I am having trouble getting a good seal on my 904 transmission with conventional gaskets, even after carefully reworking the stamped pan to make it flat. I have a reusable silicone gasket with embedded steel sleeves for my other car with a 727, but I can't seem to find the same type of gasket for my 904. Does anybody offer one?

Dealer has the reusable gasket P/N 4295875ac. Be sure the leak is from the gasket and not one of the common sites above the gasket.

Thanks guys. Mancini was about the only vendor I had not checked with. Good price too.

I will double check the source of the leak, but it seems to be on the side opposite the shift lever shaft. Not much over there to leak.

Dipstick tube is over on that side. Might want to replace the O ring

Already did before putting the engine/trans in the car. Will check again though.

clean it with the car wash wand then keep an eye on it & if need be can even spray some talcum power around it to make it easier to then spot a trail of tranny fluid. someone mentioned a good method of getting the power sprayed up there but I forgot what it was.

Using a good old fashion cork gasket I soak it in water remove it and after wire wheeling the pan I place it on with Mopar gasket i a can or spray high tack and no leaks period

I've found a few tubes cracked and leaking in the o-ring area, probably from people bending them during R&R's.

Sometimes the spot welds get torn on the tube bracket, also causing leaks.

The transmission was super clean and had all new seals on the dipstick tube and gear selector shaft when it was mated to the engine on the K-frame cart. I thought I had the pan nice and flat before installing a new gasket, but it leaked after installation in the body. Tightening the pan bolts only helped a little bit. I will take it off again (messy job) and install one of the reusable gaskets after tweaking the pan some more. If that does not work, I will have to get a new pan, probably a cast aluminum one to insure it is perfectly flat.

Supercuda and Evil Spirit nailed it. Despite putting a new O-ring around the tube and carefully inserting it when the transmission was on the stand, it is leaking there now. I will now have to replace both the gasket and the O-ring while making another mess. I wish these pans had drain plugs!

Put a drain plug in now, or get a pan with a drain plug.

http://www.rockauto.com/en/moreinfo.php?pk=6685704&cc=1087589&jsn=868&jsn=868

^^ yes adding a drain plug is a good idea. put it on the side (rear if VB room) & just check before you drill that it ain't interferring with the VB. but dont neglect to after you drain the fluid to pull the pan & clean the bottom/change filter, that it is just to help you contain the sloshing fluid that would be there to be dealt with if there was no drain plug.

I think I found the reason for the leak and wanted to post it here for others that might have this problem. I found a suction pump and sucked the fluid up the fill tube so I did not have to remove the pan again. Then I unbolted the tube and tried to pull it up. It was jammed hard against the firewall and would not budge. I believe the stress caused the seal to leak. I was able to bend the mounting tab away and rotate the tube up and out. The transmission/engine combo came out of a Dodge van, and I believe the fill tube is bent different than an A body tube. I tweaked the bends and the tab and put it back in with a little clearance this time. I should know tomorrow if the leak is gone. The engine/transmission/K-frame combo was installed from below as a unit, and I did not notice the fill tube was crushed so hard against the firewall when the assembly was bolted in.