Picking rear gears

CaliWagon83

CaliWagon83

Royal Smart Person
Supporting Member
Nov 12, 2017
1,652
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Orange County, CA
#13
Well, I’m coming from the context of 26” tires. 29” tires change (lower) the overall RPMs.
 
olds307 and 403

olds307 and 403

Comic Book Super Hero
Oct 14, 2008
3,777
1,648
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Melville,Saskatchewan
#14
airboatgreg

airboatgreg

Royal Smart Person
Oct 2, 2016
1,340
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#16
I just did this and I put a 3:70 to pair with my Muncie 4 speed. I drive 60 miles a day to work and back but my car is not a daily driver. I went from a about a 2:80 stock and it made a new car out of it. What do you want? Mileage, performance? You have overdrive so that is a plus. Hard to beat a 370ish gear but with OD you easily can go a 342ish.
Do you drive in a hilly area? Downshifting an issue? or is terrain flat? Gas is relatively cheap now but I expect it to increase so that may be a consideration.
 
MrSony

MrSony

Comic Book Super Hero
Nov 15, 2014
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Des Moines, Iowa
#17
At 75mph with my 26.1 tires and 3.42s I'm at 3300rpm, and it's not bad, sound wise, but it's annoying and puts unnecessary stress on an otherwise low strung engine. .67 O/D of a 200r4 would put it at 2200. Much More livable.
29.2" tire, .67 O/D, 4.30 at 75mph calculates out to 2486rpm for this calculator. Always been accurate +/-100 rpm for me.
https://www.crawlpedia.com/rpm_gear_calculator.htm
 
Texas82GP

Texas82GP

Comic Book Super Hero
Supporting Member
Apr 3, 2015
4,518
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Spring, Texas
#19
I calculate 2790 RPM at 85 assuming 0.67 overdrive (please confirm), 29.5" tires, and a 4.30 rear gear. I think that's about right. My daily driver turns 2500 at 80 and 3000 at 95. It's a truck with 4.11 rear and nearly 32" tall tires (275/55/20). It has a 3400 stall and I mush it down the highway at 85+ with no issues.

2.74x4.30=11.72 final drive ratio in first, seems steep but that really tall tire will mitigate it. Looks like a reasonable setup to me.
 
565bbchevy

565bbchevy

Geezer
Aug 8, 2011
5,824
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Michigan
#20

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