The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - 1979 Chevrolet C70 Ring and Pinion Upgrade

Airdirect · 02-15-2017, 01:30 PM

I considered replacing the whole third member, however my truck only had 45,000 original miles and I wanted to keep the low mileage components.

One of the big differences is the 4-53T Detroit Diesel only turns 2,500 RPM. To achieve 70 MPH you need a much higher rear end ratio. With the 4.56 gears I now govern out at 67 MPH. If I had 4.11 I could run 70 MPH and not be against the governor. If I were selecting a new ring and pinion set I would try the 4.11. Regarding the tires, I am planning on putting new tires on the truck, still trying to decide between original 9.00 X 20 or 11.00R X 22.5. To go with the 22.5 I would need new tubeless rims.

02-15-2017, 01:30 PM	#13
Airdirect Registered User Join Date: Oct 2016 Location: Powderly Texas Posts: 301	Re: 1979 Chevrolet C70 Ring and Pinion Upgrade I considered replacing the whole third member, however my truck only had 45,000 original miles and I wanted to keep the low mileage components. One of the big differences is the 4-53T Detroit Diesel only turns 2,500 RPM. To achieve 70 MPH you need a much higher rear end ratio. With the 4.56 gears I now govern out at 67 MPH. If I had 4.11 I could run 70 MPH and not be against the governor. If I were selecting a new ring and pinion set I would try the 4.11. Regarding the tires, I am planning on putting new tires on the truck, still trying to decide between original 9.00 X 20 or 11.00R X 22.5. To go with the 22.5 I would need new tubeless rims.