Swapping out to a 3.08 with a 30 inch tire diameter will net you about 2,400-2,450rpm. I don't know that you'd wanna go much higher than that. I'd think it'd turn your truck into a snail with a stock 327 in a big and heavy Chevy truck. It may even be a slug with a 3.08.
For a long time I thought I would just change out my ring and pinion for better cruising speed and that everything would be hunky dory. Turned out nobody made gears for the beefy 3/4ton rear (except Art Houser who makes a 3.90 for the lowly sum of $490) so I researched and researched and discovered the biggest gains were made doing a tranny swap with an overdrive unit.
Keeping your 3.73 and just swapping out to a .86 OD tranny gets you almost the same results as going all the way up to a 3.08.
Keep your 3.73 and swap to a tranny with a .72 OD and now you're at 2,100 rpm @ 70 mph.
I could be totally wrong about the 3.08. It might be great. Anyone else have thoughts on using a 3.08 with this setup?
-David
Kustoms-and-Sleds
