1971 GMC C2500 rear end questions

[Baime]

Originally Posted by Ironangel

Baime, thats a Dana 60 in your pic, KEEP IT! Dont let anyone who dont know what it is touch it! There is no such thing as a "T400R4"...Need to determine what gearing is in it now by pulling the cover and getting the numbers off the ring gear. You will also be able to determine what carrier you have at the same time. The Dana 60 only goes as high as 3:55 and as low as 7:17 with the carrier break at 4:10/4:56. Nows the time to ask yourself what exactly are your plans for your 3/4 ton Jimmy? Are you pulling heavy trailers and hauling heavy loads? Do you have a $3K to invest in a gear set, a posi or locker, and a questionable 700r4? Not trying to rain on your parade but transforming a 71 3/4 ton GMC into gas friendly daily driver is an expensive endeavor. The least expensive way out is a new 3:55 gear set and taller 16" tires and wheels...My daily driver has 3:73 gears turning 31" 275/70R-16's with a built 350 Turbo to pull a tandem trailer with another 4000lb truck on it. If mileage is paramount, then you cant afford to drive these old trucks..."Just Sayin"

IronAngel,
I agree, I have to make this decision based on how I want to use my truck. I just really like my truck, and started to think that changing the rear end gearing and adding positraction would be a nice update/improvement. It isn't a necessary change. It obviously is geared more for pulling and hauling, than going 75mph on the highway.

How do you like your setup with the 350 Turbo, and the 3:73 gears?
I believe I have the 350 Turbo with 4:11 gears. It could be 4:10. Any idea what rpms you engine is running at going 70mph with the 3:73 gears?


I mostly make highway trips up to my cabin a hundred miles away, hauling what I need in the back, and I pull my boat a few hundred miles a year. I also enjoy just driving it around town in the non-winter months.

Thanks,
JP