Technical auto transmission for 55 gasser

Have a friend that has built a 55 Chevrolet gasser with a 4 speed transmission. Between fighting clutches and a bad left knee he has decided to go with an automatic. His small block probably makes a legitimate 425 hp and is shifted at 7000. He contacted a company in Texas that sells racing transmissions and they tell him that he needs a powerglide and that a 350 won't shift at 7000. Any suggestions as to what transmission to run. Needs something that is dependable and affordable. I have my opinions but there are many here who know more than I about auto transmissions.
Mark? Butch? Your suggestions? Anybody?
Pete

 

I know of plenty th350's being shifted at 7,000 and higher, I'm not sure it has the power to weight to run a glide.

 

Sounds like to me the racing transmission guy only sells PG. As far as I know all the NHRA stockers that run TH-350s shift them over 7000rpm. I got a glide in my race car but it only weighs 2000lbs. in my 57 I am thinking of running a 350 or 400 TH because it's heavier around 3450lbs and I could use that extra gear. He should talk to other "racing transmission" guys.

Pat

 

With a auto transmission the engine my want to shift at a different rpm.

 

Contact another trans co.
Will this thing see street miles ?

 

No street miles. I'm in agreement with all of the above but wanted him to hear it from more than just me.
All comments appreciated.
Pete

 

POWERGLIDE, hands down; there's a reason everyone uses them, they just flat out work in drag racing. It won't be anywhere as near as much fun as a 4-speed manual however, or maybe even a 3 speed automatic, and the 2 gears of a Powerglide can be a little boring, especially on a street car. A stock case Glide and planetary assembly will live at that HP level, and be lighter than a TH-350. But, if your friend has a bunch of money, then a complete aftermarket "Powerglide", not that he really needs that. And anyone can build a Glide with a little guidance. A TH350 needs to much to make one live for long, especially in the sprag assembly, but even those have gotten better with "mechanical diodes" or TH-400 style sprag assemblies; TH-350's also tend to have weak bellhousings. Whatever direction (Glide or TH-350), get a converter built for his application (engine size, cam specs, car weight, rear end gearing, tire size, etc). POWERGLIDE. I am Butch/56sedandelivery.

 

What about a 400? I know they eat some power but it ought to be cheap and last forever.
Pete

 

stock TH400....

But that's just a suggestion.

How much money does he have?
Does the car need to go as quick as it possibly can?
Is it a sort of period correct car? or does it have lots of modern stuff on the engine, etc

 

I've got lots of questions here, too.
No street miles? Manual valve body okay? T brake? Air shifter?
So, is it for a particular association? Bracket racing?
Fast as possible, given the engine limitations?
Just HAMB drags and such? Grudge racing with his buddies?
Need to know this stuff before making a recommendation .

 

No street miles.
Manual valve body ok.
No trans brake.
No air shifter.
Hamb drags, local nostalgia events, limited bracket racing.
Just a fun car.
Doesn't want to spend a pile of money but likes to do things right.
It is pretty much a period correct car. Stock front suspension, 9" rear, 5.13, ladder bars, 9 inch slicks.
Pete

 

TH350 came along in 69. The PG wasn't used for racing until when, the late 70s? TH400 is a lot less expensive these days than an iron Hydramatic.

 

Aluminum Powerglides were used from about 1971 and newer in Stock , Super / Stock. Some of those cars required a 2 speed . (67-68 350 / 295's ) . 69's could go either way, but a lot of the guys still used the 'glide, claiming it was more consistent and easier to hook up.. As the tires got bigger and better, the 3 speeds came back. Now it's all T 200's.
Anyway, I still am not sure if we need to stay somewhat retro with this package.
If not, I'd do a T350 for the fun factor. A 400 would leave too much e.t. on the table, and a glide would feel about a half second slower, even if it's not.

 

Surprised nobody is arguing with me here. Must be losing my touch.
Okay then, he should use a T 200, Turbo Action forward manual valve body and shifter. Sonnax billet servo, wide, welded Kevlar band. 2.74 low will make it even more fun.
425 isn't much ,for a 355. It should live a long time .
8 '' converter, matched to peak torque and cam duration..Which is what, @.050?
Carburetor?

 

First gear ratio on a PG sucks, unless you have some serious power.

 

Quote "Hamb drags, local nostalgia events, It is pretty much a period correct car."

To me this means it should have an early B&M shifted Hydromatic, but if we're trying to go fast on a budget then by all means a TH350 is more than enough.

 

This one has a 400 Turbo, runs 10.80's very heavy 3700 lbs.

 

I agree ..but nobody used Hydro Sticks in Tri 5 unblown SB gasser combos. They used 4 speeds.
Seeing the stick deal is now out of the picture, what difference does it make?

 

Marty, 425 hp ain't gonna get him there, so it's all academic.

 

Turbo 400 and B&M series 60 shifter.

 

67 shifter...only two years away from using a th350

 

I'd say it comes down to if those tenths that you get are worth the price over a good solid turbo 400. Actually the tenths are only all that valuable in heads up classes anyhow. If you are running brackets it's reliability and consistency that count.

