Th400 deep pan and refresh?

[Scruffy49]

Truck made it 40 years without a transmission service that I know of. And after sitting/being lowered, now has no fluid showing on the stick.

I know, truck abuse, we inherited it when my 92 year old father in law died in 2018. Was mothballed to backup status with a permanent plate.

Plan to pull the engine and the transmission for freshening up. This is a factory installed Th400 behind a gutless wonder carbureted (factory) 4.3L V6. Our local transmission shops quite frankly suck.

Only want to do this once, so…
1. Which components kit for the “guts”?
2. What seals and pan gasket?
3. Will a standard duty finned cast aluminum pan be alright in a truck, or just buy the +2 or +3 quart to stick with a truck sized pan? This is a 6/8 static dropped, never tows but has a heavy period correct topper toy.

I’ve rebuilt 1 C6 and 1 727 previously. Added cast deep pans to those as well, they seemed to seal up better than the stamped, can’t be as grossly overtightened/warped. Thanks.

 

[Ricko1966]

I usually use 1qt deeper pan and a pickup extension. Then Rather than run an extra quart I run normal capacity,this keeps my fluid level lower for less chance of leaks,without starving my transmission for fluid.

 

[Beast496]

I usually use 1qt deeper pan and a pickup extension. Then Rather than run an extra quart I run normal capacity,this keeps my fluid level lower for less chance of leaks,without starving my transmission for fluid.

I actually do the same. I have my dipstick marked to .5in. below the sealing surface on an ATI deep finned pan. no more leaks for me lol.

to the OP's question for hard and soft parts, I go through Oregon Performance Transmission only because they're close, fast shipping, and I can build the kit based on only what i need.

TH400 Rebuild Kit TH-400 Master Overhaul Banner Box Set Automatic Transmission 3L80 GM

Check out the deal on TH400 Rebuild Kit TH-400 Master Overhaul Banner Box Set Automatic Transmission 3L80 GM at Oregon Performance Transmission

www.oregonperformancetransmission.com

 

[legopnuematic]

I used Cobra Transmission parts for the 904 in my Dart I rebuilt last year.

I was going to use Oregon based on recommendations here, at the time they had a few things out of stock that I needed, so I tried Cobra. Trans star is another option too if you have a local store.

No complaints. I do believe there there are not that many manufacturers of transmission parts, for example I think most kits use trans tec (trans star) paper and rubber kits, etc.

 

[NickTransmissions]

Truck made it 40 years without a transmission service that I know of. And after sitting/being lowered, now has no fluid showing on the stick.

I know, truck abuse, we inherited it when my 92 year old father in law died in 2018. Was mothballed to backup status with a permanent plate.

Plan to pull the engine and the transmission for freshening up. This is a factory installed Th400 behind a gutless wonder carbureted (factory) 4.3L V6. Our local transmission shops quite frankly suck.

Only want to do this once, so…
1. Which components kit for the “guts”?
2. What seals and pan gasket?
3. Will a standard duty finned cast aluminum pan be alright in a truck, or just buy the +2 or +3 quart to stick with a truck sized pan? This is a 6/8 static dropped, never tows but has a heavy period correct topper toy.

I’ve rebuilt 1 C6 and 1 727 previously. Added cast deep pans to those as well, they seemed to seal up better than the stamped, can’t be as grossly overtightened/warped. Thanks.

If you plan on rebuilding the unit, check out my TH400 thread if you haven't already - there's tons of info available covering all aspects of servicing and overhauling these transmissions:

TH400 Information Thread

Hi All, Since many of us own at least one GM Squarebody truck with a TH400, I figured I'd start another all-encompassing thread, this time on the Turbo Hydra Matic 400 aka THM400...I have basic facts, links and general information along with videos covering tear down and inspection, step by...

www.gmsquarebody.com

I have an entire play list on Youtube including two separate complete rebuilds - the TH475 rebuild series is what I'd recommend watching as it's the better, more informative of the two builds.

 

[Scruffy49]

If you plan on rebuilding the unit, check out my TH400 thread if you haven't already - there's tons of info available covering all aspects of servicing and overhauling these transmissions:

TH400 Information Thread

Hi All, Since many of us own at least one GM Squarebody truck with a TH400, I figured I'd start another all-encompassing thread, this time on the Turbo Hydra Matic 400 aka THM400...I have basic facts, links and general information along with videos covering tear down and inspection, step by...

www.gmsquarebody.com

I have an entire play list on Youtube including two separate complete rebuilds - the TH475 rebuild series is what I'd recommend watching as it's the better, more informative of the two builds.

I’ve read the thread. Will reread and look up the videos. Thank you