Highest ratio gears usable?? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

airbrushguy · 10-03-2016, 12:05 AM

I would like to change my ring and pinion to higher (lower numerically) ratio. I have a 350-300 hp with auto. Truck is almost never used for hauling and winds a lot on highway. I think it has 4:11s now.
Anybody change theirs with success?

**biketopia** · 10-03-2016, 09:47 AM

3:08s is what most these trucks came with stock. A lot of guys like 3:73's, give a little more umph off the line but doesn't send your rev's through the roof. I have 3:73's in my truck and love em.

joeydurango · 10-03-2016, 09:49 AM

I have 3.73's in my 4x4, but if I were driving a lot of highway miles over 55mph, I'd probably look into a set of 3.42's.

**bigmac73** · 10-03-2016, 11:48 AM

is a 3:55 available for the 12 bolt? it is a good ratio

airbrushguy · 10-03-2016, 02:20 PM

Quote:

Originally Posted by bigmac73

is a 3:55 available for the 12 bolt? it is a good ratio

Yeah I agree, I have seen 3:42s offered and as long as it wouldn't make the automatic trans take forever to shift, I'm going to do it!
Posted via Mobile Device

Mrturner1 · 10-03-2016, 03:25 PM

4.56's with a Gear Vendors over/underdrive, perfect lol

**truckster** · 10-03-2016, 03:54 PM

You don't mention your tire size. That's a critical component in determining what your final drive ratio will be.

71meangreenc10 · 10-03-2016, 04:20 PM

I put 3.42's in mine and with OD it works well on the interstate. If you have 4.11's now, you will have to change your carrier to a 3 series carrier. Someone else can chime in on that one...

Smitty

airbrushguy · 10-05-2016, 11:10 AM

Quote:

Originally Posted by 71meangreenc10

I put 3.42's in mine and with OD it works well on the interstate. If you have 4.11's now, you will have to change your carrier to a 3 series carrier. Someone else can chime in on that one...

Smitty

Could somebody explain that more?
Thanks
Posted via Mobile Device

**HO455** · 10-05-2016, 11:21 AM

Quote:

Originally Posted by airbrushguy

Could somebody explain that more?
Thanks
Posted via Mobile Device

This is a good reference showing tire size, gear ratio and expected use/results.

http://www.4wheelparts.com/off-road/...-diameter.aspx

Bigdav160 · 10-05-2016, 11:58 AM

Because as the pinion gear gets smaller the ring gear mounting on the differential case has to move over.

AnotherWs6 · 10-05-2016, 12:01 PM

Tire size is important, agreed. What do you have OP?

Think I've got a 235/70/15 along with 3.08's. Allows me to cruise at 70mph no problem.

firedemon · 10-05-2016, 07:58 PM

Quote:

Originally Posted by airbrushguy

Yeah I agree, I have seen 3:42s offered and as long as it wouldn't make the automatic trans take forever to shift, I'm going to do it!
Posted via Mobile Device

you can get an adjustable modulator valve and change the shift points but it should be fine

firedemon · 10-05-2016, 08:10 PM

Quote:

Originally Posted by airbrushguy

Could somebody explain that more?
Thanks
Posted via Mobile Device

as the gear ratio goes up or down the size of the gears go up or down so the carrier needs to get sized to fit the ring gear series 4 carrier does 373 to 411 or higher and series 3 carrier goes from 308 to 342 . I can never remember witch but one set wont fit the carrier at all and the other set will slide down the carrier but the bolt holes will be way off

airbrushguy · 10-05-2016, 10:00 PM

Quote:

Originally Posted by firedemon

as the gear ratio goes up or down the size of the gears go up or down so the carrier needs to get sized to fit the ring gear series 4 carrier does 373 to 411 or higher and series 3 carrier goes from 308 to 342 . I can never remember witch but one set wont fit the carrier at all and the other set will slide down the carrier but the bolt holes will be way off

Thanks for clearing that up.

10-03-2016, 12:05 AM	#1
airbrushguy Registered User Join Date: May 2010 Location: hawthorne, nj Posts: 217	Highest ratio gears usable?? I would like to change my ring and pinion to higher (lower numerically) ratio. I have a 350-300 hp with auto. Truck is almost never used for hauling and winds a lot on highway. I think it has 4:11s now. Anybody change theirs with success?