 

Let's see...Last 400 I had was in a Class A motorhome.. Before that, I had a 70 CDV 472 @ 5000 #.
Still think a 400 is way overkill in a 3500# SBC car.
Besides, our friend's trans builder can't build a TH 350 that works right. Anyone think he can build a 400?

 

I still say, if you're SERIOUS (or your friend is serious), a Powerglide. But, if there's nothing really special about the car, or if it see's some street time (Powerglides are really boring on the street) then go with a TH-400; they're heavier, and they take a little more horsepower out of the equation, but they're really hard to actually break (as opposed to normal wear and tear). You can build a TH-350 that'll do the job, but it'll need some fairly costly aftermarket parts, especially to beef up the sprag assembly. A Powerglide for your car = a converter, a "shift kit" (just re-drill the separator plate and use a different pressure regulator spring), and a steel direct hub (you'd be surprised how many guys don't even use one of those and get by using the stock cast iron piece); done; you can also up the direct clutch pack with thin plates and steels WITHOUT having to do any machining, and ANYONE can build a Glide. Mechanics or transmission builders = $$$$$. The TH-200 metrics are seeing a LOT of use in Stock and Super Stock/GT classes , but they are EXPENSIVE!!! Something that has't even been discussed yet is the extra cost of converting the car to an automatic. Tri-Five cars with manual transmissions had the trans itself just "hanging" off the bell-housing (stock setup). Most guys will then convert the engine to side mount (from front mounts), and add a transmission cross-member/mount with an automatic changeover(lots of pros/cons on how to mount the engine/trans). Then you'll need a trans shield/blanket, a transmission cooler, a shifter, a neutral safety switch, and possible having to swap slip yokes and/or shorten the drive-shaft; are the trans side mounts going to be deleted?. I know guys that do use a TH-350 with big blocks, and do it with nothing more than a stock rebuild with a hardened sprag race, and make them work/last, and then there are guys that blow them apart with a mild 350 engine. My Sedan Delivery, after it gets the pseudo-Junior Stocker makeover, with a 57 block based 265, will get one of MY built aluminum Powerglides. The OT Bracket Car with a BBC has a TH-400. One car's way underpowered, and one's a really heavy land yacht (it really needs the extra, 3rd gear). Check in over at YellowBullet.Com, in the transmission forum, if you want to get even more confused about what to do. I am Butch/56sedandelivery.

 

Thanks for all of the help. Visited with Ron yesterday for a couple of hours and he has decided to go with a th350 built by someone around Dewey, Oklahoma. Seems he has built several for bracket cars running at Tulsa.
Ron is just out to have a little fun. In the '60's he ran a 1956 Chevrolet in E/G car that was very competitive locally with a 4 speed. Wanted to duplicate that but old bodies don't always cooperate.
Pete

 

i have a glide in my austin healy with a 462 inch bb chevy but it only weights 2400 lbs....

 

Good points, Butch, about the installation.
Another point, not yet raised, is the camshaft.
A stick car ,shifted at 7 grand, most likely won't like being shifted that high with a 3 speed automatic.Especially a relatively mild 425 hp combo. So the whole combo will need to be changed, or prepare for a big loss in e.t.
Also , no reason why a TH 350 would take a bunch of expensive parts at this power level. What are we talking about..maybe a 12 second car?
A hardened sprag race is about all one needs. One thing you don't want to do is jack up the line pressure and stick in a wham bam shift kit. That will only slow it down and wear out parts.
If he's determined to shift it at 7000, all that's needed is to toss out the governor, plug and loop the passages in the case, block down the low gear blow off valve, and then manually shift it wherever he wants.
Still not mentioned is it's going to take a light weight 8" converter at 4400 + stall, to run anywhere near what the 4 speed ran. More expense there.
Also, don't let anyone tell you he doesn't need a trans cooler for strip only.

 

Every one is talking about the money involved in building a trans. My friend had an ot car, serious street car maybe 500 hp. He took a glide and a turbo 400 to his transmission guy. The guy said that he should run the glide. For the cost of $4000 he could build him a pretty good trans one that should be reliable. For $5600 he could build him one that his car would never break. Both prices are plus the converter. I thought that was way high in both cases.
What should be the cost of building a "bulletproof" trans be? 500hp 3200pound car on street slicks.

 

Probably going to dance around a bit on this one.
There are a lot of factors involved in the pricing of race transmissions.
First, you didn't mention whether core was included.I'd assume so.
Personally, I won't build any anymore, unless the person has a core. Short Chevy 350 stuff is getting a bit harder to come by. It takes time (and money) to chase around after one.
Also, the builder's reputation has to be covered for the type of abuse the trans will get. Heavy car, T-brake, nitrous, etc.
Another thing is whether or not he wants to recommend an aftermarket case. He has to venture a guess as to how solid and stable the customer's chassis will be.
I would say you have to shop around and compare whether all items used are name brand. Then check the builder's reputation. Has he been around a while? Does he build anything that wins races?
Sorry for the non answer.

 

If he wants a auto to act like a 4 gear at the track it would not be a 500 dollar rebuild for any auto.