEN TRYING TO USE MY MINI PICKS, AND FEELER GAUGES, BUT AFFRAID OF TEARING THEM. IS THERE A SPECAIL TOOL I CAN BY YO DO THIS? OR IS THERE ANOTHER TRICK I'M MISSING? THE REST IS MOSTLY TOGHTER. JUST NEEDING A HELPING HAND/GUIDENCE TO THIS STEP,. THANKS
ON VACTION, TRYING TO GET IT DONE.
 
A band around the seal and then put it in the freezer for 20 min helps sometimes.
I always used a flat blade like a feeler gauge .010 and tapered it so the part that actually goes between the drum and the piston was a 1/4 wide.
Polish it nice and smooth on the edges.

Sometimes putting a little down pressure and working the piston around in circles does it also.
Not turning the piston, but just hold it solid and work it around in a flat circle while gently holding solid down pressure.
You can air check it to make sure it didn't fold the seal.
 
that is exactly what I have been doing, isn't working... except the freezer thing, might try that. what bad around the seal are you talking about?
 
well I figured out it is the forward drum/ piton giving me trouble. I took a break from it. never had this much trouble before with any lip seals, going to need another set . rough on edges now on outer seal. not sure why so hard to get in. is there any Transmission builders out here that knows if there is a lip seal protector/installer like used in gm transmissions?
 
TrailBeast said:
I always used a flat blade like a feeler gauge .010 and tapered it so the part that actually goes between the drum and the piston was a 1/4 wide.
Polish it nice and smooth on the edges.

Sometimes putting a little down pressure and working the piston around in circles does it also.
Not turning the piston, but just hold it solid and work it around in a flat circle while gently holding solid down pressure.
You can air check it to make sure it didn't fold the seal.
Click to expand...

That's how I've been doing them for 35 yrs. and it always works for me. Just be patient and don't force it
 
I know, just the inner lip seal will go in tried with out the utter installed. then tried the outer with out the inner installed wont go in. I'm wondering if the seal may be wrong? I know they are a pain in the ***. I do 700r4/ 4l60e/ 4l80e, and 6l80/90e. 67t70. 6t45, transmission for general motors dealership. just never had this much trouble before with one, I was wondering if a bad designed seal? or was a possible trick I didn't know of, or a special lip seal sleeve installer tool that is used like the gm's? never done a a904 before. it is easy enough, just except for this piston that is kicking my ***. and of course the old one tore coming off.
 
joshua dewitt said:
I know, just the inner lip seal will go in tried with out the utter installed. then tried the outer with out the inner installed wont go in. I'm wondering if the seal may be wrong? I know they are a pain in the ***. I do 700r4/ 4l60e/ 4l80e, and 6l80/90e. 67t70. 6t45, transmission for general motors dealership. just never had this much trouble before with one, I was wondering if a bad designed seal? or was a possible trick I didn't know of, or a special lip seal sleeve installer tool that is used like the gm's? never done a a904 before. it is easy enough, just except for this piston that is kicking my ***. and of course the old one tore coming off.
Click to expand...

Did you try putting a band around it and sticking it in the freezer?
I don't know of any tool for that one because of how the piston lip extends out over where the seal is.
 
joshua dewitt said:
I know, just the inner lip seal will go in tried with out the utter installed. then tried the outer with out the inner installed wont go in. I'm wondering if the seal may be wrong? I know they are a pain in the ***. I do 700r4/ 4l60e/ 4l80e, and 6l80/90e. 67t70. 6t45, transmission for general motors dealership. just never had this much trouble before with one, I was wondering if a bad designed seal? or was a possible trick I didn't know of, or a special lip seal sleeve installer tool that is used like the gm's? never done a a904 before. it is easy enough, just except for this piston that is kicking my ***. and of course the old one tore coming off.
Click to expand...
I've been making videos of my 904 overhaul, and I found a segment where I compared all three different lip seals that came in my kit. It was easy for me to differentiate between the outer piston seal for the front clutch vs the outer piston seal for the rear clutch once I had them all out beside each other. Did you not save the old lip seals?

