Which ratio to look for? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

krue · 01-15-2008, 01:28 PM

I just put a 200-4R in my truck and the 3.07 gears are waaaay too tall. I'm running a ~30" tire and at 60 mph I'm only turning 1500-1600 rpm's in overdrive. I've got a rear with 3.40 gears but I think that may still be too tall. Would a 3.73 be a better choice? I would like some low end, I still use my truck like a truck and pull an old tractor around every now and then.

67_C-30 · 01-15-2008, 01:35 PM

In my experience the 3.73 is the best all around with the OD trannys. If you aren't going any bigger than the than the 30" tires I'd go with it. Anything much bigger, I'd step up to 4.10's. The trucks I've had (80's and 90's Chevys) with OD's and 3.08's got much worse mileage with 3.08's than they did when I put 3.73's in them. The high geared, OD trucks were so gutless that I stayed in the throttle just trying to feel the truck under me, if that makes sense. Without a decent gear, the convertor unlocks if the wind blows slightly, and they sound like crap going down the road 50 mph at basically idle speed!

Longhorn Man · 01-15-2008, 01:37 PM

3.73 ... i agree 100%

**Boog** · 01-15-2008, 03:14 PM

Hey Krue. I was just playing with the Richmond Gear calculator and plugged in your setup. That is way high geared especially if you do some hauling. That 3.07 with OD brings the final drive ratio down to something like a 2.30 something. A 3.73 gear will bring your rpm's up to around 1800 @ 60 mph. That's a good bit closer to the sweet spot of the small block. It will tow better and maybe get better mileage too.

Give it a looksee. http://www.richmondgear.com/streetcalculators.html

**Palf70Step** · 01-15-2008, 03:21 PM

We should have left that 3.73 at your place Krue, and now I don't have it no more to give it to you.

Krue my 96 GMC had the 3.42 with OD and it was pretty sweet. I think either would work fine.

01-15-2008, 01:28 PM	#1
krue Designated A-hole! Join Date: Mar 2003 Location: South Mississippi Posts: 36,450	Which ratio to look for? I just put a 200-4R in my truck and the 3.07 gears are waaaay too tall. I'm running a ~30" tire and at 60 mph I'm only turning 1500-1600 rpm's in overdrive. I've got a rear with 3.40 gears but I think that may still be too tall. Would a 3.73 be a better choice? I would like some low end, I still use my truck like a truck and pull an old tractor around every now and then. __________________ "If it ain't broke, fix it 'til it is!" Being stupid ain't illegal. We're Still Debt Free Except for the House!!! www.daveramsey.com 70 GMC SWB Stepside project "Green Booger" soon to be 6.0l/4l80e 93 S-10 "Poppaw's Truck"

01-15-2008, 01:35 PM	#2
67_C-30 I have a radical idea! Join Date: Jan 2005 Location: Sweet Home Alabama! Posts: 6,513	Re: Which ratio to look for? In my experience the 3.73 is the best all around with the OD trannys. If you aren't going any bigger than the than the 30" tires I'd go with it. Anything much bigger, I'd step up to 4.10's. The trucks I've had (80's and 90's Chevys) with OD's and 3.08's got much worse mileage with 3.08's than they did when I put 3.73's in them. The high geared, OD trucks were so gutless that I stayed in the throttle just trying to feel the truck under me, if that makes sense. Without a decent gear, the convertor unlocks if the wind blows slightly, and they sound like crap going down the road 50 mph at basically idle speed! __________________ '67 C-30 Dually Pickup 6.2 Turbo Diesel, NP435 ‘72 C-10 SWB , 350 4bbl, TH350 '69 C-10 SWB , 250 L6, 3 OTT '69 GMC C3500, dump truck, 351 V6, NP435 '84 M1009 CUCV Military Blazer 67 C-30 Turbodiesel build thread http://67-72chevytrucks.com/vboard/s...d.php?t=254096 My trucks http://s226.photobucket.com/albums/d...ediafilter=all Member of the 1-Ton Club! Last edited by 67_C-30; 01-15-2008 at 01:36 PM.

01-15-2008, 01:37 PM	#3
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Which ratio to look for? 3.73 ... i agree 100%

01-15-2008, 03:14 PM	#4
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 13,452	Re: Which ratio to look for? Hey Krue. I was just playing with the Richmond Gear calculator and plugged in your setup. That is way high geared especially if you do some hauling. That 3.07 with OD brings the final drive ratio down to something like a 2.30 something. A 3.73 gear will bring your rpm's up to around 1800 @ 60 mph. That's a good bit closer to the sweet spot of the small block. It will tow better and maybe get better mileage too. Give it a looksee. http://www.richmondgear.com/streetcalculators.html __________________ Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver primer is finer 91 Chevy sportside, Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross

01-15-2008, 03:21 PM	#5
Palf70Step State of Confusion! Join Date: Jul 2002 Location: Gulfport, MS USA Posts: 47,083	Re: Which ratio to look for? We should have left that 3.73 at your place Krue, and now I don't have it no more to give it to you. Krue my 96 GMC had the 3.42 with OD and it was pretty sweet. I think either would work fine. __________________ Bill 1970 Chevy Custom/10 LWB Fleetside 2010 Toyota Tacoma PreRunner SR5 Double Cab - DD Member of Louisiana Classic Truck Club (LCTC) Bill's Gallery Life isn't tied with a bow, but it's still a gift. Live simply. Love generously. Care deeply. Speak kindly. Leave the rest to God! Last edited by Palf70Step; 01-15-2008 at 03:22 PM.



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