PG speedo drive gear & driven gear w/30.5 tires

[Irishbleueyes]

3.73 rearend, does anyone know what color gears for 30.5 tires? Or just a driven gear change? Thanks in advance

[1Ratty64]

If you know your drive gear tooth count you can use this formula to choose the best driven gear. According to NTW a 30.5" tire does 684 revs/mile

(# Drive Teeth x Axle Ratio x Tire Rev. per Mile) / 1001 = driven gear tooth count

[Irishbleueyes]

Originally Posted by 1Ratty64

If you know your drive gear tooth count you can use this formula to choose the best driven gear. According to NTW a 30.5" tire does 684 revs/mile

(# Drive Teeth x Axle Ratio x Tire Rev. per Mile) / 1001 = driven gear tooth count

Cool, I was hoping someone knew which drive gear came with PG and 3.73 in a c10

[1Ratty64]

tire size will throw it off pretty considerably.....take for instance using your combination and if you had a 8T drive gear you would be best with a 20T (blue) driven which originally came in 3.08 axle ratio. There were several different combinations of drive/driven gear sets to account for different tire size/gear ratio combinations

[Irishbleueyes]

Originally Posted by 1Ratty64

tire size will throw it off pretty considerably.....take for instance using your combination and if you had a 8T drive gear you would be best with a 20T (blue) driven which originally came in 3.08 axle ratio. There were several different combinations of drive/driven gear sets to account for different tire size/gear ratio combinations

Oh it did, I bolted the rears on today and went down the street and the speedo was way slow. I see the gears on ebay are cheap, I'll get a variety pack and check it out. It was sluggish off the line so it may be time to put in a th350 that has the lower 1st gear.

[VictoriaHardware]

Originally Posted by Irishbleueyes

Cool, I was hoping someone knew which drive gear came with PG and 3.73 in a c10

Original drive gear was black (8 tooth, p/n 6261783) and driven was probably black (23 tooth, p/n 3987923). It varied with optional tire sizes.

Speedometer heads are calibrated to read 60 mi/hr at 1,000 speedometer cable rev/min.

[Irishbleueyes]

Originally Posted by VictoriaHardware

Original drive gear was black (8 tooth, p/n 6261783) and driven was probably black (23 tooth, p/n 3987923). It varied with optional tire sizes.

Speedometer heads are calibrated to read 60 mi/hr at 1,000 speedometer cable rev/min.

Oh cool, thank you. It was exactly right on with the p235 75r 15 so I was bummed when it was way off. I will pull the cable and bullet and see if thats whats in there. Is there a point where the driven gear wont match up with the drive gear? Like a range low to high with each drive gear or does any driven gear work with any drive gear? Just wondering..

[1Ratty64]

You should be good, there is a different housing size when you get into the large drive and driven gears but you "should" have a small drive gear and to the best of my knowledge all the driven gears that fit that housing will work with whatever drive gear you have in there....which is more than likely the small 8 tooth.

Just looked it up and 18-23 tooth driven gears fit the powerglide housing.