Inliners International Forums General Discussion Drive Train definitely not highway gears

i have a 64 3/4 ton with what i believe to be 4.56 (or close) rear gears. it still has a 292. i put a granny 4 speed in it. i like the gearbox, really don't want to swap out for a auto 4spd. so my questionis this, with my factory 4.56 limited slip gears, can i swap in a 3.73 or 3.55 with little modifications? i have looked at different sites for gears but haven't found an exact match to the diff. i am planning on really working on the truck this fall and winter. anyone have any idea or suggestions? thanks.

The question comes down to what rear end do you have. My 63 C20 has an Eaton rearend. The Eatons third member (pumpkin)drops out. If that's what you have the best gears your going to find are 3.93, very scarce. There are some 4.11 around. If you have the Dana you have a few more choices in gears. Though you'd probably find it cheaper to replace the complete rear axle with one from another C20 up to 72. This will do for a start I'm sure there are others that can add more info.
Larry

no dana here. that is kinda what i thought the response would be. i would like to keep the rearend.not sure if i like the options.

swap out the trans for a new venture 3500 5 speed manual od. it's used in S10's & full size 1/2 tons. or if you insist on having a granny low heavy duty trans. go with the nv4500 which comes in 3/4 ton & up chev. & dodge trucks. i believe theses trans. have a .68 od. with your 4.56 rear this would give you a final drive ratio of 3.10, excellent for highway use.
robert.