Gears -vs- OD - The 1947 - Present Chevrolet & GMC Truck Message Board Network

67chevytodd · 02-25-2007, 10:18 PM

I currently have 3:07 gears and a solid th-350 in my 67 C-10. Randy's Ring & Pinion has 2:56 and 2:73 ring and pinions available. Like everyone else I am trying to increase fuel mileage. Are these gears to high? The 2:56 gears with 235/75/R15 @28.9in would be 1800RPM @ 60mpm very similar to 3:73's w/ same tire and auto overdrive. But the ring and pinion are much cheaper than a built 700R4. I hear alot about swaping to overdrives but nothing on gears higher that 3:08's. Any thoughts??? Thanks Todd

BCOWANWHEELS · 02-25-2007, 10:28 PM

it will be a dog on takeoff with the 2.56 gears

**Boog** · 02-25-2007, 10:40 PM

Todd I agree with BCowan. Any thing less than the 3.07 you have now will be really sluggish. The 3.07 is a good all around gear with a 3 speed trans. The 3.42 and 3.73 work well with the o/drive trans.
You can go too far with the high gear ratio and hurt the mileage you are getting now. By the way what mpg is it getting now? Is the engine in a good state of tune? Is it built with a lumpy cam, highrise intake and big carb?

hvychve · 02-25-2007, 11:42 PM

I would hate to put a load in the bed and have to take off suddenly with 2:56 gears, I would just hate that . Mileage will actually be worse, due to fact you will need more fuel to take off, dont see any improvements with that combo, I would put in a few extra hours at work and save my pop bottles for a 700. Just my opinion.

dmec · 02-26-2007, 12:19 AM

what about a 350 with a lock up converter. maybe gain a little more mpg.

stsalvage · 02-26-2007, 12:42 AM

Most people from calif and other west states don't understand why some cars and trucks from the east had 2.88 gears i found out buy being back east in the winter time you run any thing more then a 2.90 gear buy the end of winter you willneed a new truck front end and new bed sides cus you slide all over the place and the high gears are to keep you from spiining out

extd56 · 02-26-2007, 12:53 AM

My 56 Chevy truck has 2:56 gears in it out of a 79 Seville with a 402 big block and a 400 trans and I got 16MPG last year going to Reno.

1969 GMC · 02-26-2007, 01:38 AM

Quote:

Originally Posted by stsalvage

Most people from calif and other west states don't understand why some cars and trucks from the east had 2.88 gears i found out buy being back east in the winter time you run any thing more then a 2.90 gear buy the end of winter you willneed a new truck front end and new bed sides cus you slide all over the place and the high gears are to keep you from spiining out

What???

02-25-2007, 10:18 PM	#1
67chevytodd Junior Member Join Date: Aug 2003 Location: SW Nebraska Posts: 50	Gears -vs- OD I currently have 3:07 gears and a solid th-350 in my 67 C-10. Randy's Ring & Pinion has 2:56 and 2:73 ring and pinions available. Like everyone else I am trying to increase fuel mileage. Are these gears to high? The 2:56 gears with 235/75/R15 @28.9in would be 1800RPM @ 60mpm very similar to 3:73's w/ same tire and auto overdrive. But the ring and pinion are much cheaper than a built 700R4. I hear alot about swaping to overdrives but nothing on gears higher that 3:08's. Any thoughts??? Thanks Todd __________________ Old Chevys never die they are just reborn!

02-25-2007, 10:28 PM	#2
BCOWANWHEELS Registered User Join Date: Nov 2006 Location: KINGSPORT,TN. Posts: 3,035	Re: Gears -vs- OD it will be a dog on takeoff with the 2.56 gears

02-25-2007, 10:40 PM	#3
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 13,141	Re: Gears -vs- OD Todd I agree with BCowan. Any thing less than the 3.07 you have now will be really sluggish. The 3.07 is a good all around gear with a 3 speed trans. The 3.42 and 3.73 work well with the o/drive trans. You can go too far with the high gear ratio and hurt the mileage you are getting now. By the way what mpg is it getting now? Is the engine in a good state of tune? Is it built with a lumpy cam, highrise intake and big carb? __________________ Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver primer is finer 91 Chevy sportside, Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross

02-25-2007, 11:42 PM	#4
hvychve To The Levy Join Date: Jan 2007 Location: california Posts: 391	Re: Gears -vs- OD I would hate to put a load in the bed and have to take off suddenly with 2:56 gears, I would just hate that . Mileage will actually be worse, due to fact you will need more fuel to take off, dont see any improvements with that combo, I would put in a few extra hours at work and save my pop bottles for a 700. Just my opinion.

02-26-2007, 12:19 AM	#5
dmec Senior Member Join Date: Jun 2000 Location: yucaipa ca Posts: 580	Re: Gears -vs- OD what about a 350 with a lock up converter. maybe gain a little more mpg.

02-26-2007, 12:42 AM	#6
stsalvage Scrapper 1 Join Date: Jan 2007 Location: Riverside Calif Posts: 1,649	Re: Gears -vs- OD Most people from calif and other west states don't understand why some cars and trucks from the east had 2.88 gears i found out buy being back east in the winter time you run any thing more then a 2.90 gear buy the end of winter you willneed a new truck front end and new bed sides cus you slide all over the place and the high gears are to keep you from spiining out

02-26-2007, 12:53 AM	#7
extd56 Senior Member Join Date: Nov 2004 Location: Vacaville, CA Posts: 2,272	Re: Gears -vs- OD My 56 Chevy truck has 2:56 gears in it out of a 79 Seville with a 402 big block and a 400 trans and I got 16MPG last year going to Reno. Last edited by extd56; 02-26-2007 at 12:53 AM.



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