gear ratio?

[outlaw]

I was wondering if someone could tell me what my gear ratio is for my 1970 chevy truck with a 307 1/2 ton long wheel base 3 spd on the column, rear coil springs

[crazy longhorn]

3.07 & 3.73 were the most common gears in the 1/2 ton trucks(2 wd). most of the stick shift trucks that I have seen were a 3.73 gear. There was a 4.11 ratio offered, but only with 3 spd/OD trans(pretty rare). Im not positive, but think there was a 3.36 ratio in the mix also.....crazyL

[dmnall]

From what I have read on the whole gear ration set up, is look at the Glove Box Sticker, if it says something like 4.11 or 3.07's then that is the gear ratio in your truck, Otherwise it is 3.73...

Charlie

[outlaw]

Thanks will look when I get home

[outlaw]

when I got home I looked in the glove box and it did not say anything about gear ratio's so does that mean that it is a 3.73 or what does that mean,thanks Danny

[crazy longhorn]

My bet would be a 3.73 on a stick shift 1/2 ton, the auto trucks generally had a taller rear diff. You can pop the cover & check, or if you are running a tach, figure that 2800-3000 should put you close to 65 mph with a 3.73 gear. crazyL

[CJM72CHEVY]

Jack up the rear end, mark the driveshaft and one tire with white marker or something, and see how many drive shaft revolutions it takes to turn the wheel one turn. Or, it might (probably will) be easier to use the tire to turn the driveshaft. Either way, the results will be the same. If it's around 3, you probably have 3.08s. If it takes more than 3.5 but less than 4 full turns, you probably have 3.73s. The other, more time consuming method is to pull the rear cover, count gear teeth, and divide the ring gear count by the pinion gear tooth count. My '72 C-20 doesn't have the gear ratio listed in the glovebox, either. I pulled the cover to change lube, and found it to have 4.58s (32 tooth ring gear and 7 tooth pinion). The 7-32 was also stamped in the end of the pinion gear in plain sight, but that's on an Eaton axle, and you likely have a 12-bolt.

[crazy longhorn]

if you opt to pull the cover, the 12 bolt will have the 2 numbers you need stamped on the outer edge of the ring gear. When checking turns of the axle/d shaft, remember that on an open diff, the spider gears will "goof " with your count when figuring ratio. the spiders step up the axle speed when 1 wheel is spinning 2 to 1. thats why a "1 wheel peel" makes so much smoke. crazyL

3.07 was standard at the time, but you had the option to go to a 3.73 if you wanted it. So unless it says on the glovebox door that it was changed out/or someoneless changed it then its a 3.07