Re: "Crawl ratios" and calculating same

[tsm1@domain.elided (Tom Mandera)]

>All this talk about "crawl ratios" has me wondering how to calculate them.
>I have a '65 T'all, with what the line setting ticket calls the T-16 (it is
>a 4-speed, with a 6.8:1 (or close) 1st gear) transmission, a transfer case
>that I don't remember, and 4.09 differentials.  So, do I just multiply the
>ratios to calculate a final ratio?  Is there a table I need to use?  There

Yep.  So for you, 6.8 1st gear * 2:1 low (OK, NP205 is 1.96), * 4.09 gears =
about 54:1 crawl or final drive.

>must be some effect of tire size on all of this.  Can anyone post a (brief)
>tutorial, or point me to where I can find the answer?

Tire size has a big effect... a 54:1 crawl with 31" tires is slower (and
thus, more grunt) than a 54:1 crawl with 44" tires... 

But, two trucks with 33" tires, one wiht a 54:1 crawl, one with a 60:1
crawl, and the 60:1 is slower, and has more "power".

Factoring in tire size gets into "effective" gearing.. and it can get a bit
interesting, particularly when you factor in "airing down" the tires and such..

-Tom