axle options - The 1947 - Present Chevrolet & GMC Truck Message Board Network

hotrod_991 · 08-13-2010, 06:33 PM

I am heading to the the pick and pull tomarrow morning searching for a diffrent rear end for my 77 c10 longbed. Does anyone know what i need to be looking for and in what veichles? Im after a 12bolt with posi and the highest gear ratio i can get 342, 373, 410. Any help is always greatly apreciated.

tucsonjwt · 08-13-2010, 11:44 PM

I'm not sure what range of years have interchangeable axles, but the only way I know to check gear ratio is to turn the rear wheels and count the revolutions of the drive shaft - might be hard to do with truck in a junkyard.
I have a 4:10 C20 with a 454 and it sucks money out of my wallet. I assume that you are aware of the lack of fuel economy, and lower top end mph when on the highway. When I was growing up, we called 4:10 and 4:56 low gears - guys put them in their 1/4 mile cars. Some call them high gears because of the high numbers.

hotrod_991 · 08-14-2010, 09:22 AM

haha yea i am fully aware of the gas mileage its is not my daily driver by any means just my toy. Found out I have a 2:08 ratio wich is really making my 357 small block and big cam cranky. thank you for the help bud.

karl · 08-16-2010, 06:55 PM

Unless your towing, the 3.42 is plenty of gear. Ive got a mild 350 and i can get a second gear scratch with 3.07s. Thats with 295/50/15 on back.

LONGHAIR · 08-16-2010, 07:26 PM

Quote:

Originally Posted by hotrod_991

Found out I have a 2:08 ratio wich is really making my 357 small block and big cam cranky.

2.08? How did you come up with that?
The highest I have ever seen is 2.56

hotrod_991 · 08-16-2010, 08:43 PM

i did the tire rotation trick and one rotation of the tire gets me just shy of 2 turns. If I am mistaken please set me straight. Although I have to say I did that on several rear ends at the pick and pull and seem slike out of 10 truck they all turned the same amount im lil cofused if I am doing it right or not.

*nbpro* · 08-16-2010, 09:46 PM

you need to mark where your driveshaft and wheel are to begin and count how many times each make a full revolution until they return to the original position, that should get you real close. Math differs if it's a posi or open rear

karl · 08-17-2010, 03:27 AM

Now if your going to be running tall tires or 4x4 setup the 3.73-4.11 may be the ticket. You really need to consider the tallness of the tire. For street with a normal or low profile tire 3.42 if more than enough. 3.07 is great all around highway and town gear for normal size tire.

hotrod_991 · 08-17-2010, 05:24 AM

i run 255/60/15's out back but am going taller here soon with a 275/70/15 i think. its not my daily jus a toy that i enjoy from time to time so 3.73 or close to em will be alot of fun to play with. thanks for all the help everyone

08-13-2010, 06:33 PM	#1
hotrod_991 Registered User Join Date: Jul 2009 Location: Thibodaux, LA Posts: 479	axle options I am heading to the the pick and pull tomarrow morning searching for a diffrent rear end for my 77 c10 longbed. Does anyone know what i need to be looking for and in what veichles? Im after a 12bolt with posi and the highest gear ratio i can get 342, 373, 410. Any help is always greatly apreciated. __________________ "Buckle up I wanna try somethin!!" "of course it will hold!, I welded it!" 1977 c10 under knife for full rebuild, 5.3l 4l60e drive rain swap, replacement frame and green repaint

08-13-2010, 11:44 PM	#2
tucsonjwt Registered User Join Date: Jul 2007 Location: Tucson, AZ Posts: 3,189	Re: axle options I'm not sure what range of years have interchangeable axles, but the only way I know to check gear ratio is to turn the rear wheels and count the revolutions of the drive shaft - might be hard to do with truck in a junkyard. I have a 4:10 C20 with a 454 and it sucks money out of my wallet. I assume that you are aware of the lack of fuel economy, and lower top end mph when on the highway. When I was growing up, we called 4:10 and 4:56 low gears - guys put them in their 1/4 mile cars. Some call them high gears because of the high numbers.

08-14-2010, 09:22 AM	#3
hotrod_991 Registered User Join Date: Jul 2009 Location: Thibodaux, LA Posts: 479	Re: axle options haha yea i am fully aware of the gas mileage its is not my daily driver by any means just my toy. Found out I have a 2:08 ratio wich is really making my 357 small block and big cam cranky. thank you for the help bud. __________________ "Buckle up I wanna try somethin!!" "of course it will hold!, I welded it!" 1977 c10 under knife for full rebuild, 5.3l 4l60e drive rain swap, replacement frame and green repaint

08-16-2010, 06:55 PM	#4
karl Registered User Join Date: Dec 2004 Location: grand terrace , caifornia Posts: 338	Re: axle options Unless your towing, the 3.42 is plenty of gear. Ive got a mild 350 and i can get a second gear scratch with 3.07s. Thats with 295/50/15 on back. Last edited by karl; 08-16-2010 at 06:56 PM.

08-16-2010, 08:43 PM	#6
hotrod_991 Registered User Join Date: Jul 2009 Location: Thibodaux, LA Posts: 479	Re: axle options i did the tire rotation trick and one rotation of the tire gets me just shy of 2 turns. If I am mistaken please set me straight. Although I have to say I did that on several rear ends at the pick and pull and seem slike out of 10 truck they all turned the same amount im lil cofused if I am doing it right or not. __________________ "Buckle up I wanna try somethin!!" "of course it will hold!, I welded it!" 1977 c10 under knife for full rebuild, 5.3l 4l60e drive rain swap, replacement frame and green repaint

08-16-2010, 09:46 PM	#7
nbpro Account Suspended Join Date: Dec 2008 Location: Huntsville,AL Posts: 2,119	Re: axle options you need to mark where your driveshaft and wheel are to begin and count how many times each make a full revolution until they return to the original position, that should get you real close. Math differs if it's a posi or open rear Last edited by nbpro; 08-16-2010 at 11:42 PM.

08-17-2010, 03:27 AM	#8
karl Registered User Join Date: Dec 2004 Location: grand terrace , caifornia Posts: 338	Re: axle options Now if your going to be running tall tires or 4x4 setup the 3.73-4.11 may be the ticket. You really need to consider the tallness of the tire. For street with a normal or low profile tire 3.42 if more than enough. 3.07 is great all around highway and town gear for normal size tire.

08-17-2010, 05:24 AM	#9
hotrod_991 Registered User Join Date: Jul 2009 Location: Thibodaux, LA Posts: 479	Re: axle options i run 255/60/15's out back but am going taller here soon with a 275/70/15 i think. its not my daily jus a toy that i enjoy from time to time so 3.73 or close to em will be alot of fun to play with. thanks for all the help everyone __________________ "Buckle up I wanna try somethin!!" "of course it will hold!, I welded it!" 1977 c10 under knife for full rebuild, 5.3l 4l60e drive rain swap, replacement frame and green repaint



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