Go to 32:00 and I have all three side by side, sorry for the poor lighting. The one on the far right is the one I did NOT use in either place. I know this is the front clutch segment but I didn't show the rear clutch piston seal clearly in that segment.

 
already found that video online you tub.. thanks.....
but trail beast, that freezer trick worked!!!! I left in overnight with some masking tape around the outer seal, , removed tape lubed up, slid right in. now once assembled I will air check and verify that the seals still works or is damaged. is the only way to air check the clutch packs assembled in the transmission though the case ports? or can you blow gun check on beck like other units?
 
you can assemble the front clutch pac and rear clutch pac with the pump...and air check it them
 
Yep, just some electrical tape around the seal to compress it and into the freezer..
 
70aarcuda said:
you can assemble the front clutch pac and rear clutch pac with the pump...and air check it them
Click to expand...
That's how I do it. First flip the pump over and clamp it in your vice using soft jaws, then stack the clutch packs in order on the pump & inject 30-35 psi air into the pump ports that lead to the respective clutch packs. This also checks to make sure the reaction shaft seals are sealing up. One Note is to hold on to the clutch packs when you inject the air because they will want to jump up and off the pump
 
fishy68 said:
That's how I do it. First flip the pump over and clamp it in your vice using soft jaws, then stack the clutch packs in order on the pump & inject 30-35 psi air into the pump ports that lead to the respective clutch packs. This also checks to make sure the reaction shaft seals are sealing up. One Note is to hold on to the clutch packs when you inject the air because they will want to jump up and off the pump
Click to expand...
 
just thought about it on way to work this am. I get the pump, using the retain shat to seal against the piston housings.so do you know which fees holes in the pump housing feed these when air checking? ats service manual pretty vague, no pics on this , or showing to air check your work. , also, I've since plug taped the pump vent off, to avoid leaky seal syndrome. I have since vent the case in the fornt above the band and at the rear of the housing just ahead of the tail shaft, have a dual hose vent system form a 4l60e/transfercase set upon it to one vent.
 
4 ports on the pump backside. If you have the ports on your right stacked as mentioned, the furthest away is the Direct, then forward, then converter charge, then return. You can also insert the whole assembly into a converter to test it, too.
Never had to use the freezer method, just patience and a seal installer, which looks like a feeler gauge with a plastic handle.
 
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i tried it tonight... according to FRED S... I went with the four ports on pump with clutch housing installed and this is what I got. see pics.... I know some air bleeds bypasses though the pump housing, and can feel the air tat the Big O ring around the pump housing where this is larger hole area... the farthest right did nothing, the next did the rear/forward
pition air check.png
clutch, applied ok, nest left blows fluid out the next left hole wit being in the converter? see pic...
 
I know this is not right any thoughts? and I marked the pump housing halves before I took apart to inspect for damage or excessive wear. so I know they are tighter right.
 
if all you hear is air on the first port, then its leaking. Are you using metal or viton seals on the stator for the direct drum?

Pack them with assembly goo heavily. Pull the drum assembly off and shoot air into the port and see where the air is coming out on the pump stator. Should be a hole between the 2 sealing rings. If its there, then issue has to be the seal. It is easy to roll one.
 
using the metal sealing rings, I haven't changed to the new ones yet, will try the new rings 1st. so you think the seals for the reaction shaft are not sealing, that was what I was thinking. now my reaction shaft has some light wear grooving in it, but that rides against the bushings in the housings. not seals. do you thin k I should use the split Teflon seals, or stick with new metal pup seals?, will look at it tomorrow night, too late tight now. thanks for the info.
 
red s, would you have any pics of the rings you are talking about I may have rolled? I took the drums off, and air checked again, they both apply separately, but a lot of air coming form the outer pump housing where large o ring goes, is this normal? will it seal once in the case? not sure, can not find any info with pic or video showing air checks with being apart before assembly.
 
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