Help with gear ratio please

[tawd77]

I have an 81 Chevy short step 2wd that I just did a 5.3l/4l80e swap in. I think the truck has 2.73 rear gears right now(originally a I6 250/Th350). 235/75r15 tires. It is running around 1800rpm at 75mph.

What would be a good gear ratio, for a mix of city, highway, and towing trailers? The 2.73 has no take off power, and seems fairly gutless pulling a trailer. I was thinking a 3.42 might be about right, but I dont want it spinning too many RPM down the highway, killing my fuel mileage.

You guys have any suggestions for my setup? Thanks!

[Rattler12]

3:73's would get you back down to effectively 2:80 when in OD  plus would be great for the low end power and acceleration. I've got an NV 4500 5 speed in mine with 3:73's and at a .73 OD it's equivalent to 2:72 's

[tawd77]

Thanks for the info. I am trying to decide between the 3.42's and 3.73's... Decisions decisions...

[Captain Swampy]

Search for gear calculators. Go out and measure your tires for the correct diameter. Real world measurement makes a difference.

[84c10tony]

I had a similar situation, 84' short ss, oe 2:73's, have a set of used 3:42's, but, after research and speaking to the good "go to guy" Robert Thomas Differentials in Hesperia, Ca, he put in a Detroit Tru Trac and 3:73's, all new bearings etc.
I told him I was going to 235/75/15's, with all around driving, hills, trailer etc...after install, got 18 mpg with a 5.0/700R4 on 225/70's keeping a light pedal.

[Captkaos]

I am running 3.42's in mine behind a 4L80E.  I think it is a good combination.