The Stovebolt Site Forums The Shop Area Engine Shop 56 GMC axles/od's?

I have a 56 GMC with Hydramatic and the Pontiac v8. I understand the rear end ratio is 3.9 to one. It looks like the diff is either a GM ho33, or a Spicer 45. How can I tell the difference? So far I can see these options for a better road ratio: change the gears in the diff, put in a o/d auto transmission, chamnge the diff, or add a gearvendors o/d. Anyone have a suggestion of an axle down abt 3.31 or so? Thanks. Bob KNOTTS

welcome to the 'bolt Bob! we always like to see more of the 5-9 trucks here
if it's basicly the same rear as the Chev [should be] there's 3.38 gears made - Patricks [near you] will have'em or a good rear-end shop - spendy tho, prolly a grand all in - should be an OD trans that would pretty much bolt in -I can't name it, but someone here will know

Bill

Those old pont. v-8s had there own bell housing & flywheel bolt patterns. It would be hard to change trans. without going to a latter engine. I would change the diff. ring & pinion to the 3.38. I put one in a 56 a while back. Ive been a mechanic for 55 years but I think a guy with good mechanical instincs could do it with the instruction sheet that comes with it & a manual or 2. Plus you have the Stovebolt websight to help.