Simple gear ratio question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

qpjeffc · 04-28-2005, 10:27 AM

Just a quick question, are 4:11 and 4:10 ratios the same? I have heard a lot of differing opions on this so I thought you guys would know for sure. I have a 14bff that I want to install with 4:10 stamped on it and my front is 4:11? Thanks, Jeff

**Stocker** · 04-28-2005, 11:25 AM

Not positive, but I am fairly sure they are not the same. I believe 4.10 has 41 teeth on the ring and 10 on the pinion, and 4.11 has 37 on the ring and 9 on the pinion. Since 4.11 has fewer teeth, they will be larger, and therefore stronger. At least that's what I recall hearing back in my old hot-roddin' days!

Rod · 04-28-2005, 11:52 AM

Its not going to make any real difference ..theres usually a little difference between front and rear ratios anyway. Like a 4.10 rear with 4.09 front...or 4.57 rear with 4.55 front. Those are typical 67-72 truck numbers anyway. I take it your swapping the whole diff. You may run into problems trying to interchange different brand axle gears into different brand housings. You really didn't explain enough.

1969 GMC · 04-28-2005, 03:12 PM

They are not the same, because they have different ring and pinion tooth count #'s.

The 14 bolt that I bought, for example, has 4.09 gears (45 on the ring gear and 11 on the pinion).
there are also the more common 4.10's which have 41 teeth on the ring gear and 10 on the pinion.

**Yukon Jack** · 04-28-2005, 03:34 PM

Like said above, it is normal for the front axle to be slightly different than the rear axle. Like in my 69 K20, one axle is 4.56 and the other is 4.57.

1969K10 · 05-03-2005, 10:03 AM

Friend of mine has a Dodge Dakota, and there is a huge warning label not to drive it on paved surface. I was told the reason being, those trucks are set up with 4.10's in the front & 4.11's in the rear. that way when locked in, the front is always pulling, and the rear just has to keep up...

Mudder · 05-03-2005, 11:38 AM

Its pretty common for theme to be a number off. A lot of mud racers like the front higher so that the rear doesnt try to pass the front.

Jason915 · 05-03-2005, 12:39 PM

Yeah typically you want your front to pull forward somewhat, like mudder67 said so the rear don't try to pass you up. Nothing wrong with running the same exact ratio in the front and rear 4.10/4.10 or 4.09/4.11, 4.10/4.11 just make sure that the higher ratio is in front.

04-28-2005, 10:27 AM	#1
qpjeffc Registered User Join Date: Oct 2004 Location: Edmonton, Alberta Posts: 27	Simple gear ratio question Just a quick question, are 4:11 and 4:10 ratios the same? I have heard a lot of differing opions on this so I thought you guys would know for sure. I have a 14bff that I want to install with 4:10 stamped on it and my front is 4:11? Thanks, Jeff

04-28-2005, 11:25 AM	#2
Stocker 20' Daredevil (Ret) Join Date: May 2003 Location: Jefferson State Posts: 13,722	Not positive, but I am fairly sure they are not the same. I believe 4.10 has 41 teeth on the ring and 10 on the pinion, and 4.11 has 37 on the ring and 9 on the pinion. Since 4.11 has fewer teeth, they will be larger, and therefore stronger. At least that's what I recall hearing back in my old hot-roddin' days! __________________ - Mike - 1972 K20 LWB 350/350/205 RIP El Jay

04-28-2005, 11:52 AM	#3
Rod Join Date: Dec 1999 Location: Eastern - Manitoba Canada, Winnipeg Posts: 4,369	Its not going to make any real difference ..theres usually a little difference between front and rear ratios anyway. Like a 4.10 rear with 4.09 front...or 4.57 rear with 4.55 front. Those are typical 67-72 truck numbers anyway. I take it your swapping the whole diff. You may run into problems trying to interchange different brand axle gears into different brand housings. You really didn't explain enough. __________________ Senior active founding member. 70 3/4 ton GMC Suburban 4x4 250/4 spd. 71 1/2 ton Suburban Chevy 4x4, 350/350 72 Chev 1 ton tow truck 402BB w/Holmes 440 wrecker on propane 2005 FLSTSCI Harley Springer 85 FXSB Harley Lowrider 72 Triumph 650 Bonneville 5spd "Poor people don't have hobbies" Quote from wife.

04-28-2005, 03:12 PM	#4
1969 GMC Registered User Join Date: Feb 2003 Location: The Rubber City Posts: 5,498	They are not the same, because they have different ring and pinion tooth count #'s. The 14 bolt that I bought, for example, has 4.09 gears (45 on the ring gear and 11 on the pinion). there are also the more common 4.10's which have 41 teeth on the ring gear and 10 on the pinion. __________________ 1969 GMC K2500 1996 Honda Accord 2007 Kawasaki KLR 650 Last edited by 1969 GMC; 04-28-2005 at 03:15 PM.

04-28-2005, 03:34 PM	#5
Yukon Jack Post Whore Join Date: Feb 2000 Location: Rose Hill, KS, USA Posts: 12,686	Like said above, it is normal for the front axle to be slightly different than the rear axle. Like in my 69 K20, one axle is 4.56 and the other is 4.57. __________________ 1970 Blazer with a 400 sbc and 4" lift 1980 Pontiac Trans Am, 455 Oldsmobile 2012 Kawasaki Concours 14

05-03-2005, 10:03 AM	#6
1969K10 Senior Member Join Date: Jul 2004 Location: Clarks Hill, Indiana Posts: 733	Friend of mine has a Dodge Dakota, and there is a huge warning label not to drive it on paved surface. I was told the reason being, those trucks are set up with 4.10's in the front & 4.11's in the rear. that way when locked in, the front is always pulling, and the rear just has to keep up... __________________ 1969 K10 - V8, 465, 205, 12 bolt, D44 2002-current 1969 K20 - V8, 465, 221, Eaton, D44 2012-current Nothin' but drums on all 4 corners! past horses in the stable 72 C10-short step (97-02), 68 C10-long fleet (06-12)

05-03-2005, 11:38 AM	#7
Mudder Registered User Join Date: Feb 2001 Location: East Central, MO Posts: 11,336	Its pretty common for theme to be a number off. A lot of mud racers like the front higher so that the rear doesnt try to pass the front.

05-03-2005, 12:39 PM	#8
Jason915 Registered User Join Date: Jan 2005 Location: Colorado Springs Posts: 693	Yeah typically you want your front to pull forward somewhat, like mudder67 said so the rear don't try to pass you up. Nothing wrong with running the same exact ratio in the front and rear 4.10/4.10 or 4.09/4.11, 4.10/4.11 just make sure that the higher ratio is in front. __________________ 1971 GMC K1500 SWB Fleetside, 4" skyjacker softride and, 14 Bolt FF, HD Dana 44 4.10's 1970 K5 TBI conversion lifted etc SOLD 1968 C20 camper truck SOLD “To ban guns because criminals use them is to tell the innocent and law-abiding that their rights and liberties depend not on their own conduct, but on the conduct of the guilty and the lawless.” Jeff Snyder

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