Spur gear

[REVOJACKSON]

Hey,my spur gear just went out and i was wondering what would be the difference between 38 & 40 teeth.thanks

 

[itsalifeworthliving]

the 38 will give you more top end and less torque the 40 will give you more lower end torque with less top end.

 

[REVOJACKSON]

So a 36 teeth would be more top end

 

[cptvkirk]

When in doubt, check the book

If you have the manual for your revo, go to page 43 i think and it should have a pretty good break down on the gear ratios for various spur/pinion combos as well as the ratios for the various xmsn gears.

Take note of the factory ratios (indicated in red with an asterix)
If you run a 15t pinion with a 38t spur and wide ratio tranny, you'll wind up with a 15.22 final drive ratio. as in engine turns 15.22 times vs 1 rotation of the tires.
If you keep that same tranny and decide you want to change your gearing and go with a 16t pinion and a 40t spur you'll change to a 15.02 final ratio...not much of a change at all.
Larger pinion...taller final driver, smaller spur... taller final drive.
There are trade offs. If you want a top speed screamer that would explode on impact a 17t pinion, with a 36t spur and wide ratio tranny should land you at a 12.72 final ratio. Want to have some fun math....figure your peak engine rpm multiplied by the final drive ratio times the circumferance of your tires and you can ball park your top speed..keep in mind circumferance will change with increased tire speed.

Also, the more you gear for top end the more you sacrifice launch capability.

I haven't seen anything for changing the diff gears yet and would probably be a p.i.t.a. but tranny, pinion and spur gears are by no means expenisive giving you the ability to try several combinations to see what works for you.
If you just want to race your buddy down the block. drop in the 17/36 combo. he'll probably pull you off the line but you'll catch up quick enough. If you are playing in tight areas, you may want a closer ratio gearbox with shorter spur/pinion combo's to get you that quick launch out of the corners or short approaches for jumps, nevermind the inevitable wheelie fun.

YEEAYYY, i think this might be my first plus rated post!!!

 

[cheeseball01]

If you have the manual for your revo, go to page 43 i think and it should have a pretty good break down on the gear ratios for various spur/pinion combos as well as the ratios for the various xmsn gears.

Take note of the factory ratios (indicated in red with an asterix)
If you run a 15t pinion with a 38t spur and wide ratio tranny, you'll wind up with a 15.22 final drive ratio. as in engine turns 15.22 times vs 1 rotation of the tires.
If you keep that same tranny and decide you want to change your gearing and go with a 16t pinion and a 40t spur you'll change to a 15.02 final ratio...not much of a change at all.
Larger pinion...taller final driver, smaller spur... taller final drive.
There are trade offs. If you want a top speed screamer that would explode on impact a 17t pinion, with a 36t spur and wide ratio tranny should land you at a 12.72 final ratio. Want to have some fun math....figure your peak engine rpm multiplied by the final drive ratio times the circumferance of your tires and you can ball park your top speed..keep in mind circumferance will change with increased tire speed.

Also, the more you gear for top end the more you sacrifice launch capability.

I haven't seen anything for changing the diff gears yet and would probably be a p.i.t.a. but tranny, pinion and spur gears are by no means expenisive giving you the ability to try several combinations to see what works for you.
If you just want to race your buddy down the block. drop in the 17/36 combo. he'll probably pull you off the line but you'll catch up quick enough. If you are playing in tight areas, you may want a closer ratio gearbox with shorter spur/pinion combo's to get you that quick launch out of the corners or short approaches for jumps, nevermind the inevitable wheelie fun.

Damn, that was good. Very well put.

 

[cptvkirk]

Damn, that was good. Very well put.

Thanks!

 

[cheeseball01]

I gotta do it....

Hey,my spur gear just went out and i was wondering what would be the difference between 38 & 40 teeth.thanks

Two Teeth

 

[flandersander]

yeah. 40-38=2. But the answer you're actually looking for has already been said.

 

[cptvkirk]

I gotta do it....




Two Teeth

 

[cheeseball01]

yeah. 40-38=2. But the answer you're actually looking for has already been said.

Sorry, I tried to resist, but I just couldn't do it. Is that bad?

 

[wildone454]

while talking about spur gears , whats the easiest way to straighten out one that got bent while running, teeth are still great and i usually run all metal both Cb and spur

 

[cptvkirk]

if you have access to a body hammer and dolly set, or just a nice flat hard surface and flat hammer, you may be able to carefully tap the whoopie back out of it. Typically, this is not something you do and succeed at the first time but it may work for you. Just tap very lightly at first, watch for what is moving if anything at all and slowly work it back straight. Don't just lay it on something flat and drop a sledge on it.