I think my truck has 4.10's

[Swearingsailor6]

Hey guys, well, I thought my speedometer was off, so I grapped my TOM-TOM Gps and set it to track my mph, and drove down the road and it is right on...so here are the specs

Unknown rear axle ratio, thought it was something like 3.08 or 2.73 but I think differently now. The truck I stole the tranny and tcase from has 4.10's.

SM465 4 speed with 1:1 3rd (4th gear total) NP208 with 1:1 2 hi, and my RMP's @ 55mph are something around 2400RPM if my tach is accurate, which I think it is. That equates to something around 4.10's in the rearend at least.

The truck came with a non-stock 12bolt rearend, so Im thinking they threw 4.10's in there when they put that in there?? I just wonder if they put 4.10's in the front end too....I can drive down a paved road in 4hi without any binding as long as I keep it strait....hmmm

let me know what you guys think.

[6 Pack]

Pull the covers and grab the numbers off the ring gear. Prolly a good idea to swap the fluid out and do an inspection anyways.

I could narrow it down for you a bit more...but I'd need to know your tire size..

Rene

[Swearingsailor6]

oh sorry, they are 31x10.5's, i used an online gear ratio calculator....I may pull the diffs this weekend depending on how the clutch goes in for my brothers truck

[6 Pack]

yep, looks like 4.10's. Good excuse to jump to 33's or 35's.

Rene

[modular93fox]

do an online search on this.
tire rotation to pinion rotation... this will tell you the approx ger ratio... i cant think of the exact how to, but its like number of tire rotation to 1 pinion rotation (or vice vera, which ever is more) is the gear ratio

[chubyboy]

ryan, put ur hands up... this here's threadjack...lol

but a quick, semi-related question, can you find ur gear ratio regarding the axle model numbers and the like?

[1979-350]

Originally Posted by modular93fox

do an online search on this.
tire rotation to pinion rotation... this will tell you the approx ger ratio... i cant think of the exact how to, but its like number of tire rotation to 1 pinion rotation (or vice vera, which ever is more) is the gear ratio

Heh, picture in your mind which gear is bigger, the ring or the pinion.

It's 1-turn of the wheel/tire to x.xx turns of the driveshaft.

[NovaMan]

Originally Posted by Swearingsailor6

SM465 4 speed with 1:1 3rd (4th gear total) NP208 with 1:1 2 hi, and my RMP's @ 55mph are something around 2400RPM if my tach is accurate, which I think it is. That equates to something around 4.10's in the rearend at least.

Tell us your tire size and we'll tell you your gear ratio. If you have 235/85R16s, or another tire that's about 31.7" tall, then yes, you've got 4.10s.

[6 Pack]

oh sorry, they are 31x10.5's, i used an online gear ratio calculator....

Rene

[NovaMan]

Oops, I guess I skipped over that post. Duh.