Help calculating RPM

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Baker7888

G-Body Guru
Dec 3, 2021
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Maine
Hey guys was hoping someone could help me calculate RPM based on speed for my setup which is a close ratio T-10 4 speed (cast iron 63 vette) with a 4.10 rear and a 26.5” tire

I am looking for what RPM i will be running at 70 mph in 4th gear. I have this setup now (speedometer incorrect) and regret my decision on gears. Thinking of going to a 3.23.
 

Baker7888

G-Body Guru
Dec 3, 2021
665
115
43
Maine
Spoke too soon i guess. Looks like spicer has a calculator. I think 4th on a t-10 is 1-1?
If thats the case then with a

4.10 at 3000 rpm equals 58 mph
3.23 at 3000 rpm equals 73 mph

Does this look correct?
 

scoti

Royal Smart Person
Sep 5, 2019
1,959
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Texas
Spoke too soon i guess. Looks like spicer has a calculator. I think 4th on a t-10 is 1-1?
If thats the case then with a

4.10 at 3000 rpm equals 58 mph
3.23 at 3000 rpm equals 73 mph

Does this look correct?
Yes. Looks correct.
 
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Streetbu

Know it all, that doesn't
Supporting Member
May 22, 2011
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You'll hate 4.10's for anything other than 0-60 full throttle runs, and 30mph cruising. Unless you had overdrive which you don't. I wouldn't go any higher numerically than 3.42, 3.23 would be a decent choice too.
 
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Baker7888

G-Body Guru
Dec 3, 2021
665
115
43
Maine
You'll hate 4.10's for anything other than 0-60 full throttle runs, and 30mph cruising. Unless you had overdrive which you don't. I wouldn't go any higher numerically than 3.42, 3.23 would be a decent choice too.
Ya i ordered 3.23. Didnt think the 4.10 would be as bad for some reason
 

Baker7888

G-Body Guru
Dec 3, 2021
665
115
43
Maine
Taller tires would take some rpm out of the total but not by much.
Good idea. I have a pair of 295/50/16 at about 28.5" tall but they are too wide And will scrub the frame
 

565bbchevy

Geezer
Aug 8, 2011
9,590
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Michigan
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