Rear Axle Question

[Goldengophersax56]

Idk if I'm blind or if the forum doesn't exist, but I have a question about a 76 2wd Blazer rear end. Would anyone know what the gear ratio for those typically was? It's a 12 bolt. I was looking in LMC's catalog but there was a handful of options.

Worst case scenario, I pop the cover, but I'd prefer that I didn't have to if at all possible.

Thanks!

[Titomars]

The most common gear ratio I have seen for the 73 to 78 C-series with the 12 bolt axle was 3:42's but it really depends on engine, trans, and option levels. Plus if it was special ordered it could be anything.
You don't really need to open it up. Assuming nobody went in it and changed the ring and pinion there is a axle code you can get off the housing. It is on the right axle tube facing towards the front of the vehicle and generally a few inches out from the cast center section. The code will have 2 letters and I think 5 numbers. The 2 letters will tell you the gear ratio and if it was posi or not, the numbers are the built date. There are charts all over the internet for determining the letter code.

[68post]

You can also place a floor jack under the center section and lift both tires, turn the tire one full revolution and count how many turns the driveshaft makes.

Just under 3 1/2 turns + 3.42 (barely under ), just over 3 1/2 turns = 3.55 ( barely over ), right at 3 turns = 3.08, 3 3/4 turns = 3.73, ...you get the msg.

Hope this helps.

[Goldengophersax56]

Thanks guys! I'll check it out after work today.

[Keith Seymore]

Powertrain charts and link to GM Heritage Center generic info packet attached.

3.73 was considered standard; 3.07 or 4.11 were also available optionally.

K

https://www.gmheritagecenter.com/doc..._Full-Size.pdf