Differiential question (POSI) - The 1947 - Present Chevrolet & GMC Truck Message Board Network

jay_shy · 10-13-2006, 07:24 PM

There is an add in the local trader paper for a 72 gmc 12 bolt posi truck rear. Whats a good/fair price to ask. Also how can I tell if it is compatible with our trucks. I plan on using it with 3.73 gears. How do I tell which series the carrier is.

Is there anything else I need to know when I go and look at it?

Thanks in advance

Jason

Aarons72s · 10-13-2006, 07:49 PM

More than likely the gmc will have leafs so I think it will work but then again I havent been luck enough to deal with 67-72 4x4's yet. If it will work for you 100 for a posi is real good if it is in working condition. To tell the gear ratio you need to drop the cover and count the teeth on the ring and pinion. Then ring teeth/ pinion teeth= gear ratio. Look at the oil and look for metalic particles, ie metal shavings, look for evidence that water has gotten inside it, ie rust or chocolate milk, inspect the teeth to make sure they are in fairly good shape, ie no missing teeth. Good luck.
Aaron

10-13-2006, 07:24 PM	#1
jay_shy SWB 4X4 CLUB Join Date: Feb 2005 Location: PA Posts: 1,088	Differiential question (POSI) There is an add in the local trader paper for a 72 gmc 12 bolt posi truck rear. Whats a good/fair price to ask. Also how can I tell if it is compatible with our trucks. I plan on using it with 3.73 gears. How do I tell which series the carrier is. Is there anything else I need to know when I go and look at it? Thanks in advance Jason Last edited by jay_shy; 10-13-2006 at 07:50 PM.

10-13-2006, 07:49 PM	#2
Aarons72s Registered User Join Date: Apr 2006 Location: oklahoma Posts: 10,670	Re: Differiential question (POSI) More than likely the gmc will have leafs so I think it will work but then again I havent been luck enough to deal with 67-72 4x4's yet. If it will work for you 100 for a posi is real good if it is in working condition. To tell the gear ratio you need to drop the cover and count the teeth on the ring and pinion. Then ring teeth/ pinion teeth= gear ratio. Look at the oil and look for metalic particles, ie metal shavings, look for evidence that water has gotten inside it, ie rust or chocolate milk, inspect the teeth to make sure they are in fairly good shape, ie no missing teeth. Good luck. Aaron



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