What should I look for to make better high-end gas mileage?

 

My thoughts as well....

 

if youre looking for gas mileage you have no need for a solid roller 350 in an s10 that is in need of traction bars. 3.73s are the next big step down from 4.11s, but if its a solid roller that was already built, the cam is probably going to get its most gains with a 4.10 gear. id find out what tranny is in there (maybe a th400?) and swap it with an a3+1 so you have an overdrive gear.

by the way what are your plans for the truck? daily driver or a race truck? thats the main deciding factor in what to do

 

I think the trany is a 700r? I'm not sure on whether to go all out on it, or keep it as a sport truck. All depends on how much in both directions.

 

well you need to decide that before you go spend an assload of cash on a new ring/pinion, install kit and posi + the install. its gonna cost you around $500 to go to a different gear if you do it right. thats not including a new posi unit.

 

Alright, with the gearing on the S-10 currently I would have really nice acceleration but I would top out around 120-130 and have horrible gas mileage. If I change the trany, rear end, posi, and all the bells and whistles, how much would that decrease the power (low end acceleration) of the truck? Would I then need to add to the current power to get the truck to accel. like it does now?

 

ok think of it this way. the rear end gear determines the ratio of how many times the tires spin relative to how many times the driveshaft spins. so by increasing that ratio (going from a 2.73 to a 4.11) you are going to limit your top speed, but decrease the length of each gear (ie youre in your motor's powerband more) if you decrease the gear ratio, you will increase your top speed (which is relative to gas mileage because you wont be riding at such a high rpm on the highway) but it will take longer to reach your peak power and get through that gear. one way to get around this is to use an overdrive transmission. if you switched to an overdrive transmission (4l60e, th700r4) you would have an additional gear that is meant for cruising.

if i was you, id swap trannies if your intent is to drive the truck everyday. if your intent is to have a wild track truck, leave the 3spd in there and spend money on a good stall.

 

All drag purposes, keep the 4.11's and get about a 3200-3800 stall converter.
For street/strip, get 3.42-3.73 gears and about a 2800 stall.
For a daily driver, get anything higher than 3.42's and a 2200-2600 stall.
That's considering you have about a 28" tire (275/60R15), the bigger the tire the higher the gear you can run and have the same RPM. If you have smaller tires though, you'd have to run a higher gear.

I'll be running a mild cam (~.500 lift and 220 dur), B&M Holeshot 2000 stall converter (on a TH350, probably move up to a 2800 stall later), looking for a 3.55 12-bolt GM rear-end (froma 68-72 Chevelle) and 275/60R15 tires.

 

A 700R4 or 200R4 won't hold up behind a built motor, if the trannies stock. Don't even bother with one...
Just get a TH400 or TH350 (the 350 is lighter, easier to turn and has better gearing... but it's a little weaker) and run a low set of gears and a decent stall converter.

 

yuck, built 4l60e. he'll be able to keep his driveshaft and the th400 robs over 40rwhp in most applications along with being heavy as hell and miserable on the road. th350 = cheaper alternative, but you can have a 4l60e built to withstand constant 10 second passes for $1,000