[n20ta2]

Just installed the pump in my th400 I'm building and I'm air testing through the center support bolt and the ports in the case to the left and right of the bolt. I'm testing using 30 psi. I can hear the drums apply but I hear a decent amount of air leaking inside as well. My mods are: duel feed mod by way of removing the inner lip seal on the direct and forwardas well as 2nd sealing ring left off center support. I used scarf cut sealing rings in the center support and pump they were installed using blue trans gel. The drums are stock 1969 with no drilling for pressure relief but do have the stock checkball aluminum pistons. Is the air leaking normal or should I break it down and recheck lip seals? I was very careful not to damage them on install, all my clearances are spot on as well as backlash front and rear.

[Half-Inch Stud]

1 Port on one side of the bolt ought be plugged, afterall the choice to plug the Separator Plate bleed hole is easy and work, but the corresponding Case hole may bleed (a little) at the C-Support-Case surface.

A 1/4" cup plug (or sometimes a 1/4" shaft) can be driven in to the case hole for peace of mind.

Aside from thaaat, there will be concerning air leak noises when testing like that. A major noise could be due to the Center-Support Bushing health or lack thereof. The Babbit Center-Support bushing determines the life of the TH400 Direct Pack, i think, maybe even Reverse apply.

So, I ask; did you check the sungear shaft for slip-fit to the CenterSupport bushing?

[n20ta2]

Yes all good there. Replaced all bushings and seals everything looked good in the unit except the direct drum, it had some wear due ro the cast sealing rings on the center support so I replaced that drum with a perfect used th400 round style drum. I didn't install a cup plug into the case as I'm using a Coan rmv without a brake. I had a conversation with the tech line and they told me the valvebody will take care of the duel feed mod on that end. I'm guessing it's leaking past the sealing rings as I went heavy with the trans gel so I wouldn't chip them up.

[Half-Inch Stud]

Re-assuring if you can hear the Direct Piston apply.

[n20ta2]

Now I'm not so sure I do, definitely hear the intermediate, I think its just air on the two side holes.wonder if it's the trans gel plastered down sealing rings? Maybe I should clean those off and try again

[Half-Inch Stud]

Might be worth your time to pull the front pump, check FWD and DIR packs out of the case. Not easy getting the air psi into them huh.

[n20ta2]

Yeah good idea I think I will just to be safe. Your right it's not easy to get air to the drums once you start messing around with different seals and modifications.

[n20ta2]

It was the sealing rings, cleaned the trans gel off them and now dums apply

[chuckies76ta]

Originally Posted by n20ta2

My mods are: duel feed mod by way of removing the inner lip seal on the direct and forwardas well as 2nd sealing ring left off center support.pistons.

In the Forward drum you don't remove the center sealing ring. All 3 sealing rings get installed. Also they usually require a .060 hole drilled into the corner or the direct drum to prevent high rpm apply usually with a trans brake.

[n20ta2]

From all the research I've done you can, supposedly it does the same thing to the forward as the direct and allows more pressure to apply the piston. I'm only using 5 clutches in my forward and direct so I want all the apply pressure I can get.

[n20ta2]

I forgot ro.mention I didn't drill the direct drum bleed hole ,Coan said it wasn't necessary because I'm running a manual valvebody without a trans brake so the direct drum springs are stock as well as the front pump springs.

[chuckies76ta]

Originally Posted by n20ta2

From all the research I've done you can, supposedly it does the same thing to the forward as the direct and allows more pressure to apply the piston. I'm only using 5 clutches in my forward and direct so I want all the apply pressure I can get.

Ok, From what my understanding is the Forward drum is on all the time. The two chambers was just to slow down the apply so as not to have such a harsh shift into first. I'm not sure what your gaining by removing it. Anyhow, just a novice here so it's all a learning curve for me.
If you don't mind me asking, how much H/P and torque you throwing at this unit? Thanks

[n20ta2]

Originally Posted by chuckies76ta

Ok, From what my understanding is the Forward drum is on all the time. The two chambers was just to slow down the apply so as not to have such a harsh shift into first. I'm not sure what your gaining by removing it. Anyhow, just a novice here so it's all a learning curve for me.
If you don't mind me asking, how much H/P and torque you throwing at this unit? Thanks

Honestly im a novicw here too, I worked at a transmission shop as a kid but mostly just removed and replaced. I built a few units under supervision but that was 26 years ago! I built a 4l60e that worked great in my old 2004 gto but I used a transmission bench video off you tube that made that easy. So I'm actually following advice on the inner lip seal removal on the forward from Shawn on the mountains garage videos he posts up on YouTube. He seems like he knows his stuff and he leaves them out of both drums. I don't think I will feel much on the engagement with the 4000 stall convertor I'm using. This transmission is going behind my highport 461, I'm guessing somewhere around 650-700 hp max and I really couldn't guess on the torque but maybe 600? I opted for 5 thicker kolene steels and red clutches on both drums as I don't have a lathe for the pistons and I don't like the idea of running thinner power packs because of heat.

[chuckies76ta]

Oh Ok, Thanks for the info. I've watch lots of Shawn's videos too. I really enjoy listening to him...It's good to see you tackle your tranny.

[n20ta2]

Originally Posted by chuckies76ta

Oh Ok, Thanks for the info. I've watch lots of Shawn's videos too. I really enjoy listening to him...It's good to see you tackle your tranny.

Thanks! Yeah lol hope it works. I was very carefull with all my clearances and endplays. The only other Modifications I made were restricting the pump feed a bit and roller output instead of the selective washer. I used a case saver and spirolock underneath as well as on the sprag.

[chuckies76ta]

Originally Posted by n20ta2

Thanks! Yeah lol hope it works. I was very carefull with all my clearances and endplays. The only other Modifications I made were restricting the pump feed a bit and roller output instead of the selective washer. I used a case saver and spirolock underneath as well as on the sprag.

Cool. Ya it one of the best projects I have done so far. Lots of tricks in these builds. You can also use the 4L80E Direct drum in a TH400. They have a thicker intermediate outer race that engage the intermediate clutches. It also holds more Steels/Clutches depending on the piston you use. Case saver is a great upgrade as well as the heavy duty snap ring on intermediate pack. I think they use a 727 tranny snap ring. I replaced my Forward drum with an after market unit with input shaft. I also replaced the forward clutch hub which is also rollerized.

What valve body did you go with?

[n20ta2]

I went with a coan.