4.57 standard gear ratio? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

65standard · 03-05-2015, 08:46 PM

I have a 1970 C20 with a 250 and 4-speed setup. I just read in the original sales brochure that the standard gear ratio is 4.57 in this truck and the 4.10 and 3.54 were optional. Is this correct? I guess it is a good thing I bought the original size 7.50-16 tires to keep the RPMs under the moon.

Wonder why the C20's standard ratio is 4.57 and the C10's standard ratio is 3.73.

Mike C · 03-05-2015, 08:58 PM

Takes more gear for the same engine to do the increased work that was capable with the C20.

If you have the Dana rear axle and no one has tossed it when they changed the fluid, it will have a ratio tag that tells you what you have. Not the case on the HO52 (which is more likely the rear you have installed.)

**special-K** · 03-05-2015, 08:59 PM

C/20s needed more torque from the 250. The 4.10 was as high (tall) of a gear as it went, except the 402s automatics that came with 3.54s (Dana60-only). Don't forget, it wasn't so unusual to find 3.73s or 4.10 factory gears in muscle cars, so a truck with 4.57s is not far off of that. Engines were run at higher RPMs back then

hamjet · 03-05-2015, 09:04 PM

http://67-72chevytrucks.com/vboard/s...15692&posted=1 Heres a link, but I don't see 1970 C20...

**Jason Banks** · 03-05-2015, 09:04 PM

I have a 250 with 4.11 rear gears and it's pushing it to do 70 on the highway. I can't imagine 4.57

03-05-2015, 08:46 PM	#1
65standard Registered User Join Date: Dec 2014 Location: Coal City, IL Posts: 695	4.57 standard gear ratio? I have a 1970 C20 with a 250 and 4-speed setup. I just read in the original sales brochure that the standard gear ratio is 4.57 in this truck and the 4.10 and 3.54 were optional. Is this correct? I guess it is a good thing I bought the original size 7.50-16 tires to keep the RPMs under the moon. Wonder why the C20's standard ratio is 4.57 and the C10's standard ratio is 3.73. __________________ Tony Nicholas @ Midwest Metal Masters 1953 Chevy 3100 392 Hemi w/727 & 9” Ford 1985 Chevy C/10 6.0L 4L80 373 locker

03-05-2015, 08:58 PM	#2
Mike C Registered User Join Date: Dec 1999 Location: Austin, TX, USA Posts: 7,734	Re: 4.57 standard gear ratio? Takes more gear for the same engine to do the increased work that was capable with the C20. If you have the Dana rear axle and no one has tossed it when they changed the fluid, it will have a ratio tag that tells you what you have. Not the case on the HO52 (which is more likely the rear you have installed.) __________________ 44 Willys MB 52 M38A1 64 Corvette Coupe 68 Camaro 'vert LT1 & TH700 69 Z/28 355 12.6's @110 69 Chevy Short Step 4 1/2"/7" drop 72 Jimmy 4WD 4spd 4" & 35's 02 GMC 2500HD 4x4 Duramax

03-05-2015, 08:59 PM	#3
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,851	Re: 4.57 standard gear ratio? C/20s needed more torque from the 250. The 4.10 was as high (tall) of a gear as it went, except the 402s automatics that came with 3.54s (Dana60-only). Don't forget, it wasn't so unusual to find 3.73s or 4.10 factory gears in muscle cars, so a truck with 4.57s is not far off of that. Engines were run at higher RPMs back then __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~

03-05-2015, 09:04 PM	#4
hamjet Registered User Join Date: Apr 2013 Location: South Westerlo, New York Posts: 1,325	Re: 4.57 standard gear ratio? http://67-72chevytrucks.com/vboard/s...15692&posted=1 Heres a link, but I don't see 1970 C20... __________________ Thanks, Joe.. 1969 C/10, 348 C.I., 3X2 bbl. V8, 2004r , LWB.

03-05-2015, 09:04 PM	#5
Jason Banks Senior Member Join Date: Dec 1999 Location: TX Posts: 1,637	Re: 4.57 standard gear ratio? I have a 250 with 4.11 rear gears and it's pushing it to do 70 on the highway. I can't imagine 4.57



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