What's the difference in diferentials? or What ratio Horatio? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Hilandr451 · 10-21-2005, 11:35 AM

Hey fellas,
As usual, I'm sitting here contemplating rear-ends....for my truck that is. What I've got is a C20 with a "mutt 327" power plant that I'm building for a daily driver and a tow vehicle for my 26' vintage Airstream trailer. I'm thinking of running a 700r4 in front of a 'Gear Vendors' gear splitter at stock height with 16" rims & close to stock tires.

I have a really low geared differential in it now (60MPH @ 3-1/2 grand tops) and I was wondering what gear ratio would be ideal for what I want to do with the truck. I'll be doing a great deal of highway driving, but mountain passes & campground manouvering should be considered as well.

Economy, of course, is a big concern here and I would like to be able to cruise at 75 when I'm not hooked up to the trailer

- at the same time, I don't want to loose all of my torque off the line. Anybody know about ratios? Any advice would be great.

**special-K** · 10-22-2005, 01:16 PM

With all that o/d you`d want to keep the rear ratio low,Joe.That`s what my book says,Hernandez.

Fred T · 10-23-2005, 02:04 AM

Something's not adding up here. Your ratio should be 4.57, stock for a C-20 with 4 speed. But to get that and the numbers you gave to work the tire size has to be 26". Far from stock. The 5.14 gears come up with your numbers using a 30" tire.

I would recommend the OD tranny, but now the second splitter.

64fleetside · 10-23-2005, 10:31 AM

I would run a pumpkin from 70-72 3/4 ton auto, most of these were 4.10, using a 700R4 would pull great & get decent mileage. I like the GV unit, just $2k is hard to swallow, there was good 700 in a wrecked 94 c1500 at U-pull-it for $300 yesterday. My 2 cents, Brian

rwgregory · 10-25-2005, 03:04 AM

If it were me, I would go with either a 3:73 or 4:10 rear gear and run tall 33"
rear tires. FYI: 33" tires w/ 4:10 rear gears = 2600 rpm with trans in high
gear (1 to 1 ratio).

10-21-2005, 11:35 AM	#1
Hilandr451 Registered User Join Date: Oct 2005 Location: Houston Texas Posts: 316	What's the difference in diferentials? or What ratio Horatio? Hey fellas, As usual, I'm sitting here contemplating rear-ends....for my truck that is. What I've got is a C20 with a "mutt 327" power plant that I'm building for a daily driver and a tow vehicle for my 26' vintage Airstream trailer. I'm thinking of running a 700r4 in front of a 'Gear Vendors' gear splitter at stock height with 16" rims & close to stock tires. I have a really low geared differential in it now (60MPH @ 3-1/2 grand tops) and I was wondering what gear ratio would be ideal for what I want to do with the truck. I'll be doing a great deal of highway driving, but mountain passes & campground manouvering should be considered as well. Economy, of course, is a big concern here and I would like to be able to cruise at 75 when I'm not hooked up to the trailer - at the same time, I don't want to loose all of my torque off the line. Anybody know about ratios? Any advice would be great. __________________ Greg Smith a.k.a. "The Highlander" 1966 C20 Custom Camper, 2017 Chevy Silverado 1500 Highlander's Project Pics Highlander's web site: www.6066ChevyTrucks.com

10-22-2005, 01:16 PM	#2
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,858	Re: What's the difference in diferentials? or What ratio Horatio? With all that o/d you`d want to keep the rear ratio low,Joe.That`s what my book says,Hernandez. __________________ "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 ~

10-23-2005, 02:04 AM	#3
Fred T Cantankerous Geezer Join Date: Aug 2002 Location: Bel Aire, KS Posts: 6,264	Re: What's the difference in diferentials? or What ratio Horatio? Something's not adding up here. Your ratio should be 4.57, stock for a C-20 with 4 speed. But to get that and the numbers you gave to work the tire size has to be 26". Far from stock. The 5.14 gears come up with your numbers using a 30" tire. I would recommend the OD tranny, but now the second splitter. __________________ Fred There is no such thing as too much cam...just not enough engine.

10-23-2005, 10:31 AM	#4
64fleetside Registered User Join Date: Apr 2004 Location: arkieland Posts: 1,070	Re: What's the difference in diferentials? or What ratio Horatio? I would run a pumpkin from 70-72 3/4 ton auto, most of these were 4.10, using a 700R4 would pull great & get decent mileage. I like the GV unit, just $2k is hard to swallow, there was good 700 in a wrecked 94 c1500 at U-pull-it for $300 yesterday. My 2 cents, Brian

10-25-2005, 03:04 AM	#5
rwgregory Registered User Join Date: Apr 2005 Location: Chula Vista, California Posts: 495	Re: What's the difference in diferentials? or What ratio Horatio? If it were me, I would go with either a 3:73 or 4:10 rear gear and run tall 33" rear tires. FYI: 33" tires w/ 4:10 rear gears = 2600 rpm with trans in high gear (1 to 1 ratio). __________________ rwgregory 67 GMC 2500 ,2w/d wide box 305 V-6, 4-speed



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