Differential Gearing 4:11? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

crowballs · 01-03-2011, 09:30 PM

The truck I have is in the signature. I have 15" 305's with 3:42 gears in it and was wondering if it would be advisable to change them, and if so to what? The reason I ask, I was towing a very light load the other day and noticed it took a hell of a lot to keep her up to speed on some of the SOCAL mountains, and outside of general horsepower, would my ratio be more of the problem than I originally thought, also my gas mileage is crap, but it is a 350, but the pulling really got my goat. Thanks for any input!

Blue Rat · 01-03-2011, 09:44 PM

How tall are the 305's?

crowballs · 01-03-2011, 10:52 PM

Quote:

Originally Posted by Blue Rat

How tall are the 305's?

33". That's using an online calculator for that, but it feels appropriate.

**special-K** · 01-04-2011, 09:30 AM

I'm not sure what to tell you. 3.42 isn't such a tall gear to dog out a truck for hauling nor are 33s so tall to have a great effect. My '72 with 3.54s and 33s hauls with plenty of mite. Some of your lack of power is probably due to being in o/d. I know you said a light load. I've been driving an '89 K1500 with 350/700r4 for a couple weeks and empty it seems pretty doggie on hills to me. The power's there,but to stay at 70 on a grade it kicks down out of o/d. I figure the gears are something lame,like taller than 3.08 into the 2s. Do you run those mountains a lot? That's another consideration. Unless it was a regular problem I wouldn't change gears for that. I do like 4.10s with o/d in my '92 with 6.5TD/NV4500,though. That thing takes any hill in o/d no problem and that truck weighs close to 8,000# at any given time.

lurch115 · 01-06-2011, 12:34 AM

honestly, if you are wanting to change gears i would try going to a 3.73 gear unless its not a daily driver. then i would choose 4.11 gears. the thing i think you will still find out though is that the 5th gear in that 5 spd is still gonna be doggy though because it tends to be a "tall gear" transmission wise.

01-03-2011, 09:30 PM	#1
crowballs Registered User Join Date: May 2010 Location: San Diego, CA Posts: 33	Differential Gearing 4:11? The truck I have is in the signature. I have 15" 305's with 3:42 gears in it and was wondering if it would be advisable to change them, and if so to what? The reason I ask, I was towing a very light load the other day and noticed it took a hell of a lot to keep her up to speed on some of the SOCAL mountains, and outside of general horsepower, would my ratio be more of the problem than I originally thought, also my gas mileage is crap, but it is a 350, but the pulling really got my goat. Thanks for any input! __________________ 1990 K1500 / 170,000 miles 350 w/670cfm Holley TBI 5-speed Tranny Otherwise, all stock. Last edited by crowballs; 01-03-2011 at 11:22 PM. Reason: screwed up the ratio

01-03-2011, 09:44 PM	#2
Blue Rat Registered User Join Date: Dec 2010 Location: Arkansas Posts: 608	Re: Differential Gearing 4:11? How tall are the 305's?

01-04-2011, 09:30 AM	#4
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,851	Re: Differential Gearing 4:11? I'm not sure what to tell you. 3.42 isn't such a tall gear to dog out a truck for hauling nor are 33s so tall to have a great effect. My '72 with 3.54s and 33s hauls with plenty of mite. Some of your lack of power is probably due to being in o/d. I know you said a light load. I've been driving an '89 K1500 with 350/700r4 for a couple weeks and empty it seems pretty doggie on hills to me. The power's there,but to stay at 70 on a grade it kicks down out of o/d. I figure the gears are something lame,like taller than 3.08 into the 2s. Do you run those mountains a lot? That's another consideration. Unless it was a regular problem I wouldn't change gears for that. I do like 4.10s with o/d in my '92 with 6.5TD/NV4500,though. That thing takes any hill in o/d no problem and that truck weighs close to 8,000# at any given time. __________________ "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 ~

01-06-2011, 12:34 AM	#5
lurch115 Registered User Join Date: Oct 2006 Location: iowa Posts: 722	Re: Differential Gearing 4:11? honestly, if you are wanting to change gears i would try going to a 3.73 gear unless its not a daily driver. then i would choose 4.11 gears. the thing i think you will still find out though is that the 5th gear in that 5 spd is still gonna be doggy though because it tends to be a "tall gear" transmission wise. __________________ "Horsepower is how fast you hit the wall, torque is how far you carry the wall with you." '84 chevy half ton short box 2wd, 67,000 actual miles '03 chevy 1500 HD crew cab 4x4 standard box, 6.0L

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