VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc 235 and an automatic transmission

I have a 57 chevy p/u that is all stock with a good running original 235. But highway driving is not ideal. I have learned the previous owner put a period correct Chevy car rear axle to help with speed, but I'm looking at a new transmission. I have a line on a good working 3 speed automatic Turbo 400 that came out of a 53 Chevy pickup. Will this be a good option? Will it mate directly to my 235 (it was used with a 235 so the owner says it will)? And will it improve my highway speed?
Eventually in a few years I may swap in a modern engine/transmission, but for now I'm looking for something to just make it a little more drive-able.
Thanks,

A three speed T.H. 400 will NOT change the engine speed on the highway, A T.H. 700 is a 4 speed will as 4th gear is an over drive.

THANK YOU! You just saved me some money and time. TH 700 - will that mate with a 235? My uncle gave me a 700R4, but I've been told the expense of getting that to work with a 235 (adapter and such) would make it almost as expensive as just putting a 350 Chevy in it and updating the whole thing. I'm not a stickler on keeping it stock. I just want it more driveable. But I also don't want to change a good working engine for no reason if I can simply swap in a different transmission.

PS. I am NOT a mechanic so I an naive on a lot of this. I have a mechanic that I trust and he'll be doing the work, but I need to know enough to bring it to him

First I would determine if it really is a "car" rear axle and then dtermine the ratio, If it is the common 1955-1964 unit the rear cover wll be welded in place. Truck covers were bolted on.

It's bolted, but when we went to replace the axle seals on it we found out it was car. The guy I bought it from confirmed he swapped that out to increase speed. Perhaps it was from an earlier era? Not sure.

It can not be for a pre 1954 car because those cars had an enclosed drive shaft and would not connect up to your drive shaft,
The 1957 1/2 ton rear seals also fit 1933-1936 passenger cars
There will be a casting number on the front casting of the differential, large raised numbers. This will tell a big part of the story.

Thanks, I'll crawl under it and look!

I am confused by your first post. You state that you have line on a Turbo 400 our of a ‘53 pickup. The TurboHydramatic 400 model as I know it is a 3 speed automatic that was used for the higher toque Chevy engines in the late 60’s and early 70’s. As a 3 speed the top gear was a direct drive (1:1 ratio).

Also the Turbo 400 did not even exist in 1953. As noted it is designed for an open driveshaft application.

Any transmission with a direct drive top gear will not change the engine speed to ground speed relation that you currently have. You will either need to adapt an overdrive transmission, install an overdrive unit, or change the rear axle ratio. The downside of changing the rear axle ratio is that it will reduce your acceleration.

My 57 1/2 ton with 270 GMC engine and stock transmission limits the comfortable top cruising speed to about 60mph. With my steering correctly set up and all worn parts replaced I find the solid front axle is the limit in the cruising speed. It still takes effort on my part to relaxingly cruise in my lane. Something may be wrong with my truck that i am unaware of but there is no way i could compete with the modern traffic flow. If my vehicle is loaded I drive much slower even with adequate engine power.

Thanks for the replies. I only shared what was told to me by the seller, so it sounds as though the transmission wasn't original to his 53. Either way if it isn't going to do what I want, I'll pass. My mechanic suggested that ultimately, for what I want to achieve, a more modern engine (perhaps a 350) with an overdrive transmission is what I want. My mechanical knowledge is very basic so all of the talk about what transmission works with what engine and what gear ratio is simply out of my wheelhouse. LOL
Live Wannchev said, I can cruise at 60 mph. But the sweet spot is really 50-55mph. Getting it on the highway is not pleasant as many cars give you a thumbs up, but some are just pissed you're going so slow!

Over the years there have been many posts about this same subject. The original intent is to find a way to drive these older classic vehicles faster to keep up with today's traffic.

It is relatively east to change the rear axle ratio or even the whole powertrain to achieve that.

The real issue is whether you want to drive that vehicle at higher speeds with its original design suspension, brakes, and steering.

In your case a minor change in rear axle ratio should let you drive comfortably and safely at 60 mph if the rest of the vehicle is in good condition.

Out of curiosity, should I eventually go with a 350/ auto combination: What would I "have" to change? Could I run that with drum brakes or would I have to update to front disc power brakes? I've updated to a dual chamber master cylinder is all and have had no issues, but that's driving around town at 50-55 mph. Would I need power steering or could I continue to drive as is at least for a while and modernize things a bit at a time as finances allowed?

My thoughts are exactly that - my thoughts. What an owner does with their vehicle is their choice. You would not "have" to change anything or only as much as you want.

My experience and knowledge is based on keeping these classic Chevy's more original. I have talked to many others who have started down the path you are considering. The success rate varies. That is why you see so many "project" vehicles for sale.

If your goal is a vehicle that will comfortably and safely cruise on today's highways while looking like a 50's vehicle you might want to talk to others who have done street rods or custom conversions. There are some on VCCA Chat.

What I have learned from the people who have done that work is very key. Have a complete end plan before you start. While you might be able to do some of the work a piece at a time, without a plan you will end up with incompatible solutions or having to redo portions.

With cars I have followed a basic rule. If you increase power, top speed etc. Then it is best to equally increase the braking and handling of the car. If you have to perform an emergency stop will you current brakes stop you at the increased speed you plan to go? If you have to suddenly swerve will your current suspension hold up to the added force at a higher speed. Looking at this from purely a safety aspect. I understand these older cars are not as safe but anything that increases safety is a plus.