The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - What would give better mpg? Taller gears or OD?

79BIG10 · 12-02-2005, 02:22 AM

Good question there. I think it matters in the way you drive. Do you drive alot of city driving or highway driving? Reason I say this is that I've had 3.07 with my TH350 and now I have 3.73 with the TH350. I get less mileage on the highway but around town running lower RPM I've gotten about the same. With a 700r4 and you're using OD then a 3.42 would be a good choice. 3.07 is awful off the line even with a 700r4 high geared 1st gear. My truck was great at highway speeds running lower RPM but taking off it took longer to get up to speed.

My suggestion is go with 3.42 and 700r4 if you have alot of highway driving. If not stick with the TH350 and 3.42 setup. I think you'll not like going with the 3.07 setup.

12-02-2005, 02:22 AM	#2
79BIG10 I'm back with 2nd truck! Join Date: Feb 2002 Location: Texas Posts: 3,774	Re: What would give better mpg? Taller gears or OD? Good question there. I think it matters in the way you drive. Do you drive alot of city driving or highway driving? Reason I say this is that I've had 3.07 with my TH350 and now I have 3.73 with the TH350. I get less mileage on the highway but around town running lower RPM I've gotten about the same. With a 700r4 and you're using OD then a 3.42 would be a good choice. 3.07 is awful off the line even with a 700r4 high geared 1st gear. My truck was great at highway speeds running lower RPM but taking off it took longer to get up to speed. My suggestion is go with 3.42 and 700r4 if you have alot of highway driving. If not stick with the TH350 and 3.42 setup. I think you'll not like going with the 3.07 setup. __________________ 1979 Chevrolet Bonanza Big10 "Tootsie Roll" 1985 Chevrolet Silverado (wife's) Member of the Southern Bowties Club "Don't underestimate how sexy a fat man who drinks to excess can be." Homer Simpson