Rebuilding the 12 Bolt - What Gears do you Recommend? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

C10agent · 01-28-2014, 01:59 AM

Hey guys,
I am going to be rebuilding the 12 bolt in a couple months and I had a buddy recommend I go with 4:10 gears. I am running a 350 with vortec heads and 700r4 tranny and the 12 bolt is a single fire whiner. I want some scratch coming off the line, just don't want peg out on the highway going 70. Any thought and what are you guys running?

**leddzepp** · 01-28-2014, 02:26 AM

We need to know what size tires you are running. Generally with that engine/trans combo 3.73's are a good choice.

C10agent · 01-28-2014, 02:31 AM

I am running the Wheel Vintiques 17" Rally Wheels with 245/50/17 Generals all the way around.

THE BOSS · 01-28-2014, 06:25 AM

when I bought my 72 it had 4:88 for the dunes
I took them out and put in 3:73
if I had to do it again I would go even taller gears, low 3:00 and I have 36" tall tires. the engine runs kinda high RPM's on the highway.

now with your having a lock up converter, you might be alight with that choice. but if your going to drive on any trips, I'd go taller than 3:73

**Already Gone** · 01-28-2014, 07:23 AM

If you not going to run a mega horsepower motor and just use your truck as a cruiser with the occasional highway trip, I suggest 3:42"s will give good power and decent fuel economy.

MARKDTN · 01-28-2014, 08:37 AM

I'll second the 3.42 as a good all-around gear

C10agent · 01-28-2014, 10:22 AM

I was thinking 3.73, but this truck is literally just going to be a cruiser and not a weekend racer. Thanks for the advice!

Ridgeclimber · 01-28-2014, 10:29 AM

I have a LQ9 6 litre with a 4l60e trani. I installed a eaton posi carrier into mine. I kept the 3.73 gears just to keep the cost down. Works good. But if I was going to to it again I would of used the 3.42 gears, just because these trani's have such a low first gear.

67 chevelle · 01-28-2014, 10:34 AM

unless you are runnin a very tall tire say 35s or 38s , I would not go with 411 gears with a 700r4 , they have a very tall first gear , that works well with 308 thru 373 gears

67ChevyRedneck · 01-28-2014, 10:34 AM

Quote:

Originally Posted by C10agent

I was thinking 3.73, but this truck is literally just going to be a cruiser and not a weekend racer. Thanks for the advice!

Good choice. I've been running a 350/700R/3.73 combo since 2002. Great overall set up. Don't get super excited about high MPG. Expect 12-13 around town and 16-17mpg on the highway (70-75mph is closer to 16, 55-60mph has gotten me close to 17 a few times but it's hard to go that slow!)

C10agent · 01-28-2014, 10:49 AM

I am really glad I got y'all's advice. The buddy that is rebuilding was really pushing for them. Good to know. Thanks!

01-28-2014, 01:59 AM	#1
C10agent Registered User Join Date: Aug 2013 Location: Navasota, TX Posts: 708	Rebuilding the 12 Bolt - What Gears do you Recommend? Hey guys, I am going to be rebuilding the 12 bolt in a couple months and I had a buddy recommend I go with 4:10 gears. I am running a 350 with vortec heads and 700r4 tranny and the 12 bolt is a single fire whiner. I want some scratch coming off the line, just don't want peg out on the highway going 70. Any thought and what are you guys running?

01-28-2014, 02:26 AM	#2
leddzepp Moderator Join Date: May 2007 Location: Southern Cal Posts: 20,031	Re: Rebuilding the 12 Bolt - What Gears do you Recommend? We need to know what size tires you are running. Generally with that engine/trans combo 3.73's are a good choice. __________________ 1972 C/10 Cheyenne Super SWB. Restored, loaded, slammed. 1968 C/10 50th Anniversary LWB. Unrestored, stock, daily driver/work truck. RIP ElJay RIP 67ChevyRedneck RIP Grumpy Old Man RIP FleetsidePaul

01-28-2014, 02:31 AM	#3
C10agent Registered User Join Date: Aug 2013 Location: Navasota, TX Posts: 708	Re: Rebuilding the 12 Bolt - What Gears do you Recommend? I am running the Wheel Vintiques 17" Rally Wheels with 245/50/17 Generals all the way around.

