Gear Ratio?

[shakes82]

How do I find out what gear ratio came in my truck?

[chevyblazer]

do you wanna now the original gear that shuod have its kind of hard unless it haves the original drive train check out glove box if its the ori.

[burb71]

Drain it, remove the rear cover, look on the ring gear find the stamped code,
one set of numbers are a date code, the others or the numbers of teeth on the ring gear and the number on the pinion, divide the two and you have it.

[cdowns]

Originally Posted by burb71

Drain it, remove the rear cover, look on the ring gear find the stamped code,
one set of numbers are a date code, the others or the numbers of teeth on the ring gear and the number on the pinion, divide the two and you have it.

thats the best way . while you're at it take a spray can of brake cleaner clean it up refill with synthetic gear oil(2quarts) and you're good to go

it will be an hour well spent

[raycow]

There's a best way, and there's an almost as good way without having to get greasy.

Put matching marks on the pinion yoke and differential housing. Jack one rear wheel off the ground, put the transmission in neutral, and the parking brake off. Turn the wheel exactly TWO revolutions and count how many times the driveshaft turns, estimating any fractional turn as closely as possible. That number is your axle ratio.

If the wheel is difficult or impossible to turn, you may have posi. In that case, jack both rear wheels off the ground and turn either of them only ONE revolution. Count the driveshaft turns the same way as for an open rear.

Ray

[Longhorn Man]

the gear oil is probably 20 to 40 years old, and only working at 50 to 75% what it was when filled. So a drain and fill is a good idea for any reason.
However, the initial question was asking what was there originally, not what is there now.
What year, what size truck (10, 20, 30) what engine and what tranny was original... all this assuming nothing was listed on the SPID for optonal gears

[chevyblazer]

yeah y like the last one but y always have problem that way sometimes the tire spins not equilie

[shakes82]

Thanks for the help.

[Quackaddict]

I prefer the drain and look method if the truck is new to you that way you can get some new fluid in there anyway and find out.