Does anyone know the gear reduction ratio(s) for the diff

[ShiftPoint]

Hi,

does anyone know what the gear reduction ratios for a stock diff's are, actually I need to know them for the diff's on stock diff's on a rtr and a SS X version 4.6?

Even better would be how to get the ratio for them, I am not even sure which gears to use in the calculations?

I need these to set the speed reading setup in my radio.

thanks for any help!

John

 

[Crash]

stock is 14.61:1 when using 17/49 gearing

 

[ShiftPoint]

I think that is for the spur (transmission gear) and the cb, correct?

I need the radio for the gears in the diff, I am wondering if the spider gears effect the radio, or is it just the other 2 gears in the diff.

I have the tach mounted on the front side of the transmission (between the transmission and the front diff.

I guess I will see if I can get down low enough to count how many turns of the dogbone to a distnance. I just thought of something, maybe I can get a reading off of the tach.

thanks crash

 

[Crash]

 

[CrawlinClodKiller]

Diff=43/13=3.30 That is ring rear divided by pinion. To get the final ration though you have to add the spur bell combo in to. So say in my case 49/18=2.72. Then you multiply them 3.30x2.72=8.98. Than you have to multiply the tranny. Ratios here https://www.hpisavageforum.com/forums/showthread.php?t=3322&highlight=tranny

So with a 2 speed in first it is 2.44x8.98=21.9. So in first gear with a 2 speed tranny the above spur bell combo the crank will turn 21.9 times for every rotation of the tires. However you also have to add in the tire size to get an acurate speed. Smaller tires have a lower gear ratio than taller tires just like gears. For instance if you have 8 in tall tires you can't accelerate very fast, but you have higher top speed. With 4 in tires you can accelerate faster, but have a lower top speed. The radio system will not be totally acurate because of all this other stuff but It can be programmed close. I hope this helps you some.

 

[ShiftPoint]

thanks,

good that means I did it right, I figured it was the 43:13, so to get how far the truck moves with 1 turn of the axil I took the tire dia x PI to get the distnance the tire travelles in one rotation of the tire (circumfrence) took that x 13/43 and that gives the distnance the tire moves in 1 rotation of the axil.

I feel better now that you posted the same thing I did.

thanks

 

[CrawlinClodKiller]

I messed up on the math. I editting my post to fix it though. Now it is the way it is supposed to be.