01-28-2014, 06:25 AM	#4
THE BOSS Registered User Join Date: Jun 2012 Location: Kalamazoo MI Posts: 104	Re: Rebuilding the 12 Bolt - What Gears do you Recommend? when I bought my 72 it had 4:88 for the dunes I took them out and put in 3:73 if I had to do it again I would go even taller gears, low 3:00 and I have 36" tall tires. the engine runs kinda high RPM's on the highway. now with your having a lock up converter, you might be alight with that choice. but if your going to drive on any trips, I'd go taller than 3:73

01-28-2014, 07:23 AM	#5
Already Gone 70+ ( Old Skool Club ) Join Date: Nov 2003 Location: Saskatoon, Saskatchewan ,Canada Posts: 9,143	Re: Rebuilding the 12 Bolt - What Gears do you Recommend? If you not going to run a mega horsepower motor and just use your truck as a cruiser with the occasional highway trip, I suggest 3:42"s will give good power and decent fuel economy. __________________ 1972 C10 Custom/Deluxe 613 Highlander 406/700R4 1999 White Tahoe LS 4x2 with Z56 Police Package 1992 K1500 GMC Suburban Members I have personally met: MusicMan70 - HeavyD - ChewyChevy67 - StingRay -71SWB4x4 - 67 Burb - DeadheadNM - too much stuff - bc65 - das601 " Circumsatances Do Not Change Responsibility " " The Sky is not the Limit, Your Mind is." Marilyn Monroe .. RIP Charlie Watts 1941 - 2021

01-28-2014, 08:37 AM	#6
MARKDTN Registered User Join Date: Jan 2011 Location: Chattanooga, TN Posts: 2,165	Re: Rebuilding the 12 Bolt - What Gears do you Recommend? I'll second the 3.42 as a good all-around gear __________________ '83 K20-TPI '73 C10 '79 C10-ex-diesel(SOLD) '07 Tahoe(Son driving) '14 Suburban-DD '71 C10-current project

01-28-2014, 10:22 AM	#7
C10agent Registered User Join Date: Aug 2013 Location: Navasota, TX Posts: 708	Re: Rebuilding the 12 Bolt - What Gears do you Recommend? I was thinking 3.73, but this truck is literally just going to be a cruiser and not a weekend racer. Thanks for the advice! __________________ Neil............... 1972 C10 SWB - Shop Truck in the Works 5.3 LS / Full Air Ride / Rear Notch 20" American Racing Daytonas IG - neilioustx - pictures of build/progress Born and Raised in the Promised Land.... TEXAS Y'ALL!!

01-28-2014, 10:29 AM	#8
Ridgeclimber Registered User Join Date: Jul 2012 Location: Maple Ridge. B.C. Posts: 145	Re: Rebuilding the 12 Bolt - What Gears do you Recommend? I have a LQ9 6 litre with a 4l60e trani. I installed a eaton posi carrier into mine. I kept the 3.73 gears just to keep the cost down. Works good. But if I was going to to it again I would of used the 3.42 gears, just because these trani's have such a low first gear.

01-28-2014, 10:34 AM	#9
67 chevelle Registered User Join Date: May 2013 Location: WEST PALM FLORIDA Posts: 1,174	Re: Rebuilding the 12 Bolt - What Gears do you Recommend? unless you are runnin a very tall tire say 35s or 38s , I would not go with 411 gears with a 700r4 , they have a very tall first gear , that works well with 308 thru 373 gears __________________ 68 Long Fleet , ly6 , turbo 350 , 3-5 drop , original paint , front discs 67 Small window , 7 foot bed , tweaked 6.0 LSX 2004R Medium Olive 58 Apache fleet , 235 , offy intake , dual exhaust , 4 on the floor , red/white 69 Long Fleet , Custom , 6.0, 4l60 , AC , Medium Olive

01-28-2014, 10:49 AM	#11
C10agent Registered User Join Date: Aug 2013 Location: Navasota, TX Posts: 708	Re: Rebuilding the 12 Bolt - What Gears do you Recommend? I am really glad I got y'all's advice. The buddy that is rebuilding was really pushing for them. Good to know. Thanks! __________________ Neil............... 1972 C10 SWB - Shop Truck in the Works 5.3 LS / Full Air Ride / Rear Notch 20" American Racing Daytonas IG - neilioustx - pictures of build/progress Born and Raised in the Promised Land.... TEXAS Y'ALL!!



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