Help on differential please...

[69_C10]

Hey guys,
I have a question for my friends out here. I have a 12-bolt in my truck and, it's also a posi. What I don't know is what gear ratio it is. Since there really isn't marking to tell me, what is the best way to get the gear ratio?

Thanks everyone,
Mark Ingle - Asheville, NC

[C10Slim]

You can remove the differential cover and count the number of teeth on the gears, but that can get messy.

Poor mans version: You can also jack up the rear put it in neutral. Use chalk to mark the tires and ground so you have starting point also mark the drive shaft to the frame or rear end. While rotating the wheels 1 full turn count how many times the drive shaft rotates. So 3 full turns and a almost a quarter would equal like 3.23 gear. It's not super accurate but would put you in the ball park.

[69_C10]

Originally Posted by C10Slim

You can remove the differential cover and count the number of teeth on the gears, but that can get messy.

Poor mans version: You can also jack up the rear put it in neutral. Use chalk to mark the tires and ground so you have starting point also mark the drive shaft to the frame or rear end. While rotating the wheels 1 full turn count how many times the drive shaft rotates. So 3 full turns and a almost a quarter would equal like 3.23 gear. It's not super accurate but would put you in the ball park.

Hey, poor mans version is the only way I can roll. Thanks for the reply. I'll give it a try.

[LONGHAIR]

The numbers (tooth count) are stamped on the edge of the ring gear. Pull the cover off, spin the gear around (while wiping the lube out of the way) and you will find the numbers. It will be two 2-digit numbers seperated by a dash. 41-10, 41-11, 41-12, 40-13, etc. Divide the smaller number into the bigger.
41-10= 4.10
41-11=3.73
41-12=3.42
40-13=3.07