TH400 Malfunction

[DRD57]

The first TH400, one that I have to admit I rebuilt, that I put in my roadster didn't work. It shuddered when in reverse and it wouldn't upshift from low gear.

I finally tore it back apart to attempt the repair. The outer seal ont the piston in this picture wa buggered up a bit and was obviously keeping the piston from moving freely.



Would this cause the problems I was having or might there be other problem areas?

How do I get this piston in the hole with out messing up the seal? There is a lip on the piston that prevents me from getting my homemade seal tool in there to help.

Thanks for any help and or advice.

Don

[Crosley.In.AZ]

you have problems some where else. That is the piston for 2nd gear only.

How ever........... the sealing rings on the cast iron piece seal up for 3rd and reverse . If that is leaking reverse will shudder. If it is loose in the case , it will leak.  Are the locating lugs for that center support worn so the center support can twist left to right in the case?  The cast iron piece OR the aluminum lugs in the case can be worn

There are 2 different thickness of the center support where it lugs into the case... The thinner center support uses a steel spacer ring that sits in the case between the case iron center support and aluminum of the case to prevent wear of the aluminum.  Did you have a left over thin snap ring after the rebuild?  It may have been left out before you got the tranny

Sealing rings broke?  Metal or teflon type rings?

Area where the sealing rings run in the drum  have grooves?

Cut lip seals in the drum? Curled over lip seals? Improperly installed like the 2nd gear piston lip seal?

Years ago there where thin metal tool box drawer release tools. You slid this tool into the drawer slide to release the drawer from the main tool box.  I use these to install lip seals daily.

No upshifts...... look at a stuck governor valve , stuck shift valves , wrong location of check balls, incorrect  valve body gaskets install

[Leon]

I use a little tool that has a loop of wire on the end.  Lube the seal with assembly lube (looks like blue vaselene) and the tool slides around without tearing the seal.