1990 Suburban 1500 - Gear Ratio

[90Suburban]

Hey Everyone,

I have a 1990 Suburban 1500. What was the common gear ratio found for those criteria? Thank you!

Oh and it has the stock 10 bolts front and rear.

 

[jeff in co]

3.42 or 3.73

 

[90Suburban]

3.42 or 3.73

Is there a way to tell for sure?

 

[readymix]

If the truck is all original you could look for the RPO code sticker in the glovebox. I have a few hundred pages of RPO codes here.
The best way would be to pull the diff covers and count the teeth. Clean it all up and change the gear oil at the same time.

 

[Blue85]

All you have to do is search....

If you don't want to pop the diff cover, you can turn the driveshaft and see how many revolutions per revolution of the tires.

And if you do want to pop the cover to change oil and inspect, the ring gear always has the tooth counts stamped on the edge (sometimes people say here that the gear ratio is stamped on the gears, which is not true. You calculate the ratio by diving the ring gear count by the pinion gear count)