Gear Ratio Question

[M J]

I need to know the stock gear ratio on the 1991 W/T, 10 bolt rear-end, 2wd

 

I am hopefully putting lift on this weekend with 16" wheels (1" bigger than stock) and upgrading to 31.5" BFGoodrich Mud Terrians, from the stock ~27" tires. I need to know if its even worth changing gears (if the stock ones are 3.73 ill let them be, but if they're 3.10s i upgrade to 4.10s)

 

any insight is helpful!

[silvius]

I need to know the stock gear ratio on the 1991 W/T, 10 bolt rear-end, 2wd

 

I am hopefully putting lift on this weekend with 16" wheels (1" bigger than stock) and upgrading to 31.5" BFGoodrich Mud Terrians, from the stock ~27" tires. I need to know if its even worth changing gears (if the stock ones are 3.73 ill let them be, but if they're 3.10s i upgrade to 4.10s)

 

any insight is helpful!

 

 

I know it is a different year model and series, but the standard gear ratio on my dad's 88 silverado 350/1500 series was a rather high geared 2.73. I could see a work truck coming with a lower ratio standard, however, like a 3.42. In 1988 and 1989, the choices on half tons were 2.73, 3.08, 3.42, and 3.73, I believe. Is the RPO code sticker still in the glovebox? If so, the gear ratio is listed, but in 'code' form. This is assuming of course that no one changed out the rear end before you got it.

 

Good luck

[silveradoHO]

You'll have to find the RPO code to know for sure because there were different options for the gear ratios. The most likely possiblity is 3.42. Unless the truck was ordered by the costumer, almost all dealers got there trucks with this gearing, both 2 and 4wd.

[thecraft]

GU2 - 2.73 Ratio

GU4 - 3.08 Ratio

GU6 - 3.42 Ratio

GT4 - 3.73 Ratio

[jedcooper]

The RPO code is not always accurate.

After ordering a custom burned chip I learned the PO changed my rear end gears.

So, another burn is in order.

The most accurate method is to remove the rear end cover and count or read on the ring gear.

With that old of a truck, you're probably due for a gear oil change anyway.

 

Another method is to time a mile or so to get an accurate speed, then note your rpm at that speed.

Break out the tape mearsure for an accurate tire diameter reading and then plug the numbers into

this website:

 

http://www.bncoffroad.com/tire_gear_cal.html

 

By trying different gear ratios it will tell you what you have.

Oh yeah, you'll need your gear ratio for your tranny.

If you don't know, a quick google search will turn up plenty of info.