The Stovebolt Site Forums The Shop Area Driveline Rear Axle upgrade or swap on 1950 1/2 ton

Hello to all. Im brand new here but this looks like a great site. I just purchased a 1950 1/2 ton (I believe a 3100?) I want to leave the 6cly and 4 speed in it, I already have the info of how to get to 5 bolt hubs on the front. Now I need to do something with the rear end. I need to decrease the gear ratio and convert to 5 bolt hubs. This truck has a sealed drive shaft. Id be fine to leave the axel in the truck if there is an easy way to accomplish these two things and therefore leaving it even more original. If not....how does one swap the rear-end when the tranny has the enclosed driveshaft? Any advice will be GREATLY appreciated.

Maybe torque tube cars have 5 lug axles, other than that you are looking at a different diff. A few places offer 3.55 gearing but it's pretty pricey.


Why do you want 5 bolt wheels on it?

Welcome to The Stovebolt. You can get a 3:55 ring and pinion gear set for your truck from Patrick's. I think mine was about $150 when I got it from him. That will reduce your RPM's with your SM420 tranny to a comfortable level allowing 65MPH cruising easily if you have the stock size tires/wheels. You may have to wait a while if he's out of stock. I can't help you with the 5 lug question but I'm sure someone else will chime in. Good luck.

Thanks guys! Actually, I just found 6 bolt wheels like I want, so no need to change to the 5 bolt. I'll definitely go to Patricks for the 3:55 ring. That will solve a lot very easily. Im not familiar with Patricks. What is the rest of the name?

Whats wrong with the 6 lug parts?

Walt Williams
La Verkin, UT

There are many ways to solve this problem. I too have a 1950 3100. I went to a 1962 261 engine so I had full pressure and full flow oil filtering, then put a Borg R10 Overdrive transmission behind it. Its a direct bolt up. I then went to a 1955 1st series rear end because that is also a direct bolt up with a 3.90 gear set. I then got new 1954 spec'd leaf springs all the way around and had a 1964 Suburban driveshaft shortened. Since I like the 4 on the floor shifter, I made a shifter that comes up through the floor in the 4 speed location, and that's how I get highway speeds and more reliability out of mine. The entire restoration is documented here:

devestechnet.com

Do you still want to keep your 6 cylinder engine?
Do you still want to keep your 4-speed and torque-tube?
It looks like to original 6 bolt wheels are OK?

If so, the 3.55 ring & pinion gears will work for you.

Be careful with Patrick's. He can be VERY slow is fulfilling orders. Be sure he guarantees that he has it in stock.

mothertrucker might still sell the R&P set (at a good price): [email protected]

http://www.classicparts.com/1941-54-Rear-End-Gears/productinfo/93-511/#.VbGnKbe1WRA
make sure they have it in stock

Installation parts kit:
http://www.classicparts.com/1951-54-Rear-End-Gear-Installation-Kit/productinfo/93-512B/#.VbGnfLe1WRA

Thank you all for the information and advice. Great site and great help!

I hear he still has the best price around on the gears.

http://www.jalopyjournal.com/forum/...-ring-pinion-gears.923013/#post-11086879



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I heard that this gear set won't fit a canadian made gmc rear end, is that true?

Hi, Dmax, On my Canadain 49 chev pu. the ring gear will fit the carrier, BUT the bolt holes will NOT line up, so I had a machine shop slot the 3:55 ring gear to match the carrier. I took in the old 4:11 ring gear and the new 3:55 ring gear so they could machine it right, they did a good job. Also order the bearing kit and the front bushing for the drive shaft tube and a speedo conversion unit so the speedo will show the right speed. Only in Canada EH, Have fun, Brian PS, Check with Curt B, he is in Alberta and on Stovebolt.

I use Patrick's 3.55 gears in my green terd and love it. Keep in mind wanting highway speed gears forces you to want highway speed brakes.