Projects Advice on a mild custom 1950 Chevy

Hello folks, I have a 1950 Chevy Sport Coupe with a 235 cid Power -glide. What I need to know if anyone has upgraded the gears in their original differentials to lower the RPM's on the highway. I want to be able to cruise at 60 65 mph without topping the tachometer out at 3,500. Any advice would be helpful.
Thanks in advance,
Bob

 

Saw pics of your car on your introduction post. Nice ride!

I'm no expert, pretty new to the classic/custom car stuff.....but from what I've read and searched, the best way to accomplish what you want to do is to either change out the rear end gears to a 3.55:1 if that hasn't already been done, or convert to an open driveline.

A quick search online told me this...."This 235-cubic-inch (3.9 L) version was added to cars in 1950 to complement the new Powerglide automatic transmission, and 3.55:1 rear differential. The 216-cubic-inch (3.5 L) continued to be standard powerplant for cars with the three-speed manual transmission until 1953, when the 235-cubic-inch (3.9 L) became the standard powerplant on all Chevrolet passenger cars.

If you already have a "powerglide" rear end, (the 3.55:1 ratio) I don't know that there are many options left.


Check out Patrick's Antique Cars online. He has parts listed for the rear end upgrade. There are a few others too I believe.

I am working on building a 235 for my sedan delivery project, but will be going with a T5 transmission and an S10 rear end.....looking to run 2300 rpm around 70 mph.

 

I just got my hands on front and rear end out of a 54 powerglide car and I'm about to swap into my 50. Same reason as you. Hope to get better cruising speed, better brakes and the front swap should lower the front a bit as well.

 

Bob, If your coupe came with a P'Glide you should already have the 3.55's. The next possible method to improve your highway cruising is to find and install a TRUCKSTELL overdrive. Truckstell's were a dealer installed option for 1946 through 1954 Chevrolets. 1949-1954's used a Model 103 while earlier cars used a Model 101. The difference was in the input shaft length to better clear the drive shaft tunnel in the lower profiled later models.
These units clamp onto a shortened torque tube and impeller shaft so the is no need to do a rear end swap. They provide a 28% overdrive so they make a tremendous difference in RPM/ Roadspeed.
So go digging in all the old wrecking yards, and usual sources ETC. Be sure to get as much of all the purely mechanical linkage that comes under the dash and firewall, you'll need it to engage/disengage the unit. Although they probably never installed them on automatic cars, I have one behind a 4spd Hydromatic and it works just fine, I can even split shift it.
There are several of us on HAMB that have and use them, They are very good units and real conversation pieces. I have a 103 in my 54 GMC PU and can knock off 41 second miles after miles @ under 2800 RPM. You can do the math on that MPH. That should be good enough for you. If you're interested, check out my profile albums for pics of my rig.
Best Regards and good luck with all your endeavors, KB.

 

To further "peek" your interest in the Truckstell OD, let me make some critical points. The Truckstell was designed to work with your car. Next consideration is always $. If you find a Truckstell it will probably cost you about $1200-$1500 installed. If you go a different way, you'll need to first change out the rearend and buy a driveshaft, have it sized and balanced for your installation. If you want to stay with an automatic overdrive transmission you will need an adapter of some kind and a new trans mount. Bendsendt are a $1000 roughly.
If you decide to go with a T5 or even an old chevy 3spdOD stick trans you'll need to setup a clutch pedal and bracketry as well as shift linkage and a stick bellhousing. There alone is a significant amount work and money doing all of that.
So whether you consider cost or complexity, a Truckstell will be the best way to go, IF YOU CAN FIND ONE! Six have passed through my shop so I know they are out there.
Best regards and good luck with all your endeavors, KB.

 

3500 RPM is cranking for a spray oiled Chevy. Power-Glide rears were 3:55 's.
It's hard to fathom those RPM's at 65 MPH with 3:55 gears.
I'm thinking maybe 4:11's in the car now?
Math guys, help me out!

 

Thank you everyone for your advice, I will look into all of these possibilities. Hopefully, by next spring I will have accomplished setting up a car that will do much better on the highway. However, to nice out to tie it up, just have to stick to rural roads (which my wife thinks are better anyway). This is truly one of the best web sites I have ever been on for info. I am so tired of the others with everyone tearing each others rides apart.
Thanks again guys,
Bob