77 1/2T Chev w/TH350 and 12-bolt. I am running 35's and am re-gearing for towing. I was going to go with 4.88's but it looks like the RPM will be a little high at cruising speed. Should I use 4.10's in it? I will be towing a light trailer and about a 3200lb rig. What is your experience with towing with this set-up?

With 35's and your average bolt-on modded small block, you'll wish you'd gone higher if you're going to primarily use it as a tow rig. Throw 4.56's in and call it good. You'll be a little under 3,000 rpm at 65 with your actual tire diameter and your tranny will stay cooler and live longer. The extra RPM you turn won't waste anymore fuel than your motor laboring harder 3 or 4 hundred RPM below that with 4.10's.

I think I'd be happier with 4.10's. The 4:56's will be revving a bit more than necessary unless you have a 7500+ lb trailer.

Jason :)

Why would you want that tall of a tire on a towrig? Cuts the power and makes the truck unstable due to the flex in the sidewalls.

JMHO, put some 235/85s (hair under 32" tall) or similar on it and you will be much happier.

I use to tow with 4:10's and 33" tires with my 1980 k20 with a GM reman with a mild cam and it worked great. I would think that 4:56 and 35's would be okay.

35's are just because I have them right now. I picked it up for $1500 and right now it has brand new 33" Thornbirds...YIKES. What sucks is I can get 4.10's for free and Yukon 4.88's with masters for $200 (that's $200 for front and rear). Of course 4.56's are not available at a decent price right now...

I'll be running 35" MTRs so I think those will be ok towing. I am staying away from any metric BS with rim sizes other than 15"

When I towed with my old Z-71 (5.7 w/Vortec), i never put it in OD (of course)... It ran around 3k in 3rd (1:1) with 265/75/16's at freeway speed. Out of curiousity I let it pull in OD during a Havasu trip (very flat trip from Phoenix). Boat tugged at the truck noticably more and the mileage was worse. Just my personal experience.