Quick question about speedos, confused.

[SwaintaN]

ok the VSS is local i found one 20.00 2yr warranty; thanks on that one!

ok so since 19 tooth gear seems kind of high for stock.. how do i go about figuring this out now... lol just wanna drive haha.

 

[SwaintaN]

someone check my math really quick i tried following manics example from earlier...


apparently i have a 19 tooth gear, 235 to 33 is a 11% increase.. so 19 + 2.09 so 21.09 tooth gear so a 21 tooth gear is what i need!?! is that right hahaha so cluster fd right now

 

[SuRrEaLNJ]

7 teeth on drive (assumed)
3.73 ratio
33x12.5x15 = 636 revs/mile

(Drive Gear Teeth x Axle Ratio x Tire Rev. Per Mile) / 1000.

(7 x 3.73 x 636)/1000
(16605.96)/1000
16.606

so unless my math is off your between
16 __________Maroon___C0DZ-A (C0DZ-17271-A)
17 __________White____C3DZ-C (C3DZ-17271-C)

 

[SwaintaN]

so i would down grade from 19 to 17?

 

[Maniak]

How big is the tire?

225x70r15 like posted a few posts ago is only 27.4" tall
a 33" tire is more like 32.5
a 235x75r15 is 28.8" tall

From 27.4" tire to a 32.5" tire is an 18.5% change
From 28.8" tire to a 32.5" tire is an 13% change

Soo.. if it was a 27.4" tire then you need a 22.5 gear tooth. I'd error on the fast side.. smaller gear.

If it was a 28.8" tire then you need a 21.5 gear.. again.. I'd err on the fast side.. get the 21 tooth

It appears you did the math correctly assuming you had a 235x75 tire and not a 225x70.

~Mark

 

[SuRrEaLNJ]

i used that equation when i did mine.

7 teeth on drive (assumed)
4.88 ratio
35x12.5x15 = 598 revs/mile

(Drive Gear Teeth x Axle Ratio x Tire Rev. Per Mile) / 1000.

(7 x 4.88 x 598)/1000
(20427.68)/1000
20.42768

i rounded that up and went with the red 21 tooth gear.

i think im actually closer then my focus with the stock size tires on them.

when i did the math strugled wraping my head around the equations, pluss the truck had been off the road for 2 years, so seeing how far it was off wasnt the way to go either. so i used the equation where i wouldnt have to know anything prior and could start from scratch. so yes, by my math you need less teeth

 

[SwaintaN]

yeah there was the 235s on it when i got it.. is the 19 tooth gear kind of high for a stock gear?

 

[SuRrEaLNJ]

although i should point out i failed out of math in college

 

[Maniak]

umm.. hang a sec.. I think I did the final math backwards....


Changing the tires to bigger tires makes the speedo read slower.. To get the speedo to read faster we need to put on a SMALLER gear...

Soo.. with a 225 tire you should have a 15.5 tooth
with a 235 it would be 16.5 tooth..


~Mark

 

[SwaintaN]

ahhh lol, so i need to down grade from 19 tooth to a 17 tooth cause i went from small tire to a bigger tire?

lol i labeled this one right, confused! rofl

clarifying.. 235 tire to 33" tire... means my 19 tooth needs to go to a 17 tooth?

 

[SuRrEaLNJ]

well atleast i know i wasnt way off then

 

[Maniak]

ahhh lol, so i need to down grade from 19 tooth to a 17 tooth cause i went from small tire to a bigger tire?

lol i labeled this one right, confused! rofl

clarifying.. 235 tire to 33" tire... means my 19 tooth needs to go to a 17 tooth?

Correct. 17 tooth is about as close as your gonna get. How close to 32.5" your new tire is will determine how close your speedo is now.

~Mark

 

[SwaintaN]

ok ordering 17 tooth now for my newish 33s and going tomorrow get a new vss thanks guys!

 

[LXNavajo_94]

I only paid 9.95 for my gear at the local dealer and thought that was just for one gear picked up the part and lo and behold there were 2 gears in the bag.

 

[SwaintaN]

hey I know this is old and kind of dead.. but Maniak youve helped me a lot!

so new question in this area.. dont wanna start a new thread...

Im getting ready to change 3.73 to 4.10, still same tires etc, will I need to change the speedo gear... or does the axle gears not bother speedo gears?

Thanks guys!

 

[Maniak]

hey I know this is old and kind of dead.. but Maniak youve helped me a lot!

so new question in this area.. dont wanna start a new thread...

Im getting ready to change 3.73 to 4.10, still same tires etc, will I need to change the speedo gear... or does the axle gears not bother speedo gears?

Thanks guys!

If all you change is the gear ratio then yes, you need to change the speedo driven gear. You need a driven gear that is 10% larger to slow down the driven gear.

Edit: I had the right numbers but posted what to do and why wrong. I had "change tire size" on the brain.

When you go from 3.73 to 4.10 your speedometer is going to read fast. You need to slow down the speedomter. In other words, your speedo will show 60mph but you'll only be doing 54 mph.

~Mark

 

[SwaintaN]

If all you change is the gear ratio then yes, you need to change the speedo driven gear. You need a driven gear that is 10% smaller to slow down the driven gear.

~Mark

so 15.3 gear? since its not above .5 go for the 15? wonder how much this will throw off the dash

just to verify 15 correct?

your awesome!

 

[Maniak]

so 15.3 gear? since its not above .5 go for the 15? wonder how much this will throw off the dash

just to verify 15 correct?

your awesome!

I fixed my post above.. (I had change tire size on the brain instead of change gears).

What size driven gear do you have now? If you have a 17 tooth driven gear (taken from a post above) now you want a 19 tooth when your done. That way when your doing the 54mph your speedo is going to show 53ish. That is about as close as your going to get.

If you go with an 18 tooth driven gear it will show 56mph when your doing 54mph as it will always read 5% high which "might" be a good way to keep from speeding .

~Mark

 

[SwaintaN]

I fixed my post above.. (I had change tire size on the brain instead of change gears).

What size driven gear do you have now? If you have a 17 tooth driven gear (taken from a post above) now you want a 19 tooth when your done. That way when your doing the 54mph your speedo is going to show 53ish. That is about as close as your going to get.

If you go with an 18 tooth driven gear it will show 56mph when your doing 54mph as it will always read 5% high which "might" be a good way to keep from speeding .

~Mark

Ok I have 3.73 w/ 33s now. I went from stock 19 teeth stock tires, to 17 teeth w/ these 33s and the 3.73 per earlier math. Keeping same 33s but changing to 4.10 gears.