64 c10 rear end question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

shuvl · 04-28-2011, 10:15 AM

Found casting marks N 3838227 GM5. Cannot locate "N" on any of the tables found on internet. When I spin the tire the drive shaft spins just a hair over two times. My first question is what gearing do I have? It's a straight 6, 3 speed on the column and I have 17 inch wheels. At 65mph I'm at 3200 rpm. I'd like to increase my highway speeds and decrease my rpm's. Which gearing should I go with?
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**PGSigns** · 04-28-2011, 11:50 AM

Going by the rpm I would say 3.73
Jimmy

**MikeN** · 04-28-2011, 02:20 PM

Almost 100% of 64-66 with 6-cyl and 3-sp manual are 3.73's.

oldtrux · 04-28-2011, 06:36 PM

i would leave the 373's and put in a 5 speed od trans imho!

shuvl · 04-28-2011, 07:31 PM

Well I took the cover off and found 4:11 gears and gear lube that didn't look like it had ever been changed. So if I want to keep the three speed what would y'all suggest I put in for gears?
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fleetsidelarry · 04-28-2011, 07:59 PM

cheapest way would be to find a 3.07. better way is to do the OD. Best way is to do the 3.73 (a common gear in our trucks) AND the OD.

if I'm doing the math correctly:

if you are 3200@65 now, a .7 OD gives 2240@65. the 3.07 is like a .75 OD, giving almost 2400@65.

the 3.73+OD would yield ≈ 2000@65

my 3.07/700r4 (.7 OD) runs about 2000@75, more or less

collins10672 · 04-28-2011, 11:23 PM

the 3:07 was the highest gear available in the 64-66 trucks.kind of hard to find though.

**Captainfab** · 04-29-2011, 02:22 AM

The 3.42 gears are a good comprimise between the 3.73's and 3.07's

shuvl · 04-29-2011, 11:52 AM

Thanks for all the advice. That's why I like this group, its a plethora of knowledge and no BS attitudes.
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jimmydean · 04-29-2011, 02:12 PM

Quote:

Originally Posted by collins10672

the 3:07 was the highest gear available in the 64-66 trucks.kind of hard to find though.

You could also go with a 67-69, I seem to find quite a few 3.07's around here.

**Clyde65** · 04-29-2011, 02:35 PM

If you go OD trans, pick the 3.73's if you can, if you steel a deal, 3.42's will also work with an OD trans.

I have heard that the 3.08's are better for 3speed tranny's, but I have no real experience with them other than my truck now has the 3.08's and a 4 speed, I would enjoy it more if there were 3.73's or at least 3.42's back there. the only reason I am staying with the 3.08's is because I just rebuilt the rear about 3 months b4 I did my LS swap and OD trans.

04-28-2011, 10:15 AM	#1
shuvl Registered User Join Date: Apr 2011 Location: naples, fl Posts: 42	64 c10 rear end question Found casting marks N 3838227 GM5. Cannot locate "N" on any of the tables found on internet. When I spin the tire the drive shaft spins just a hair over two times. My first question is what gearing do I have? It's a straight 6, 3 speed on the column and I have 17 inch wheels. At 65mph I'm at 3200 rpm. I'd like to increase my highway speeds and decrease my rpm's. Which gearing should I go with? Posted via Mobile Device

04-28-2011, 11:50 AM	#2
PGSigns Senior Member Join Date: Jan 2011 Location: Hayes Va Posts: 4,569	Re: 64 c10 rear end question Going by the rpm I would say 3.73 Jimmy __________________ 60 to 66 Chevy and GMC window decals http://67-72chevytrucks.com/vboard/s...d.php?t=661131 Good friends, good food and a hotrod what else do you need? 1966 BBW long fleet Daily driver 1965 BBW short fleet Sold and going to a good home 1965 Suburban 2003 3500 Duramax 2005 Ultra Classic

04-28-2011, 02:20 PM	#3
MikeN Senior Member Join Date: Oct 2007 Location: Marietta, GA Posts: 782	Re: 64 c10 rear end question Almost 100% of 64-66 with 6-cyl and 3-sp manual are 3.73's.

04-28-2011, 06:36 PM	#4
oldtrux Registered User Join Date: Jul 2010 Location: Bancroft, ontario Posts: 554	Re: 64 c10 rear end question i would leave the 373's and put in a 5 speed od trans imho!

04-28-2011, 07:31 PM	#5
shuvl Registered User Join Date: Apr 2011 Location: naples, fl Posts: 42	Re: 64 c10 rear end question Well I took the cover off and found 4:11 gears and gear lube that didn't look like it had ever been changed. So if I want to keep the three speed what would y'all suggest I put in for gears? Posted via Mobile Device

04-28-2011, 07:59 PM	#6
fleetsidelarry Senior Car Nut Join Date: Jan 2008 Location: shellman bluff, GA Posts: 1,411	Re: 64 c10 rear end question cheapest way would be to find a 3.07. better way is to do the OD. Best way is to do the 3.73 (a common gear in our trucks) AND the OD. if I'm doing the math correctly: if you are 3200@65 now, a .7 OD gives 2240@65. the 3.07 is like a .75 OD, giving almost 2400@65. the 3.73+OD would yield ≈ 2000@65 my 3.07/700r4 (.7 OD) runs about 2000@75, more or less __________________ Larry

04-28-2011, 11:23 PM	#7
collins10672 Registered User Join Date: Jan 2009 Location: bean station tennessee Posts: 398	Re: 64 c10 rear end question the 3:07 was the highest gear available in the 64-66 trucks.kind of hard to find though.

04-29-2011, 02:22 AM	#8
Captainfab 60-66 Nut Join Date: Mar 2007 Location: Coeur d'Alene, Idaho Posts: 23,246	Re: 64 c10 rear end question The 3.42 gears are a good comprimise between the 3.73's and 3.07's __________________ Power Steering Box Adapter Plates For Sale HERE Power Brake Booster Adapter Brackets For Sale '63-'66 HERE and '67-'72 HERE and '60-'62 HERE and "60-'62 with clutch HERE Rear Disc Brake Brackets For Sale. Impala SS calipers HERE Camaro Calipers HERE D52 Calipers HERE 6 Lug HERE Hydroboost Mounting Plates HERE

04-29-2011, 11:52 AM	#9
shuvl Registered User Join Date: Apr 2011 Location: naples, fl Posts: 42	Re: 64 c10 rear end question Thanks for all the advice. That's why I like this group, its a plethora of knowledge and no BS attitudes. Posted via Mobile Device

04-29-2011, 02:35 PM	#11
Clyde65 1965 Chevy C10, 2005 4.8L/4l60 Join Date: Aug 2004 Location: DFW Texas Posts: 8,541	Re: 64 c10 rear end question If you go OD trans, pick the 3.73's if you can, if you steel a deal, 3.42's will also work with an OD trans. I have heard that the 3.08's are better for 3speed tranny's, but I have no real experience with them other than my truck now has the 3.08's and a 4 speed, I would enjoy it more if there were 3.73's or at least 3.42's back there. the only reason I am staying with the 3.08's is because I just rebuilt the rear about 3 months b4 I did my LS swap and OD trans. __________________ Clyde65 Rebuild of Clyde http://67-72chevytrucks.com/vboard/s...84#post8338184 69 Aristocrat Lo Liner build http://67-72chevytrucks.com/vboard/s...84#post7561684 *support our troops!*

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