speedo drive gear

[docgab]

Hello all,
So I was trying to order a speedo drive gear for my 78 K5, th350, np203. As soon as i call up they ask me "color code/number of teeth?" I have no idea. My t-case doesnt have a speedo gear right now so i have no idea what to order. I have 4.11 ratio in the back and am running 35 inch tires. I called an auto parts store and the chevy parts desk and neither could tell me which i needed. Can any of you gurus help a guy out? Thanks.

 

[pauly383]

Buy gears here http://www.tciauto.com/components/speedometer_gears.htm As for what gear to buy , I only know how to find that for 208's . But I will search and find out for older trucks IF I can

 

[scrappyk5]

you can change colors not only as what gear ratio , but also what size tires you have on. since yours did not have one in it, you might have to buy a couple different ones. they are not that expensive.

 

[k5floyd]

i think it would involve knowing the engine rpm, what gear your in, axle ratio, and tire dimeter and/or circumference to find what rpm the tire is turning. but from there im not good enough at math to figure the rest out

 

[k5floyd]

and pauly383k10, i know a bunch of math to find what drive and driven gear you need given you had a previously accurate speedo(which would require the drive and driven speedo gear) but if you know any easier way, id like to hear it, as i have a 208 and changed gears and tires, and my speedo is now way off. thanks

 

[docgab]

Hey, thanks for the input all. It is much appreciated!

 

[pauly383]

and pauly383k10, i know a bunch of math to find what drive and driven gear you need given you had a previously accurate speedo(which would require the drive and driven speedo gear) but if you know any easier way, id like to hear it, as i have a 208 and changed gears and tires, and my speedo is now way off. thanks

this is the post that got me curious , got me searching and found out what to do with 208's , just use 700r4 gears . Look at my reply in this thread , #10 . With my 18 tooth gear in case , my 32.5 inch tall tires , and my 3.73 gears , I come up with green 42 tooth gear needed http://coloradok5.com/forums/showthread.php?t=121705

 

[docgab]

this is the post that got me curious , got me searching and found out what to do with 208's , just use 700r4 gears . Look at my reply in this thread , #10 . With my 18 tooth gear in case , my 32.5 inch tall tires , and my 3.73 gears , I come up with green 42 tooth gear needed http://coloradok5.com/forums/showthread.php?t=121705

OK. This one knocked the cobwebs out of my head. I was looking for an easy way to tell what I needed as far as a DRIVEN gear goes. I guess I need to tear into my x-fer case and see what drive gear I have then? It all makes sense now. lol

 

[k5floyd]

tci's website helps alot, definately saves you from any mental stress doing the math yourself. thanks pauly

 

[BrianDamage]

OK. This one knocked the cobwebs out of my head. I was looking for an easy way to tell what I needed as far as a DRIVEN gear goes. I guess I need to tear into my x-fer case and see what drive gear I have then? It all makes sense now. lol

yep

you may be able to remove the cover from where the driven gear usually goes and see it from there