spur and pinion combos

[Mozer]

I have a XXX-t with a 2.6 tranny. What is the best way to calculate the best pinion for each spur gear? I am running a stock motor. I saw on trinitys website that for a 48 pitch 86 tooth run a 22 tooth pinion. For the moster hp drop two teeth. I have a monster hp witha 82 tooth spur and ran a 21 pinion and obviously cooked the motor. how can i figure out which pinion to run with each spur with each motor. And suggestions would help.

[Graystar]

Just match the ratio.

Divide the spur size by the pinion size:
86/20 = 4.3

Just divide 82 by 4.3 to get the pinion size that matches the ratio
82/4.3 = 19.07

So you need a 19T pinion. The new ratio is actually:
82/19 = 4.316

The ratio you were running was:
82/21 = 3.9

...which is probably too low. Try to stay within +/- 0.2 of the recommended ratio. Don't go beyond that unless you're certain you need to.

[Mozer]

so how do you know what ratio is gonna melt you motor? i am assuming when trinity gives a suggested 86/22 gearing that is the recomended ratio?

[Graystar]

so how do you know what ratio is gonna melt you motor?
You review the manufacturers' recommended pinion size for the type of motor you have and then try to stay within +/- 1 tooth on the pinion. Add more than one tooth and you risk melting the motor.

The pinion recommendations should be in your manual. If you don't have it, you can probably download it from the car maker's website.

[Mozer]

Ok but what if you are not using the same size spur that is in the manual. Do you just use the same ratio?

[Graystar]

Ok but what if you are not using the same size spur that is in the manual. Do you just use the same ratio?
Yes. The ratio is what's most important. The actual size doesn't really matter.

[Mozer]

k thanks a bunch