71 k20 questions on gears and etc.. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

409impala1 · 05-22-2010, 11:05 PM

how rare was the option for a wood floor?

what gears would have been available for a 350 - 4 speed- 3/4 ton 4x4?
my spid does not tell what ratio it has. I am just lazy and did not want to take the cover off the diff.

what posi units will work in this?

Are the axles floaters?

why did they not put the 402 in a 4x4???

Shyguy · 05-23-2010, 11:46 AM

All good questions, but unfortunately I have no answers.

This will take it to the top and hopefully someone else will chime in.

Danny

martindc1 · 05-23-2010, 01:47 PM

If it has the big hubs sticking out in the rear then its a full floater. Look at the axle and see if the center section is removable from the front of the housing or not. I'm guessing its either a 4.11 or a 4.57. You can lift up the rearend and in neutral turn the tire one time while counting how many times the drive shaft turns to figure out the gearing. But you will have to find out what rear axle it has before determining what differential you could put in it.

raycow · 05-30-2010, 02:36 AM

Quote:

Originally Posted by 409impala1

my spid does not tell what ratio it has. I am just lazy and did not want to take the cover off the diff.

You can count the ratio directly without taking off the cover.

Put matching marks on the pinion yoke and differential housing. Jack one rear wheel off the ground, put the transmission in neutral, and the parking brake off. Turn the wheel exactly TWO revolutions and count how many times the driveshaft turns, estimating any fractional turn as closely as possible. That number is your axle ratio.

Ray

Hammer500 · 05-30-2010, 02:42 AM

you may want to check your front diff cover bolts and see if the tag is still attached that has the ratio stamped on it.

409impala1 · 06-04-2010, 09:18 AM

ttt

**special-K** · 06-04-2010, 09:37 AM

The 402 was too tight a fit.No real demand.350/250hp was considered plenty of power for a low geared truck that a 6 cyl could push.

You should have the HO52 rear which would have been a 4.11 or 4.57.I seriously doubt it would be the 5.13.All 8-lug axles were full-floating back then.

The Detroit Locker was available for these rears.Not any longer.GM offered this as the No-Spin.You can use a 14-bolt traction device with 14-bolt axles.It`s not too bad,but not bolt-in.

The woodfloor option was not real common,but not all that rare.I`m sure the dealers went with a steel floor and only spec`d out trucks got the option.It was the latest greatest thing to have a steel floor in`67.

**CPNE** · 06-04-2010, 12:22 PM

If the drivetrain combo you described is original to the truck and the glove box spid is original too, then I can guarantee you it left the factory with 4:11 gears. Of course anything could have been changed in 40 years

05-22-2010, 11:05 PM	#1
409impala1 Registered User Join Date: Dec 2005 Location: nebraska Posts: 136	71 k20 questions on gears and etc.. how rare was the option for a wood floor? what gears would have been available for a 350 - 4 speed- 3/4 ton 4x4? my spid does not tell what ratio it has. I am just lazy and did not want to take the cover off the diff. what posi units will work in this? Are the axles floaters? why did they not put the 402 in a 4x4???

05-23-2010, 11:46 AM	#2
Shyguy Junior Member Join Date: Dec 2006 Location: Southeast Missouri Posts: 2,436	Re: 71 k20 questions on gears and etc.. All good questions, but unfortunately I have no answers. This will take it to the top and hopefully someone else will chime in. Danny __________________ '67 Chevy C-20 short stepper - build complete, 454/SM-465. '75 C-30 Single Cab DRW-350 small block/NP-435. '77 GMC-6500 Dump Truck, 427 Tall Deck. '92 GMC K-3500 Duallie, 454/4L80E.

05-23-2010, 01:47 PM	#3
martindc1 Registered User Join Date: Jul 2009 Location: La Crosse, WI Posts: 218	Re: 71 k20 questions on gears and etc.. If it has the big hubs sticking out in the rear then its a full floater. Look at the axle and see if the center section is removable from the front of the housing or not. I'm guessing its either a 4.11 or a 4.57. You can lift up the rearend and in neutral turn the tire one time while counting how many times the drive shaft turns to figure out the gearing. But you will have to find out what rear axle it has before determining what differential you could put in it. __________________ Currently truckless, previous trucks: 67 K20, 87 K10 aka V10 & 72 C10

05-30-2010, 02:42 AM	#5
Hammer500 Registered User Join Date: May 2009 Location: Calgary, Alberta Posts: 115	Re: 71 k20 questions on gears and etc.. you may want to check your front diff cover bolts and see if the tag is still attached that has the ratio stamped on it. __________________ 69 Chev C/10 350/200 4R LWB 69 Chev K/20 4x4 350/4sp LWB 69 GMC Sierra Grande 396/400 LWB

06-04-2010, 09:18 AM	#6
409impala1 Registered User Join Date: Dec 2005 Location: nebraska Posts: 136	Re: 71 k20 questions on gears and etc.. ttt

06-04-2010, 09:37 AM	#7
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,858	Re: 71 k20 questions on gears and etc.. The 402 was too tight a fit.No real demand.350/250hp was considered plenty of power for a low geared truck that a 6 cyl could push. You should have the HO52 rear which would have been a 4.11 or 4.57.I seriously doubt it would be the 5.13.All 8-lug axles were full-floating back then. The Detroit Locker was available for these rears.Not any longer.GM offered this as the No-Spin.You can use a 14-bolt traction device with 14-bolt axles.It`s not too bad,but not bolt-in. The woodfloor option was not real common,but not all that rare.I`m sure the dealers went with a steel floor and only spec`d out trucks got the option.It was the latest greatest thing to have a steel floor in`67. __________________ "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 ~

06-04-2010, 12:22 PM	#8
CPNE Resident Curmudgeon Join Date: Dec 1999 Location: NH Posts: 6,664	Re: 71 k20 questions on gears and etc.. If the drivetrain combo you described is original to the truck and the glove box spid is original too, then I can guarantee you it left the factory with 4:11 gears. Of course anything could have been changed in 40 years __________________ Currently on or near the homestead: 67 Chevy SWB 2WD stepside 350/3 on tree (Pat's) 67 GMC SWB 2WD Fleet 402/auto (Brian's under construction) 67 Chevy 3/4 ton 2WD 402/auto (Business Hauler) 67 Chevy 1 ton dually 2WD 396/4 speed (Former business hauler, Needs TLC) 68 Chevy 1/2 ton Suburban 2WD 250 six/3 on tree (Brian's Needs TLC) 70 Chevy 3/4 ton 4WD 350/4 speed (Pat's - Disguised as a 68 GMC) 71 Chevy SWB stepside (Crushed by tree - parts donor) 72 Chevy 3/4 ton 4WD (Parts donor) 72 Chevy 3/4 ton 4WD Suburban (Parts Donor) 72 GMC 3/4 ton 4WD 292 six/4 speed (Mine - Disguised as a 67 GMC) 81 GMC 4WD Dually Dump Body 350/4 speed (Business Hauler) 82 Camaro Z/28 355/Super T-10 (Pat's toy) 93 Caprice 9C1 (Brian's Cop Car) 02 Toyota Camry (Reliable but a souless steel and plastic hulk) 2011 2SS RS Camaro M6 Factory Hurst Shifter Maybe I need to sell some of this crap Yet another Bozo with a sawz-all



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