What rear gear do I have calculation

[Squareforceone]

I have an s10 that i'm trying to figure out my rear gear ratio without pulling the cover on. It's a 327 with a th350 at 60mph I'm running 2500 rpm my tires are 235/75R15's

[geezer#99]

Punch your numbers into here.
http://www.advanced-ev.com/Calculators/TireSize/

[Squareforceone]

What do I put for diameter ? Sorry for the dumb question

[geezer#99]

You guys really need to learn the metric system!! LOL!!
I'm still learning it after 40 years of it.
I'll give you the short answer, not the calculation.
Usually a 235 is 29 inches tall. Actually 28.87 inches by calculation.
Anytime you don't know a tire height, cross section etc just search for your size on tirerack. All the dimensions are there.

[jocko]

Calculates to a 3.55:1 rear, not exactly a common truck ratio - at least not for older trucks anyway. However, since you clearly don't have a stock setup and an S10 isn't "that" old, all bets are off - unless the 60 mph is from a GPS and not your dash (i.e. no way to know if the rear tire dia is stock to the rear gear/trans output shaft speedo gears, etc. If you do (or did) use a GPS, then it can be calculated more accurately. Below is for a TH400, but it shares the same 3rd gear final drive of 1:1, so it works for comparison. (I used 28.9" for the tire)

[Squareforceone]

Thanks everyone I didn't know a whole lot about the truck i just bought it. It's an 84 s10 with with a 67 327 a th350 they 60mph was from the speedometer but has been checked against gps for accuracy

[Keith Seymore]

Originally Posted by jocko

Calculates to a 3.55:1 rear, not exactly a common truck ratio - at least not for older trucks anyway. However, since you clearly don't have a stock setup and an S10 isn't "that" old, all bets are off - unless the 60 mph is from a GPS and not your dash (i.e. no way to know if the rear tire dia is stock to the rear gear/trans output shaft speedo gears, etc. If you do (or did) use a GPS, then it can be calculated more accurately. Below is for a TH400, but it shares the same 3rd gear final drive of 1:1, so it works for comparison. (I used 28.9" for the tire)

Based on this I'd guess 3.42 or 3.73.

Probably time for the "spin the driveshaft method" (or pull the cover).

K

[gmachinz]

At 60 mph with a 26" tall tire I was hitting right at 3K and those were 3.73's and I had a TH400 at the time. This was in a Monte Carlo I had at time.