Chevy rear end axle ratio
Question:
I have a question i hope someone could help me with. I have a ‘79 Chevy truck with 350 4 barrell automatic, C-10 (Big 10). I am wondering what the rear end axle ratio is. I am getting ready to rebuild a new motor for it and am wondering about the cam selection and torque vs. hp. i have copied some numbers down that i saw on the rear end casing that i hope someone could help me decipher: 3896839 with an "N" below it. and c10 (for the truck model i assume) and GM81 I know the original owner and am certain the truck is all original. According to one book, the 305 was "standard" for the Big 10 and the standard ratio was 3.40. But i have the 350 option and wonder if it is different. I know the 3.07, 3.40, 3.73 and 4.10 are all possibilities. andy help would be very appreciated. thanks Andy www.delbridge.net
Response:
The Big 10, and the GMC Heavy Half, were just that – heavy half series, which typically gave a bit more GVW. I had the same truck in the GMC, and mine was a 3.07:1. There should be three letters stamped into the axle tube on the passenger side, just off of the ring and pinion. Get a wire brush out and hope that the rocks haven’t beat it smooth. Then you take this into the GM PArts Dept and have them look it up in their parts catalog. That’s how I found out what mine was… jed
– Hide quoted text — Show quoted text -> I have a question i hope someone could help me with. I have a ‘79 Chevy truck > with 350 4 barrell automatic, C-10 (Big 10). I am wondering what the rear end > axle ratio is. I am getting ready to rebuild a new motor for it and am > wondering about the cam selection and torque vs. hp. i have copied some > numbers down that i saw on the rear end casing that i hope someone could help > me decipher: > 3896839 with an "N" below it. > and > c10 (for the truck model i assume) > and > GM81 > I know the original owner and am certain the truck is all original. According > to one book, the 305 was "standard" for the Big 10 and the standard ratio was > 3.40. But i have the 350 option and wonder if it is different. I know the > 3.07, 3.40, 3.73 and 4.10 are all possibilities. > andy help would be very appreciated. > thanks > Andy > www.delbridge.net
Response:
Your axle code is stamped on top of the right rear axle tube. Additionally, it can be compared to the RPO listed on the Service Parts Data decal. The axle codes start with the letter "G". For instance a 3.42 would be "GU6".
– Hide quoted text — Show quoted text -> I have a question i hope someone could help me with. I have a ‘79 Chevy truck > with 350 4 barrell automatic, C-10 (Big 10). I am wondering what the rear end > axle ratio is. I am getting ready to rebuild a new motor for it and am > wondering about the cam selection and torque vs. hp. i have copied some > numbers down that i saw on the rear end casing that i hope someone could help > me decipher: > 3896839 with an "N" below it. > and > c10 (for the truck model i assume) > and > GM81 > I know the original owner and am certain the truck is all original. According > to one book, the 305 was "standard" for the Big 10 and the standard ratio was > 3.40. But i have the 350 option and wonder if it is different. I know the > 3.07, 3.40, 3.73 and 4.10 are all possibilities. > andy help would be very appreciated. > thanks > Andy > www.delbridge.net
