ok need help, i am planning on putting gears in my rearend and here is what i need to know what rpm i will trap at with 4.30 gears 4.56 and 3.73 my shift point or right at 7200-7600 so i nned to know if i am going to trp to high or not and any other info you need to help me out i can tell you and it is a tremec tko 500 that is going ing the car with the 3.27 first gear and can you tell me what my top speed is going to be
rpm threw the traps need help
- Thread starter mustangrfast88
- Start date
Stang8URMPRT
Active Member
We need to know your rear tire size... gimme all of them.. like 275/60/15.
Based on that size of tire you would trap (theorticall of course) in fourth (1:1 ratio) at 166 MPH with 3.73s at 7200 RPMS... 4.30s..139 MPH... 4.56, 131 MPH
Nick
Based on that size of tire you would trap (theorticall of course) in fourth (1:1 ratio) at 166 MPH with 3.73s at 7200 RPMS... 4.30s..139 MPH... 4.56, 131 MPH
Nick
rd
Founding Member
Might as well do the math. Heres one way.
There are 5280 ft/mile. A 26 in dia tire is 2.1667 ft in diameter and 6.801 ft in circumference, so it turns over 775 times per mile. So at 60 mph, which is a mile a minute, the rear tires are turning 775 rpm. The engine rpm is the tire rpm times the axle ratio times the trans ratio, if you have overdrive.
So for a 4.10 gear, no od, 775 x 4.10 is 3180 rpm for the engine at 60 mph.
So the tire rpm at 7000 engine rpm is 7000/ratio, or 7000/4.1 is 1701.
1701/775 is the same as new mph/60, so 60x1701/775 is 131 mph.
Easiest to just do a spreadsheet and try combos.
Generally gear the car so that your finish line rpm is at or just under your planned max rpm.
There are 5280 ft/mile. A 26 in dia tire is 2.1667 ft in diameter and 6.801 ft in circumference, so it turns over 775 times per mile. So at 60 mph, which is a mile a minute, the rear tires are turning 775 rpm. The engine rpm is the tire rpm times the axle ratio times the trans ratio, if you have overdrive.
So for a 4.10 gear, no od, 775 x 4.10 is 3180 rpm for the engine at 60 mph.
So the tire rpm at 7000 engine rpm is 7000/ratio, or 7000/4.1 is 1701.
1701/775 is the same as new mph/60, so 60x1701/775 is 131 mph.
Easiest to just do a spreadsheet and try combos.
Generally gear the car so that your finish line rpm is at or just under your planned max rpm.
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