How to make highway speeds?

Hi everyone..

I have a 1965 c36 1 ton that has no problems moving around town with it's 6 cyl and 4 speed with granny gear.

How can I make it operate better for highway speeds? Currently 55 mph seems to be pushing it..

Thanks in advance ..Russ

 

Hey Russ,

You've probably got a 4.57 rear end ratio or higher, if you brought that down to a 3.73 or 3.30 you would be able to cruise at highway speeds without feeling like the pistons are going to come through the hood. I went to a 3.08 with a granny low 4 spd and it worked fine except that I had very little torque in 4th and wasn't really happy with it.

 

Hey BK65..

Thanks for the information. It sounds like you know what I am taking about. How did you get the different ratio? Is there somewhere on line I can go to or could my local transmission shop help out?

Also.. I should look at the 3.30 ratio as it sounds like you are not pleased with the 3.08 ratio. Let me guess.. in 4th gear, you hit a hill and lose most of you speed..

Thanks again for this valuable information.
Regards, Russ

 

Russ,

I only pretend to know what I'm talking about

Changing the rear-end ratio could be as simple as changing your ring and pinion gears, or you might have to replace the enitre differential.

It also might be easier to just replace the rear axle with a more modern one. That's what I did on my old truck. It was cheaper to get the whole axle (at the local salvage yard) than it was to get new gears. A lot of the later Chevy 3/4 ton rear ends can be found with the 3.73 gears.

If you can find out what rear axle you have (GM, Dana, etc) your local tranny or driveline shop could answer more specific questions.

I hope this helps and I'm sure you'll get more responses with more helpful info.

 

you could try a different tranny if your interested in going that way. the newer 4 speed automatics have a lower 4th gear that would compensate for your rearend gears. i'm having the same problem and was thinking of going that way. my 39.5's don't seem to help.

 

Hey AJ..

Thanks for the info.. I was also told to get taller tires in the rear which will help a little.

Thanks again..
..Russ