1970 GMC 1/2 to Tranmission question

[2guns]

I have a 1970 GMC 1/2 ton with 4 on the floor, first gear is very low start off in 2ed. 4th gear is a bit too low for me top speed is 60 it can go faster but the rpm is too hig for my taste.. would like to know if there is another trans i can drop in that can give me more of a freeway range? i do not go fast but i would like to be able to cruz at 65 to 70 without winding out the engine. it has a 292 in it and i have no plans to change that i like getting 15 mpg, thx JD

[Palf70Step]

Welcome to the board. Yopu proabbly have what is called a granny low.

However, unless you go with an overdrive automatic, 4th gear is a 1-to-1 ratio, like D is on any non-overdrive tranny.

It sounds like you may have a 4:11 rear end or lower (4:56 maybe). For mostly highway use, I would see about changing the rear gears to a 3:07 before I would go thru a tranny swap

[2guns]

yes i have a possi 411 ill look into the rear end. thx

[luvbowties]

Originally Posted by 2guns

yes i have a possi 411 ill look into the rear end. thx

Hey 2guns, as others have posted before, tire-height-change is another option and can have the same effect as gear-change.

Tire change is not only quicker, but often cheaper. Plus it would enable you to keep your 4.11 posi as is, changing speedo gear(s) to correct the speedo. As I understand it, 3.73 would be the lowest ratio, numerically, that would fit in your present housing, and that may not be enough.

Tire-height-change offers a pretty much continuous choice of height change, whereas gear changes are number-specific and give only distinct choices, jumping for example-only, like from 4.11 to 3.73 to 3.42--with nothing in-between.

HTH,
sam

[2guns]

Thats a good idea, thx