Technical Thoughts on '57 Chevy Tranny Options?

Hey Everyone

I have always run a 4 speed ****** in my '57 "G***er" - Mild 454 BBC (460 ci), mostly street driven

Due to getting older (& lazier) I have pulled the 4 speed set-up & want to install an automatic. Being unfamiliar with either, and having good cores of each, should I go with a Turbo 400 with shift kit or a Turbo 350 with shift kit?

Thanks in advance

 

Turbo 400

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They are both good choices but with that many inches I would go for the 400. I am in the same situation as you only with a SBC 377". You might also want to consider a glide. But in mostly stock (shift kit) the 400 is probably the strongest but it uses the most amount of HP to turn although I never noticed this for my purposes (stock and super stock consider this factor). Where are you located? I got a couple of worked PG's here you could try.

Pat

 

Turbo 400 is what the General put behind the big blocks when the auto-trans box was checked. I had one in my youth, and abused it like any testosterone fueled young buck was expected too. Helluva transmission in my book. Made numerous 4-spd hot-shots tuck tail & grumble, all the way home...

 

400 for sure beefier. But if your driving on the street and got a low gear rear like 3:54. 3:73 or up why not a 700r4 beefy and od. Just a thought and option.

 

700R4 would need to be beefed up behind that engine. Which can be done, it's just somewhat more involved.

 

Based on your description of use - mild BBC mostly street driven - the 400 would be my choice.

 

i'll be odd man out - 2004r. http://extremeautomatics.com/th2004R.php << not necessarily recommending this place, although i've heard many good things, but they have a lot of info i needed deciding between this and a gear vendor for a non HAMB project.

 

Out of your 2 choices the 400, although I have a friend with a 427 (435hp spec) using a th350 in his 56. I kept my built th350 in my Henry J when I switched to big block, haven't driven it yet but it's already in the back of my mind as the weak point.

 

Thanks guys!

I was already leaning in the Turbo 400 direction, and you all reinforced my train of thought.

Turbo 400 for the win! - NOW, what is a good torque convertor for street/performance use?

(Remember, I'm a life-long Muncie user - this auto ****** stuff is new to me!)

 

Stick with the TH400, but convert it to a switch pitch ST400; uses a torque converter that can be "switched" between two different stall speeds; a street stall and a little higher race stall, if you will. "squirrel", here on the HAMB, can provide you with the details; finding the parts/transmission to use the parts from, may be the hard part. Olds/Cadillac/and possibly Pontiac used this transmission. They say to use the smaller torque converter from the ST-300. What I've wondered, is if the pump from the ST-300 can be used in a TH400 to do the conversion? Since the stator and input shaft splines are the same.....................................anyone know? I am Butch/56sdedandelivery.

 

X2


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Lot of things come into play with converter selection, engine specs, weight of car, rear gears and intended usage. Sometimes it's best to have that info when calling a reputable converter maker.

 

Given any consideration to the 4L80E? It's essentially a TH400 with OD, they share like 80% of the parts. They're plentiful as they were the transmissions used in GM 2wd trucks for years, and now the prices of the control units have come way down. The TCI EZTCU is like $700 and all you need is a TPS sensor, which is like $100. Is it more money than just running a regular old TH400? Yes. For sure. But depending on what rear end gear you're running, and considering you say you drive mostly on the street, you may really appreciate the OD for the civility and drivability of the car. Something to consider.

 

I remember pulling the T-10 out of my '32 and putting a 400 in it. Wouldn't do it today.

 

I remember laying on my back in my parents garage and pulling a turbo 375 onto my chest and bench pressing that SOB into place in my 56 Bel Air. Made my own bellhousing side mount brackets and used a 1st gen camaro crossmember. No wonder I hurt so much nowadays In case anybody's saying what the hell is a turbo 375? Its that funky 1965 or so turbo 400 with a turbo 350 size output shaft...

 

Actually, there are two TH 375 models...an A and a B. One is a beefed up TH 350 and the other a ‘detuned’ TH 400......

 

just couldn't make up their minds, huh?

 

I would use a Turbo 350. slightly lower gear ratios, lighter weight and less power to run. And they are strong enough to handle a big block, and towing duties.

 

4L80 overdrive turbo 400 gets my vote

 

I'm also a big fan of any transmission with an Overdrive.
They just give you the best of both worlds in that you can gear
the car for great acceleration & still have great cruising gear/low rpm

 

I always liked the TH400 myself, it all depends on what you want to do with it. I have a couple salted away for future projects, they at least make for a good core. How much cheaper is a TH350? Probably not much. I was looking for a performance automatic last year... had a wet dream project running through my brain pan.

This local shop builds a lot of good stuff for whatever you want to do.
http://www.fbperformance.com/GM-Transmissions/

 

Thanks Guys for the great options!

Since I have a good TH400 core I'm going to go that route. I'm leaning towards a "Freak Show Converters" convertor - any bad experience? Thanks!

 

Have your rebuilder install the 2.75 1st gear planetary set (vs usual 2.48 set)....stock GM piece used on various models

Ray

 

Showing my ignorance, but what is the benefit?

Thanks for your reply!

 

With the 2.75 first gear it will pull harder off the line. Second gear is 1.48, so it will some what get you closer to an equal ratio jump first to second and second to direct.

 

I did the 2.75 first gear set once, never really noticed much from it and it was expensive!!

Nothing like a Turbo 400 with a Hurst Autostick I shifter...

 

I also vote for the TH400 for service behind the big block. I converted from a 4 spd to a 400 with a Transgo shift kit in 1973, and am still using the same transmission. I am also running synthetic ATF, and that helps reduce heat and increase shifting speed.
Regarding the converter, I have gone back to a stock converter to match my more moderated driving habits. I like switch pitch torque converters, but you would want to talk to guys like Squirrel or one of the other people regarding the modifications required to make this change. To do this, you have to have the appropriate 400 case that was designed to accept the switch pitch modification, and you will need to pull the ****** apart to make the required internal changes.
Bob

 

Thanks for the great info!

 

Also make sure your th400 is not the bolt in yoke variety, that's a whole nother can of worms to avoid if you can. I made that mistake once and sure wish I knew about the problems, I would have had the output shaft changed to regular slip yoke variety in a heart beat.