Changing rear axle ratios 4:11 to 3:73

[bubbaNcolo]

I've got a 71 3/4 burb with 4:11s, the rear axle cover is a 14 bolt cover. I don't know what it really is Dana or ??? Drum is 11" X 2 3/4" at least.
Can anyone tell me how to determine what type of rear axle I've got?
Then the next thing would be can I put 3:73 ratio in?

[1969 GMC]

with 14 cover bolts it means you have a 14 bolt rear axle, which wasnt stock in that truck. they are pretty easy to get parts for.

[bubbaNcolo]

I think there are a few things that aren't stock on this burb. Any clues to what the rear end is from or what it is called other than a 14 bolt rear axle?

[jku72]

I just did some research on this a couple days ago on this board.
On the 14 bolt, there is a 3.73 available, as well as 3.42, and even an aftermarket 3.21 ratio, for those whose drive the highway.
There are 2 versions of the 14 bolt, a 9.5 inch ring gear, and a 10.5. I think, the 9.5 is a semi floating rear, and the 10.5 is a full floater.

[bubbaNcolo]

I believe a full floater is where you have 6 bolts holding in your axles to the drum. Mine the drum just slide off no bolts no bearings. So based on that maybe a 9.5" rear end. When they say 9.5" where or what dist or diamention or they refering to?

[jku72]

Thats ring gear diameter. And it sounds like you have the 9.5 semi floating rear.
Go to a site called "Randy's ring and pinion", and check out the charts to see what gears a re available.

[1972C10]

They made 8 lug semi floaters Basically if you can pull the drum off without removing the axles and two nuts its a semi 9.5 "

But if you have 8 bolts in a small cirlce and a knub sticking out the center its a full floater. 10.5"