The Stovebolt Site Forums The Shop Area Driveline 1st timer wanting to upgrade a 1955 1st Series rear axle

I am new to these trucks. Just bought a 1955 1st 261 and want to raise the differential gears. Possible to something in the low 3s. Looks like a 10 bolt but when I look a the internals on line for the 10 bolt they looks very different from what I am seeing, ie the adjusting nuts etc. Can anyone help and is this change beyond the capabilities of someone with only moderate skills?

I can't tell what , by name, differential I have or if it is original, certainly looks to be.

BarryP, First off Welcome to Stovebolt! From your description it sounds like your new to you truck already has some mods from original so it's not possible to give you much advice without seeing what you actually have for an existing rear axle. To help folks help you, take and post some pictures of your axle in your thread (and any identifying info you can find) using the guidance found in this helpful How-To guide.

Looking forward to further info and pics so we can offer some help.

Looking on line for info, you are probably getting info for a GM Corporate 10 bolt, which is generally 1970 and newer; maybe not what you have in your '55.1. Go to GM Heritage website (link below) and find your truck year/model, where you can download the correct "vehicle information kit". That will show you where to find you rear axle casting numbers, which will tell you what rear axle you have, assuming it's original. If not original, then look online for GM 10 bolt identification charts and go from there.

https://www.gm.com/heritage/archive/vehicle-information-kits

This link has service manual info which could help identify what you have also.

https://chevy.oldcarmanualproject.com/

Hi Barry,
Just FYI, I would take a look at what sort of transmission you have (particularly the gear ratios) and then we can try to help with what you're hoping to accomplish. I have a T5 (five speed) out of a GM van (Astro van or Safari van) made in the late 80s. The ratio chain starts with a first gear of 4.03 to 1 so it works very well with a 3.07 rear end out of a 1969 Chevy pickup (a 12 bolt rear). If you have the stock transmission, the first gear might be 2.94 to 1 and with a rear end in the low 3 range, you might have trouble. Most pickups with six cylinder engines relied on a 1st gear overall ratio around 12. That would allow you to load 800 to 1000 pounds of "stuff" in the bed and drive normally...well, as normally as possible with the steering and braking scheme we have. As for your question, no...this isn't beyond your ability. It will require some study and thought. There is a great wealth of knowledge here and the folks are happy to help.

Thank you all!

I'll post the other info in a few days.