Rear Differential

Also if anyone has one for sale and let me know.

Rear Differentail ratio for a 79 Blazer 4x4 W/ 350 How do you find out what the ratio is for both Differentials? I need to replace the one on the rear of my blazer 4x4

Code Written in the Glovebox Call a gm dealer and with that Code they can tell you.. There use to put a TAG on the Third memmber also

R. J Younger wrote:

if you can read the RPO code in the glove box thats a place to start, also I believe there are some numbers on the rear end housing that may help, you may have to resort to counting gear teeth.

i found the number GM74 on the differentail casing.

Thats a CASTING NUMBER

Well, Someone here helped me with number. its g80. Now. Do I need to call a dealer to get ratio on that or what?

Sry for all the questions.

But I found this info on net. RPO FY LY DIVISIONAL RPO DESCRIPTION G80 76 88 AXLE,RR LOCKING TYPE

What to look for now?

YES

Thanks everyone for the help.

G80 just pertains to the axle being a locking rear axle, nothing about the ratio. There's another G code in the glovebox, that's the factory-installed ratio...

it is HE4.