Used the tire/driveshaft gear ratio check! - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Sooner1970_K10 · 02-14-2005, 07:24 PM

Ok, we finaly had a warm day and I went outside and jacked a rear tire up in the air and counted the driveshaft turns in comparison to the tire turns. The driveshaft was easy, it had a small balance weight on it. The tire had a small white rock in its tread that was exactly TDC when the driveshaft balance weight was TDC on the driveshaft. So here is what I did. I have never done this before and just want to check and make sure I did it right!

I turned the rear tire 2 full turns and the driveshaft went around 3 1/6-1/4 times. I did this twice and came up with the same numbers.

If I am to figure this right, I should have a 3.08 rearend gear ratio?

The truck is a 1970 k10. Does this all sound correct?

Thanks for those who posted how to accomplish this.

**JIMs70GMC** · 02-14-2005, 09:38 PM

That is correct.

Nick's683/4 · 02-15-2005, 02:53 AM

my 1970 k10 has 3.07 in it too...

02-14-2005, 07:24 PM	#1
Sooner1970_K10 1970 K10, 350, 4spd! Join Date: Jun 2004 Location: Shawnee, Ok Posts: 128	Used the tire/driveshaft gear ratio check! Ok, we finaly had a warm day and I went outside and jacked a rear tire up in the air and counted the driveshaft turns in comparison to the tire turns. The driveshaft was easy, it had a small balance weight on it. The tire had a small white rock in its tread that was exactly TDC when the driveshaft balance weight was TDC on the driveshaft. So here is what I did. I have never done this before and just want to check and make sure I did it right! I turned the rear tire 2 full turns and the driveshaft went around 3 1/6-1/4 times. I did this twice and came up with the same numbers. If I am to figure this right, I should have a 3.08 rearend gear ratio? The truck is a 1970 k10. Does this all sound correct? Thanks for those who posted how to accomplish this.

02-14-2005, 09:38 PM	#2
JIMs70GMC user # 2756 Join Date: Jun 2001 Location: Chesapeake, Virginia Posts: 4,612	That is correct. __________________ 1970 K25, 8' stepside bed 350/465/205 44 up front, 60 in the rear 4.10s rolling on 33" Dunlop MTs 1986 K5, 350/465/208 Dana 60/14 bolt from a cucv 36" Super Swampers TSL/SX 1983 K20 w/ CUCV axles, 350/700R4/208 sitting on 37" Goodyears 1986 M1031 6.2 diesel, TH400/NP205 locker in the rear and a LS in the front, all stock for now..... 1986 K30, 350/400/205 dana 60 and 14 bolt. I kept the drivetrain. Body/bad and chassis are gone. 1981 K30, 350/465/205 dana 60 and dually 14 bolt. Has a G80, and a flat bed. Going to replace the flat bed. 1985 K20, 350/400/208 10 bolt and SF 14 bolt. I wonder where I can find some 1 tons. Hmmmmm

02-15-2005, 02:53 AM	#3
Nick's683/4 Registered User Join Date: Apr 2004 Location: Oakley CA Posts: 165	my 1970 k10 has 3.07 in it too... __________________ 70 1 ton with a 454 and a 4 speed and a np205



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