'67 c-20 4x4

[ChrisWhewell]

Picked up a '67 C-20, factory 4-speed & factory 4X4, V-8 couldn't resist.

Its geared so low though, that highway driving is out of the question, I'm guessing the engine's turning 3,000 rpms when going 45 mph. SM-420 with 4th at 1:1.

Mulling over getting a 2.5 - 3.0 axle ratio in it and swap the trans so high gear will be 0.5:1 at the trans, so I can go 70 mph on the highway with engine only turning approx 1500 rpm.

But, I suspect I'd need to swap out some gear in the transfer case too, but I don't know squat about this. I'm thinking it will still be good as a work truck & around the town driving b/c of the creeper gear. Any thoughts muchly appreciated. Thank you.

FWIW, my 93 vette has 6-speed with 0.5:1 6th gear and 3.07 rear end and gets 28 mpg highway. The C-20 only weighs 500 lbs more and I'd expect to get at least 22 mpg on highway with it if it were similarly geared. I know tons about engines but little about gear swaps.

[ChrisWhewell]

Checked the tag on the front diff., says 4:55.

Tire dia. is 30.5 so in 4th gear engine is turning 3012 rpm @ 60mph.

3.08's would take it down to 2038 rpm & I'd expect significant fuel savings then.

[bundeber]

you won't have to touch the transfer case. Just make sure to swap out both front and rear ring and pinions. NOTE, your speedometer will probably be off after that.