Info: TH400 suggestions

[frankenstien]

So i picked up a junker for parts for my 1974 gm truck, 3/4 ton. my truck currently has a 383/th350/np205 the junker has a 454/th400/205.

looking to turn the 454 into a 500-600hp 496 hopefully around 600 ft-lbs.

the truck weighs about 6200 lbs, 4.56 gears, 35'' tires. also about to put an all steel flatbed on it, and plan on beating on it

I have been reading up on kits for the last week or so, searched around on here a bit, but most on here are more for a duramax

so far I know you need to upgrade from the 8/16 element sprag to a 34 element sprag

I was also thinking of adding an 300M input shaft, I have one in the Th350 now, because i twisted off the stock one at one point.

heres a couple kits im looking at

https://transmissioncenter.net/shop...evel-2-th400-terminator-transmissions-k400l2/

^^^^has 34 element sprag

https://transmissioncenter.net/shop...our-level-3-th400-raptor-transmission-k400l3/

^^^ that one is probably overkill, comes with a billet input shaft and a billet forward clutch hub, 34 element sprag, red altos

https://transmissioncenter.net/shop...our-level-3-th400-raptor-transmission-k400l3/

^^^ that one has red altos and the 34 element sprag

dont know much about either company, both seem to have good reviews.

Anyone have any suggestions of what i should put in this thing? or other places to check for a a rebuild kit

 

[A. Stock Lbz]

The first kit you posted will be just fine for what you are doing. I run a th400 in my turbo race/street car, makes 1050hp at the wheels. I still have the stock shafts in it with a build similar to the first kit you posted. 4l80 second gear clutch pack, 4l80 band, 34 element sprag, and the line pressure bumped up. Been beating on it for 2 years and fluid and filters always look new. Never heard of that company I just had a local trans builder do mine.

 

[onebaddmaxxx]

The first kit you posted will be just fine for what you are doing. I run a th400 in my turbo race/street car, makes 1050hp at the wheels. I still have the stock shafts in it with a build similar to the first kit you posted. 4l80 second gear clutch pack, 4l80 band, 34 element sprag, and the line pressure bumped up. Been beating on it for 2 years and fluid and filters always look new. Never heard of that company I just had a local trans builder do mine.

At that power it’s hard to believe the directs haven’t burned up with a stock drum. Most of the time a builder will swap a billet drum in after 800hp.

I agree don’t need billet shafts at that power.

 

[hondarider552]

I have a billet drum, input, output and 34 sprag. It's a stage 3 from Rossler transmissions. I also had the converter made as a 4L80 front cover and use a 4l80 flexplate due to 6 converter bolts instead of the th400 normal 3 bolts.

 

[A. Stock Lbz]

At that power it’s hard to believe the directs haven’t burned up with a stock drum. Most of the time a builder will swap a billet drum in after 800hp.

I agree don’t need billet shafts at that power.

That will be the next upgrade when it comes out again. It lives in the 800whp range most of the time.

 

[frankenstien]

The first kit you posted will be just fine for what you are doing. I run a th400 in my turbo race/street car, makes 1050hp at the wheels. I still have the stock shafts in it with a build similar to the first kit you posted. 4l80 second gear clutch pack, 4l80 band, 34 element sprag, and the line pressure bumped up. Been beating on it for 2 years and fluid and filters always look new. Never heard of that company I just had a local trans builder do mine.

How much does your car weigh? Do you know if the converter feed is down sized on yours? I have a book on the 400's I've been reading through, says you can drill, tap, plug and re drill the converter fill hole smaller to help with blooming apparently it can be an issue?

As far as input shaft go, only looking as I twisted off the end of the th350 once, replaced it with a "torsional" input shaft from ATI performance.

 

[A. Stock Lbz]

How much does your car weigh? Do you know if the converter feed is down sized on yours? I have a book on the 400's I've been reading through, says you can drill, tap, plug and re drill the converter fill hole smaller to help with blooming apparently it can be an issue?

As far as input shaft go, only looking as I twisted off the end of the th350 once, replaced it with a "torsional" input shaft from ATI performance.

Car weighs 3450 with me in it. Yes you can drill and tap the converter feed if you are having problems with thrust bearing going out. Mine is stock size, haven't had a problem with it yet

 

[frankenstien]

Car weighs 3450 with me in it. Yes you can drill and tap the converter feed if you are having problems with thrust bearing going out. Mine is stock size, haven't had a problem with it yet

yeah, i want to do it right the first time without having to pull the trans out again, could always use a converter with an anti baloon plate

 

[A. Stock Lbz]

yeah, i want to do it right the first time without having to pull the trans out again, could always use a converter with an anti baloon plate

I run a ptc 9.5 in with anti ballooning plates. They have a nice budget 10" converter with anti balloonin plates for $450

 

[frankenstien]

well i called the PATC place today and talked to them a little bit about the lower end kit, it has the brown or blue clutches for everything except the intermediate's are a red alto, the guy seemed confident that it would hold my 550-600hp, they rate their kits at 800hp, how accurate are they? no idea. probably going to buy an input shaft just to be on the safe side.

ill take a look at ptc converters, i dont know what the motor will need for a stall if anything special at all yet