The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post

Kiwi · 08-25-2010, 08:00 PM

I have a 1971 C10 (V-8, automatic, 2WD, long bed, 5-lug wheels). I recently installed a new TH700-R4 overdrive transmission and now the speedometer is reading too fast. I'm trying to determine what speedo drive gear I need to buy/install in the TH700-R4 ... which will be based on two factors:

- Rear tire size (I know this answer)
- Rear gear ratio (I don't know this answer)

1. What were the factory rear gear ratios available in 1971 for a C10?
2. Is the rearend ratio listed somewhere on a trim tag?
3. Did some/all of the C10 rearends come with a limited-slip differential? If so, does the limited-slip require using the liquid posi additive (such as with 1960's 10- and 12-bolt rearends) when changing the rear diff oil?
4. What type of rearend came in a 1971 C10 (I think it was a "Dana" ... but a Dana what??)?

08-25-2010, 08:00 PM	#1
Kiwi Registered User Join Date: Mar 2010 Location: Los Angeles, California Posts: 81	Rearend questions I have a 1971 C10 (V-8, automatic, 2WD, long bed, 5-lug wheels). I recently installed a new TH700-R4 overdrive transmission and now the speedometer is reading too fast. I'm trying to determine what speedo drive gear I need to buy/install in the TH700-R4 ... which will be based on two factors: - Rear tire size (I know this answer) - Rear gear ratio (I don't know this answer) 1. What were the factory rear gear ratios available in 1971 for a C10? 2. Is the rearend ratio listed somewhere on a trim tag? 3. Did some/all of the C10 rearends come with a limited-slip differential? If so, does the limited-slip require using the liquid posi additive (such as with 1960's 10- and 12-bolt rearends) when changing the rear diff oil? 4. What type of rearend came in a 1971 C10 (I think it was a "Dana" ... but a Dana what??)?