TH400 build

[Tonimus]

My buddy and I have started the slow build for the TH400 going into his '63 Chevy II. The 4L80E in it was acting funny going down the drag strip, so we're going to yank it and rebuild it later. Right now it's a driver, so we're going to tackle the TH400 going in it first.

Started with a gross TH400 that came out of a '72 C20. Not the original trans for the truck, but was rebuild and later installed by someone else. Has a '73 tag on the side.

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Yanked the guts out.

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Found out that despite the 6 bolt pump, it's an 8 bolt case. That saves us $300 since it'll work with a SFI bellhousing.

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Cut the bellhousing off.

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Put it in our drum of old gas and diesel for soaking to clean.

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After a soak and a hosing off. A few more and it'll be good as new.

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We've already picked up some new thick center support snap rings, torrington bearing for the rear of the case, Sonnax roller forward clutch hub, Kent-Moore TH400 tool set, Ron Sessions' book, the ATSG manual, and have watched a LOT of YouTube.

Keep tuned in for further slow updates as we get parts and start reassembly.

If anyone has a 4L80e direct drum assembly they'd part with, we're in need of one.

 

[NickTransmissions]

Good luck with the rebuild - check out my TH400 information thread and Youtube playlist on these units and tag me in posts if you need any help.

TH400

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[Tonimus]

I have watched most of your TH400 videos. Definitely helped me out.

 

[Keith Seymore]

What's the motivation for using an SFI bell housing? How quick is the Chevy II?

K

 

[Matt69olds]

Good lord, don’t cut up a good Chevy case for a ultrabell!! Good Chevy cores are getting too hard to find.

Find a BOP 400, those are a dime a dozen. Added bonus, they are almost always 8 bolt pumps, and if you find a early core from a land yacht, more than likely have the heavy duty case with thicker pan rails and additional webbing around the extension housing. I buy all the BOP cores I can find with broken bellhousings for exactly this reason.

If you can’t find a 4L80 drum, Teal Automotive in Dunkirk, Indiana will have them. Last time I bought one I think I paid 75 bucks. No clue what shipping would cost.

 

[Tonimus]

What's the motivation for using an SFI bell housing? How quick is the Chevy II?

K

It ran a low 12 with a bad ignition coil and weird trans issues. It should run 10s the way it's set up. Shafiroff 427 SBC. I ran 11.5 in my Camaro that weighs 600 pounds more and makes 150 less horsepower.

Good lord, don’t cut up a good Chevy case for a ultrabell!! Good Chevy cores are getting too hard to find.

Find a BOP 400, those are a dime a dozen. Added bonus, they are almost always 8 bolt pumps, and if you find a early core from a land yacht, more than likely have the heavy duty case with thicker pan rails and additional webbing around the extension housing. I buy all the BOP cores I can find with broken bellhousings for exactly this reason.

If you can’t find a 4L80 drum, Teal Automotive in Dunkirk, Indiana will have them. Last time I bought one I think I paid 75 bucks. No clue what shipping would cost.

Not trying to be contrary or anything; this is the second time I've heard this. Other than "they're hard to find", what's the reason for not cutting them up? With a SFI bellhousing, it still fits anything that it would have originally.

I'm not saying that if I was buying a trans I wouldn't get a BOP since they ARE cheaper, but we already had the 8 bolt case.

 

[Beast496]

If anyone has a 4L80e direct drum assembly they'd part with, we're in need of one.

I'm pretty sure I have one sitting in a box that I was going to use on my build, then found a late 60's drum set up for six clutches, so I put the 4L80E drum on a shelf. I'll look today. I know I have a bunch of other odds and end parts and pieces, and some of them are of the "go fast" variety. If you get in a bind, just reach out.

 

[Matt69olds]

It ran a low 12 with a bad ignition coil and weird trans issues. It should run 10s the way it's set up. Shafiroff 427 SBC. I ran 11.5 in my Camaro that weighs 600 pounds more and makes 150 less horsepower.



Not trying to be contrary or anything; this is the second time I've heard this. Other than "they're hard to find", what's the reason for not cutting them up? With a SFI bellhousing, it still fits anything that it would have originally.

I'm not saying that if I was buying a trans I wouldn't get a BOP since they ARE cheaper, but we already had the 8 bolt case.

Chevy transmission’s fit Chevy engines. BOP transmissions fit 3 times as many different engine, and tend to be better castings. Obviously, if the bellhousing is cracked or missing pieces, it doesn’t matter. But given the choice, I’m cutting up the cheaper and better case.

 

[Tonimus]

Other than anecdotes, I've seen no actual evidence that BOP cases are actually any stronger than Chevy cases. At this point, I don't think anyone is going to take a bunch of cases and test them to destruction. Ultimately it doesn't matter about cutting off a bellhousing unless you're worried about originality.


Pics from the latest tank and clean.

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[Tonimus]

Primered with the '81 Camaro project in the back.

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[xm20k]

Chevy transmission’s fit Chevy engines. BOP transmissions fit 3 times as many different engine, and tend to be better castings. Obviously, if the bellhousing is cracked or missing pieces, it doesn’t matter. But given the choice, I’m cutting up the cheaper and better case.

Technically that trans will now fit even more applications as the bell can be swapped to bolt up to the back of a ton of non-GM engines.

Also, the bell is the failure point on the TH350/400 transmissions were as the powerglide it is the case that tends to pop first.

Any trans I've ever built to take 500 or more HP the bell is the first thing to get changed, a powerglide the whole case is tossed and swapped to an aftermarket, as far as 400 cases go the case can withstand up to around 1000-1200 with a bell and proper internals.

OP make sure you swap that forward clutch hub the stock casting is garbage. I replace these even on stock style rebuilds if it hasn't been done already.

Pardon Our Interruption

EDIT Also let me know if you need anything as far as hard parts go for it as I have the guts from 2 of them sitting here right now as well as a set of tail housings, pumps and an aftermarket billet reverse manual trans brake valve body, linkage parts etc.

 

[Tonimus]

Already got a roller Sonnax forward clutch hub, 4L80 intermediate clutch backing plate, thick snap ring from a 747, and now a 4L80 drum from Beast.

 

[NickTransmissions]

Already got a roller Sonnax forward clutch hub, 4L80 intermediate clutch backing plate, thick snap ring from a 747, and now a 4L80 drum from Beast.

I’d have a few different A518 fwd clutch snap rings on hand. Hardly ever been a build where I didn’t have to swap different thickness of that snap ring to dial in my int clutch. High rpm/racing units get more clearance than otherwise…

 

[Matt69olds]

Read this: great description and illustrations of the advantages of the heavy duty BOP case.

https://www.ckperformance.com/Tech-Blog/2018/11/TH400-Transmission-Case-Identification-and-Interchange

I have built hundreds of 400s making well over 1000hp using the stock case. Assuming the chassis and engine mounting is correct, the case is way down the list of upgrades.

Chris of CK performance died earlier this week. I talked with him many years ago when I was playing around with the 2004R trans. I learned a lot from him.

 

[Tonimus]

I’d have a few different A518 fwd clutch snap rings on hand. Hardly ever been a build where I didn’t have to swap different thickness of that snap ring to dial in my int clutch. High rpm/racing units get more clearance than otherwise…

The 727 and 518 snap rings are listed as the same. I got a kit to start that has 4 in it. .062", .074", .088", and .106".