The Stovebolt Site Forums The Shop Area Engine Shop differencial

I am not sure how to ask this, but. How do I know if my differencial is the original or replaced by the PO? The reason to suspect a change is the hanger for the brake line tee is on the drivers side in the middle of the back facing back. I have changed out the brake cylinders, brake shoes, all the springs and clips, and the brake lines with parts listed for a 55 2nd. They all fit. I am confused about the hanger clip being on the rear drivers side.

When the wheels are turned the front spindle to the drive shaft spins approximately 2 turns. I don't have the engine or drive line in the truck.

When I get the engine back in the truck later this month I was just wondering what this will mean. Will this allow me to zip down the highway at todays speeds? I may want to go down to Georgetown and see the hill country in my Chevrolet. Or head out west and look for Aliens.

Any ideas? TIA

The best way to know the ratio is to count teeth, but estimating the ratio can be done as you did, rotate the tire(axle) while counting the number of turns of the drive shaft. The only question I have is in your counting. Most ratios in rears for trucks a at leat 3 to 1, many 4 to one. 2 to one is unheard of with very few exeptions, those being 1980's or newer car rear ends. The lower numerically the ratio, the faster the highway speeds, ie 3 to 1 allows you to drive faster than 4 to one, with corresponding loss of torque multiplication. I dont know the ratios offered in your years, but most in that era were 4.11 to 1, some also 4.56 to one. I think on a half ton it might be possible to see as low as 3.73(factory) and now some aftermarket companies offer a 3.55 to one.
I suggest a slow recount, make a mark so you dont get confused.

A standard non-locker differential is tough to get an accurate count on. Usually, the right side will turn, the left will sit still. Short of actually counting the gear teeth, the best method is to jack the right wheel only, leaving the left on the ground. Then count the revolutions of the wheel and double them. Sounds like you might have a 4.10 gear.

Try this:

"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 & 3/4 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." (quoted from West Coast Differentials)