Going to look at this on Saturday

[mbs17]

Hi all - new member and love the site quite a bit of info to digest. I am going to look at this 66 c10 long bed step on Saturday. about a 3 hr drive from me. If i get it i want to make it a daily driver and keep the 6 and add a t5 to it- my question to you guys is this-after much searching and reading I just can't find a thread that will help me determine what the rear gear ratio is- what should i look for on the truck to try and figure it out?
thanks in advance for your help.
Michael

btw: 6 cyl 3 on the tree needs"a heater core" we will see

[LILRED66]

Welcome to the forums from Kansas City, KS and thanks for sharing. It appears the truck you are prospecting is a '65 according to the body badges, but a '65 is, virtually identical, to the '64 and '66.

Regarding the rear differential ratio, the only sure-fire way to determine is to remove the pumpkin cover, count the teeth on the ring gear, count the teeth on the pinion gear and divide the large number by the small number...the result is the rear-end gear ratio. Standard equipment in the '64-'66 Chevy 2wd, 1/2 ton trucks was 3.73:1, but no telling what has been done over the years.

[lakeroadster]

To check rear end ratio jack up one tire if you have an open diff, or both tires if you have a working posi or locking differential. Rotate the tire one full revolution for posis and lockers and 2 full revolutions for open diffs. Carefully count the number of full revolutions the driveshaft makes. This is your gear ratio. In other words, if the drive shaft turns 3 ¾ turns, you probably have a 3.73 gear ratio. Turning the tire for twice the number of full revolutions and dividing the drive shaft revolutions by two will give you a more accurate reading.

[Alan's Classic]

to the funny farm Good luck with the truck. I saw it also, let us know how it turns out.

[mckeagplm]

You might be able to find a tag on the pumpkin indicating what the ratio is.

[LILRED66]

Jacking/rotating wheels and going by the tag are not sure-fire ways to determine the actual rear-end gear ratio. Ring and pinion gears get changed over the years and the original tag may remain, so you may not know, for sure. Pulling the rear cover is a great reason to change, clean and service the rear differential, therefore you will know exactly what your ratio is.

[lakeroadster]

Originally Posted by LILRED66

Jacking/rotating wheels and going by the tag are not sure-fire ways to determine the actual rear-end gear ratio. Ring and pinion gears get changed over the years and the original tag may remain, so you may not know, for sure. Pulling the rear cover is a great reason to change, clean and service the rear differential, therefore you will know exactly what your ratio is.

Tony, keep in mind the original post was a guy going to look at a truck, 3 hours away (see original post). Most owners would have a problem with the prospective buyer pulling the rear cover, unless said prospect buyer cleans the cover and case and then puts on new RTV sealant and fills the pumpkin back up with new gear lube for free. If that's the case, anybody want to come over and look at my truck? (just kidding)

I agree that ring and pinion gears get changed over the years and the original tag may remain, so you may not know, for sure.

But rotating the tire and counting the drive shaft revolutions is a sure fire way to determine the rear gear ratio. It's a mechanical gear set, if you follow the directions there is no way it can't work. And for a prospective buyer, it's quick and accurate.

But you are right that the quick method won't tell you anything about the integrity or condition of the actual gears.

[mbs17]

just an update- truck sold so i looked at another 66 nice looking truck until you got up close- more rust than i am comfortable with- so the search continues- here is a pic of the one i looked at.