TH400 rebuild kit?
TH400 rebuild kit? So I just bought a cheap '78 TH400 with ~50k miles on it and I want to rebuild it before putting it in my car (~650hp 3,000lb Ls fox).
I know practically nothing about automatics so I am looking to do this just as much to gain experience as to save some money.
I have some how-to books on the way as well as plan to re-watch a bunch of youtube videos...however I am not sure what "kit" to buy, specifically what clutches do I want? Some say Alto is good, others say it's junk, go BW. Some say Kolene steels are a waste, others love them. Some say unless the bushings are really bad, don't change them as most aftermarket bushings are oversize even compared to a mildly worn factory bushing. the list goes on.
The only mods I am certain of are putting a restrictor in the pump to lesson thrust load on the engine and I wil be running a RMVB, but no transbrake.
I found a few threads on here but the links are now bad.
Thanks for any input,
-Jarrod
I know practically nothing about automatics so I am looking to do this just as much to gain experience as to save some money.
I have some how-to books on the way as well as plan to re-watch a bunch of youtube videos...however I am not sure what "kit" to buy, specifically what clutches do I want? Some say Alto is good, others say it's junk, go BW. Some say Kolene steels are a waste, others love them. Some say unless the bushings are really bad, don't change them as most aftermarket bushings are oversize even compared to a mildly worn factory bushing. the list goes on.
The only mods I am certain of are putting a restrictor in the pump to lesson thrust load on the engine and I wil be running a RMVB, but no transbrake.
I found a few threads on here but the links are now bad.
Thanks for any input,
-Jarrod
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Joined: Jan 2015
Posts: 1,114
Likes: 33
From: Fort Worth, Texas
I wouldn't use Alto Red's in anything, Sure....They will work OK in a TH400 but I believe High Energy frictions are far superior. Kolene steels are a waste of money!
I don't have issues with replacing bushings on ANY transmission, The trick is NOT to beat them in with a hammer, Use a small hydraulic press or more preferably a Arbor Press to install them.
I prefer Clevite, Federal Mogul, & Dura-Bond replacements & Sonnax for specialty bushings.......However, Even the cheap Chinese "SAP" bushings don't normally give problems.
Sounds like someone is blaming products instead of their Ham Fisted practices!
If funds allow it......A Aluminum Direct Drum w/ a 36 Element Sprag is excellent upgrade! If not......Get a late 4L80E Drum with a 34 Element Sprag.
A HD Intermediate Clutch Snap Ring is a MUST with fixed line pressure.
A '78 TH400 may have the "Multi-Piece" stamped steel pistons in the Forward/Intermediate/Direct clutches......Don't run these! They can come apart & burn a clutch up, Run the Aluminum versions in the Intermediate & Direct Clutch......And the Forward too if they don't cost to much, You can run a 4L80E Direct "Bonded" Steel Piston in the Forward Drum IF you use 4L80E return spring assembly.
High Rate piston return springs in the Direct Drum & Drill a .055" bleed hole at the edge of the drum.
Rollerize the Output!, Repurpose the 4 tang thrust washer between the 2 Carriers & toss the plastic thrust washer.
A Forged/Billet Rollerized Forward Hub is a good upgrade, To save money your can run a Steel 4L80E Forward Hub & machine it for a bearing. I would not run a Cast TH400 Hub on a car capable of 9's in the 1/4.
Set all FOUR end-play locations!.....Let me know if you need help with this.
No "kit" will come with everything you need....The absolute best case scenario is getting everything on one order.
Tear the unit down & go from there!
I don't have issues with replacing bushings on ANY transmission, The trick is NOT to beat them in with a hammer, Use a small hydraulic press or more preferably a Arbor Press to install them.
I prefer Clevite, Federal Mogul, & Dura-Bond replacements & Sonnax for specialty bushings.......However, Even the cheap Chinese "SAP" bushings don't normally give problems.
Sounds like someone is blaming products instead of their Ham Fisted practices!
If funds allow it......A Aluminum Direct Drum w/ a 36 Element Sprag is excellent upgrade! If not......Get a late 4L80E Drum with a 34 Element Sprag.
A HD Intermediate Clutch Snap Ring is a MUST with fixed line pressure.
A '78 TH400 may have the "Multi-Piece" stamped steel pistons in the Forward/Intermediate/Direct clutches......Don't run these! They can come apart & burn a clutch up, Run the Aluminum versions in the Intermediate & Direct Clutch......And the Forward too if they don't cost to much, You can run a 4L80E Direct "Bonded" Steel Piston in the Forward Drum IF you use 4L80E return spring assembly.
High Rate piston return springs in the Direct Drum & Drill a .055" bleed hole at the edge of the drum.
Rollerize the Output!, Repurpose the 4 tang thrust washer between the 2 Carriers & toss the plastic thrust washer.
A Forged/Billet Rollerized Forward Hub is a good upgrade, To save money your can run a Steel 4L80E Forward Hub & machine it for a bearing. I would not run a Cast TH400 Hub on a car capable of 9's in the 1/4.
Set all FOUR end-play locations!.....Let me know if you need help with this.
No "kit" will come with everything you need....The absolute best case scenario is getting everything on one order.
Tear the unit down & go from there!
