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| | | | Joined: Jan 2007 Posts: 446 Shop Shark | | Shop Shark Joined: Jan 2007 Posts: 446 | Okay, something's weird here. Some of you may remember that I'm preparing to swap rear differentials in my 1966 C60 to a 2 speed. Come to find out the 2 speed is out of a GMC 2 ton and it's a T170 according to the numbers. (GM 3873551).
So, today I went out and made a chalk mark on the hub and another chalk mark on the carrier where the drive line hooks up. I turned the hub one full revolution and counted 3.25 turns at the drive line. REALLY!!!! I'm assuming the differential is in high gear but 3.25 gears in a 2 ton rear differential. I must have done something wrong. I have read that these T170's normally run 6.50's.
Any ideas? Any help would be appreciated, thanks! | | | | | Joined: Feb 2004 Posts: 29,749 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,749 | If one wheel is still on the ground, the spider gears will double the gear ratio. The best way to get an accurate ratio check is to count the teeth on the ring gear, and divide that number by the pinion teeth.
Example: Ring gear-37 teeth
Pinion gear-10 teeth
Gear ratio-37 divided by 10=3.70:1
Jerry
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| | | | | Joined: Jan 2007 Posts: 446 Shop Shark | | Shop Shark Joined: Jan 2007 Posts: 446 | Hello Jerry. The rear differential doesn't have tires on it and it's sitting on saw horses, no restrictions on the hubs. The drive wheel should be the passenger side, right? | | | | | Joined: Sep 2006 Posts: 1,276 Shop Shark | | Shop Shark Joined: Sep 2006 Posts: 1,276 | What Jerry said is true in order to get an accurate reading doing it how you did it you must turn the hubs together. There is no drive wheel or non drive wheel the reason the passenger side tire spins on an open diff car is the rotation of the drive line tries to turn the entire axle assembly the same direction lifting the passenger side tire so it loses traction. If you were to do a burnout in reverse the drivers side would spin.
Last edited by HevyHauler; 10/07/2013 5:06 AM.
| | | | | Joined: Jan 2008 Posts: 4,961 'Bolter | | 'Bolter Joined: Jan 2008 Posts: 4,961 | Sounds like you have the common 6.50 ratio. | | | | | Joined: Mar 2004 Posts: 6,214 'Bolter | | 'Bolter Joined: Mar 2004 Posts: 6,214 | Check the end of the Pinion Shaft and see if the gear teeth counts are stamped there. Mike B  | | | | | Joined: Dec 2003 Posts: 2,733 Shop Shark | | Shop Shark Joined: Dec 2003 Posts: 2,733 | The most common std ratio on a 17K rear was 6:50/7:17. Probably what you have. I used to operate these and most would run 65 MPH in the high side and against the governor. They were commonly used behind 350 and 366 V8's, possibly with 427's but most of those chassis had larger/heavier rears. | | | | | Joined: Jan 2007 Posts: 446 Shop Shark | | Shop Shark Joined: Jan 2007 Posts: 446 | Thanks Mike and Dave. Just the good news I was looking for I was hopeful it would be 6:50 and that should take care of my problem! | | |
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