There are two options for a rear end swap on 3/4 ton trucks from '47 to '72; one is to do a "chuck swap" of the whole front assembly, and the other is to buy one of the newly manufactured 3.90 gear setups from any of the old truck suppliers which we are not longer allowed to post here as it violates the "no selling/no commercial reference rule" of the Stovebolt forum.
The stock setup is either a standard 4.57:1 ratio, or optional 5.14:1 stump puller. Dropping to a 3.90 or 4.10 is an obvious improvement of up to 20% depending upon what you use and what you had to start with.
The two options that I know of are using a rear out of any GM '67-'72 3/4 ton w/AUTOMATIC (coil spings) rear end which is either 4.10 or 4.11 depending and is a bolt in and easy, or using the 3.90 rear gears that are manufactured and are a more involved and time consuming ring and pinion swap.
Soooo...
Here's a link to doing a 3/4 ton rear swap which is on my website.
3/4 ton Rear End Swap 1951 GMC This data was posted here on Stovebolt but it was purged (when the bathwater, baby, tub, and bathroom were thrown out a couple of months ago) in an effort to manage file size issues with the Stovebolt server. I voiced my disappointment with this at the time and have since redone the information in abbreviated form on my website where we warn before deleting valuable data to give you a chance to save the data! Bitter?...moi?...why do you ask?
Recognizing this be a violation of the rules, here's the link to the source of the ring and pinion source as well as the swap page on my site:
Art Houser\'s I believe that
Jim Carter and
Chevy Duty sell these ring and pinion sets also.