10-03-2016, 09:47 AM	#2
biketopia Senior Member Join Date: Jul 2015 Location: Warrenton VA Posts: 1,105	Re: Highest ratio gears usable?? 3:08s is what most these trucks came with stock. A lot of guys like 3:73's, give a little more umph off the line but doesn't send your rev's through the roof. I have 3:73's in my truck and love em. __________________ 71 c-10 Long Bed, under the knife for a No Limit Engineering Wide Ride Chassis Pack and coil over static drop. 07 Silverado Classic 2wd 95 Camaro 427SBC/TH350

10-03-2016, 09:49 AM	#3
joeydurango Registered User Join Date: Dec 2013 Location: Durango, CO Posts: 827	Re: Highest ratio gears usable?? I have 3.73's in my 4x4, but if I were driving a lot of highway miles over 55mph, I'd probably look into a set of 3.42's. __________________ 1972 K10 Cheyenne Super \| LWB, fleetside \| 350/350/205 \| KEEPER 1971 K10 Cheyenne \| SWB, fleetside \| LS Swap 5.3/4L60 \| SOLD 1976 Trans Am \| 400/4-spd \| SOLD 1976 Trans Am \| 455/4-spd \| TOTALED

10-03-2016, 11:48 AM	#4
bigmac73 Senior Member Join Date: Mar 2012 Location: Chesapeake, Va Posts: 1,275	Re: Highest ratio gears usable?? is a 3:55 available for the 12 bolt? it is a good ratio __________________ Mike 72 C-10 Cheyenne off frame resto and Upgraded to 4 wheel disk, Tilt, Dakota Digital Dash / Rear slider. 421 SBC / TH350 3000RPM Stall Progression Ignition /Holley 750 DP/3:73 gear Eaton Limited Slip unit / 2 1/2 exhaust glasspacks

10-03-2016, 03:25 PM	#6
Mrturner1 Registered User Join Date: Nov 2015 Location: Colfax California Posts: 1,644	Re: Highest ratio gears usable?? 4.56's with a Gear Vendors over/underdrive, perfect lol

10-03-2016, 03:54 PM	#7
truckster Senior Member Join Date: Jan 2001 Location: Orem, Utah Posts: 7,976	Re: Highest ratio gears usable?? You don't mention your tire size. That's a critical component in determining what your final drive ratio will be.

10-03-2016, 04:20 PM	#8
71meangreenc10 Its a Truck Thing...... Join Date: Dec 2004 Location: Sierra Vista, Arizona Posts: 3,179	Re: Highest ratio gears usable?? I put 3.42's in mine and with OD it works well on the interstate. If you have 4.11's now, you will have to change your carrier to a 3 series carrier. Someone else can chime in on that one... Smitty __________________ 71 C10 283/3SPD Full Resto 71 GMC 1500 Sierra Grande http://67-72chevytrucks.com/vboard/s...d.php?t=518599 70 C10 Suburban Former military GSA truck. 72 Chevy Blazer 4X4, Sloppy Jo, Mountain Climber. Wife says no more trucks. http://67-72chevytrucks.com/vboard/s...d.php?t=707378 72 GMC 1 Ton Motor Home, wife said no more trucks until she saw this one. Gen 3 6.0/4L80E 4.10 http://67-72chevytrucks.com/vboard/s...d.php?t=761110 68 GMC Suburban was 3/4 ton, now 1/2.Wife shook her head 71 C30 Wrecker 71 C20 Scott-Bilt As weird as it gets..BB Cheyenne AC Truck 68 GMC Long Stepside. They keep following me home 69 C30 Former Motor Home, Flat Bed time 70 G20 Red-E-Kamp Conversion "I'm your Boogy Van"

10-05-2016, 11:58 AM	#11
Bigdav160 Registered User Join Date: Apr 2011 Location: Klein Texas Posts: 3,852	Re: Highest ratio gears usable?? Because as the pinion gear gets smaller the ring gear mounting on the differential case has to move over. Attached Images __________________ My Classics: '72 K20 Suburban + '65 Dodge Town Wagon '72 Corvette Roadster +'67 Corvette Roadster '73 Z-28 Camaro '63 Ford SWB Uni Pickup '50 Ford Coupe

10-05-2016, 12:01 PM	#12
AnotherWs6 Registered User Join Date: Feb 2016 Location: Westchester, NY Posts: 602	Re: Highest ratio gears usable?? Tire size is important, agreed. What do you have OP? Think I've got a 235/70/15 along with 3.08's. Allows me to cruise at 70mph no problem. __________________ 1968 C-10 Suburban - Original 396/TH400 2002 Transam WS6 - M6 - Black/Black - Evil Garage Queen 2000 Silverado - DD - Small lift+Body lift+35" Duratracs+4.88's + Eaton TruTrac - Monster Truck 2010 Cadillac CTS Wagon Sport - Wife's DD and the only classy car we have.



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