Rear end ratio question. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

krue · 09-01-2007, 01:27 PM

I pulled a rear from a late 70's 1/2 ton. When I pulled the cover I found 10:34 stamped on the ring gear and counted the teeth and got 34 on the ring gear and 10 on the pinion. That calculates to a 3.40 ratio, but I always thought it was a 3.42, so what gives?

454HO · 09-01-2007, 06:24 PM

Quote:

Originally Posted by krue

I pulled a rear from a late 70's 1/2 ton. When I pulled the cover I found 10:34 stamped on the ring gear and counted the teeth and got 34 on the ring gear and 10 on the pinion. That calculates to a 3.40 ratio, but I always thought it was a 3.42, so what gives?

That's exactly what my '77 12-bolt has, 3.40 gears stock from the factory. It's even listed that way on the RPO sheet in the glove box.

krue · 09-01-2007, 07:17 PM

I couldn't find a 3.40 in any of the catalogs I looked at, so I was wondering.

gchemist · 09-01-2007, 08:40 PM

3.42 are common to the 88+ trucks because of the V-6. I would like to find a 12 both with 3.40 gears for my truck.

Texasdeere · 09-02-2007, 05:40 PM

Quote:

Originally Posted by 454HO

That's exactly what my '77 12-bolt has, 3.40 gears stock from the factory. It's even listed that way on the RPO sheet in the glove box.

Same here on my 78 BB C10

09-01-2007, 01:27 PM	#1
krue Designated A-hole! Join Date: Mar 2003 Location: South Mississippi Posts: 36,448	Rear end ratio question. I pulled a rear from a late 70's 1/2 ton. When I pulled the cover I found 10:34 stamped on the ring gear and counted the teeth and got 34 on the ring gear and 10 on the pinion. That calculates to a 3.40 ratio, but I always thought it was a 3.42, so what gives? __________________ "If it ain't broke, fix it 'til it is!" Being stupid ain't illegal. We're Still Debt Free Except for the House!!! www.daveramsey.com 70 GMC SWB Stepside project "Green Booger" soon to be 6.0l/4l80e 93 S-10 "Poppaw's Truck"

09-01-2007, 07:17 PM	#3
krue Designated A-hole! Join Date: Mar 2003 Location: South Mississippi Posts: 36,448	Re: Rear end ratio question. I couldn't find a 3.40 in any of the catalogs I looked at, so I was wondering. __________________ "If it ain't broke, fix it 'til it is!" Being stupid ain't illegal. We're Still Debt Free Except for the House!!! www.daveramsey.com 70 GMC SWB Stepside project "Green Booger" soon to be 6.0l/4l80e 93 S-10 "Poppaw's Truck"

09-01-2007, 08:40 PM	#4
gchemist BAD BOW-Silverado XST Join Date: May 2000 Location: Senior Member from Austin, TX Posts: 6,431	Re: Rear end ratio question. 3.42 are common to the 88+ trucks because of the V-6. I would like to find a 12 both with 3.40 gears for my truck. __________________ Gerardo a.k.a. Mad Chemist Silverado XST videos



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