Hey guys I’m been contemplating doing a ring and pinion swap in my ‘86 Chevy C20. This truck guzzles gas like nothing I’ve ever seen before. I’d be literally surprised if it got double digit hwy fuel economy.

The truck has a 350 V8 mated to a TH400 (no overdrive) with 4.10:1 gearing. My calculations say that at 100km/h (62mph) the truck would rev 2810 RPM. If I swapped out the gears to 3.42:1 (lowest numerical availble for 14 bolt rear end) it would drop my RPM to 2343 RPM. This is a 17% in RPM How much do you think this would improve fuel economy? 2-3 mpg or more?

I don’t use the truck for any heavy towing or anything so I’m not at all concerned with the lesser pulling power. I just don’t want to spend $30 bucks in gas everytime I drive the truck.

I not doing a tranny swap or putting in a gear vendors overdrive(I would really like the latter though) so don’t even mention it.