The Stovebolt Site Forums The Shop Area Driveline Swapping rear end

I have a 1958 GMC F 370 with a very low geared rear , 6.00 on the high side . What will increase this number? even swapping the complete axle is an option. What will fit and where do I locate one?

Hy Phillip Lott, first we have to establish exactly what rear axle your truck has. Is your truck equipped with a single speed or two speed rear axle? What are you trying to achieve by changing the rear axle ratio, more road speed, the ability to start heavy loads or what? Does your truck have a plate on the inside of the glove box door which lists the original equipment? Could you provide some pictures of your rear axle, differential and rear wheels?

I do have a 2 speed rear end 9.00 on the low side and 6.61 on the high side. Have installed a Brown-Lipe, and it helped.
Now in overdrive I am turning 25-2700 doing 55 MPH I would like to drop that to around 1500. The 454 pulls good at 2000-2500.
I can always down shift it to stay in the power curve.

Nice! You need to load that up with some classic iron.

That take money. Have just about depleted my Hotrod account doing this rig

There is a gentleman out of Guthrie, Oklahoma, who runs a towing company, that has an AD Cabover with a period transport trailer. He loads it up with 50-53 model Chevy cars, including a convertible, and takes it to the shows. Done over the top with fit and finish.

I replaced the rear in my ‘55 373 with a D-80 which has disc brakes to match front disc brakes I put on there. 5.13 ratio in it which I will change. Also have a Brownie in there. My bolt pattern is 5/10 on 7.25” so important to get same. You probably have same bolt pattern, so have to find that first. Those and similar rears come in two widths, about 7’ and about 8’ wide, depending on body style.

If you have a different bolt pattern, then D-70, GM ff 14 bolt would work. Then one has to get modern wheels and tires unless one wants to keep 20’s. 19.5’s are the only commonly available modern alternatives. Unfortunately they look undernourished compared to 20’s.

Some motor homes came with these axle/wheel combinations, need solid axle variety. Otherwise look in wrecking yards, dead roadside vehicles, tire shops for 19.5 wheels.

Good luck,

Ed