Factory "limited slip"locker" in 67-72 K20 front axle?? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

69oldie · 03-04-2003, 09:06 PM

What years was this an option for in the K20? What type of traction assist was it...........detroit, limited slip,...etc? What was listed on the glove box door for this option??
Just want to know because up until now, I didn't think this existed???? Is this a rare option??
Thanks
Jim

mikep · 03-04-2003, 09:17 PM

I dont know how rare of an option it is but I can say I know its not a terribly good idea to have a locker in the front. Makes for a miserable driving experience on paved roads. Its not bad on dirt for a special purpose vehicle. Clutch poitractions on the road are also creepy to drive. They pull hard to center although they dont transfer all the ratcheting to the center like front lockers do . I have had a few friends with front lockers and clutched posis over the years that they added themselves. I cant say I would do the same unless I was doing a lot of off road stuff. Otherwise its a big hassle.

**jerry moss** · 03-04-2003, 09:53 PM

glovebox door option # 9501AA

Rod · 03-04-2003, 10:27 PM

This option sheet was posted about day ago...note the front posi option...although this is a Blazer option sheet.

1969 GMC · 03-04-2003, 10:55 PM

well, if it has a "posi" front end, then it has a limited slip of some kind, I don't think it would have a locker.

O'l Buck · 03-05-2003, 03:23 AM

my dad's got a 67 K-20 that the option sticker lists "no spin" differentials......I'm not sure what kind of locker they have, but nothing gives anywhere.....they act like the spiders are welded solid. It drives like a hog, turns super hard, hops around corners, and is nearly impossible to turn in the mud, but it will go about anywhere......I've only seen it stuck once in the 25 years he's owned it......and that was when he dropped it to the frame on one side in a chisel track while feeding cows.......it couldn't climb out because we couldn't pull on the steering wheel hard enough to get a bite on the rut.........Tractor couldn't get it out either. It sat there for 2 weeks till the ground got dry enough to drive it out.

Dean · 03-05-2003, 08:29 AM

One of my 71 K20s has the posi front end. It is listed on the glove box. I have had the front end apart and it is a posi, not a locker like the rear has in it. The front end cover also has a posi tag on one of the bolt holes. This truck is a little strange because someone ordered all the creature comforts (air, cheyenne, tilt, am/fm, etc) plus 4.56 gears, locker and posi front. And the best part was the guy I bought it from had no idea. I started the body off restoration on this particular truck in Jan.

I would never recommend locking the hubs in unless you were on a semi slick surface. It puts everything in a bind on a surface with lots of traction. I have lockers in the rear of all my K20s but this is the only posi front I have seen around here.

smokekiki · 03-05-2003, 10:31 AM

My blazer has a posi in the front.As long as the hubs are not locked in, and transfer case is in 2 wheel, the front axel is not driven.When locked in you should be on wet snowy roads or off road where the tires have some slippage.

smithjp1 · 03-05-2003, 08:30 PM

I have both front and rear axle options on mine

79510AA Positract RR Axle
79501BB Positract Frt Axle

options on my Glove Box

ozarkhippie · 03-05-2003, 09:14 PM

I was wondering on one with a posi or limited slip in the front if you can lock in only one lockout if it would turn better in the mud?

mikep684x4 · 03-06-2003, 01:11 AM

My 71 lgbd has locker in the rear and posi in the front.All stock from what I can tell.

O'l Buck · 03-06-2003, 02:11 AM

we have discovered that you can turn the truck better if you lock only 1 hub, but I wouldn't recommend it because it's pretty hard on the axle that is driving, and depending on what style locker it has, it can be fatal for a differential.

03-04-2003, 09:06 PM	#1
69oldie Never too many LONGHORNS! Join Date: Dec 1999 Location: Los Angeles Calififornia Posts: 423	Factory "limited slip"locker" in 67-72 K20 front axle?? What years was this an option for in the K20? What type of traction assist was it...........detroit, limited slip,...etc? What was listed on the glove box door for this option?? Just want to know because up until now, I didn't think this existed???? Is this a rare option?? Thanks Jim

03-04-2003, 09:17 PM	#2
mikep Used to have a truck Join Date: May 2002 Location: port orchard WA Posts: 1,552	I dont know how rare of an option it is but I can say I know its not a terribly good idea to have a locker in the front. Makes for a miserable driving experience on paved roads. Its not bad on dirt for a special purpose vehicle. Clutch poitractions on the road are also creepy to drive. They pull hard to center although they dont transfer all the ratcheting to the center like front lockers do . I have had a few friends with front lockers and clutched posis over the years that they added themselves. I cant say I would do the same unless I was doing a lot of off road stuff. Otherwise its a big hassle. __________________ No truck :-(

03-04-2003, 09:53 PM	#3
jerry moss Born Psycho Join Date: Feb 2001 Location: brentwood,cal,usa Posts: 4,815	glovebox door option # 9501AA __________________ jerry moss 72 cheyenne super K20- tilt,tach,vacuum,speedwarning,buckets,shoulder belts,am/fm,tow hooks,bumper guards,toolbox,aux. fuel tank,posi front and rear,plus other goodies!!! SOLD 69 suburban K20-tilt,tach,vacuum,speedwarning,buckets,shoulder belts,am/fm,4 inch all spring lift,4 speed, 14 bolt full floater, dana 44 HD,warn winch,posi front and rear,tow hooks,plus other goodies. 73/80 chevy/gmc K20 SB400,turbo 400,205,tilt,a-c,gas hog. 77 K/5 cheyenne blazer-daily driver/beater. SON HAS IT NOW BRENTWOOD,CALIFORNIA

03-04-2003, 10:27 PM	#4
Rod Join Date: Dec 1999 Location: Eastern - Manitoba Canada, Winnipeg Posts: 4,369	This option sheet was posted about day ago...note the front posi option...although this is a Blazer option sheet. Attached Images __________________ Senior active founding member. 70 3/4 ton GMC Suburban 4x4 250/4 spd. 71 1/2 ton Suburban Chevy 4x4, 350/350 72 Chev 1 ton tow truck 402BB w/Holmes 440 wrecker on propane 2005 FLSTSCI Harley Springer 85 FXSB Harley Lowrider 72 Triumph 650 Bonneville 5spd "Poor people don't have hobbies" Quote from wife.

03-04-2003, 10:55 PM	#5
1969 GMC Registered User Join Date: Feb 2003 Location: The Rubber City Posts: 5,498	well, if it has a "posi" front end, then it has a limited slip of some kind, I don't think it would have a locker. __________________ 1969 GMC K2500 1996 Honda Accord 2007 Kawasaki KLR 650

03-05-2003, 03:23 AM	#6
O'l Buck Recovering Truck Driver Join Date: Mar 2002 Location: Orleans, NE USA Posts: 1,883	my dad's got a 67 K-20 that the option sticker lists "no spin" differentials......I'm not sure what kind of locker they have, but nothing gives anywhere.....they act like the spiders are welded solid. It drives like a hog, turns super hard, hops around corners, and is nearly impossible to turn in the mud, but it will go about anywhere......I've only seen it stuck once in the 25 years he's owned it......and that was when he dropped it to the frame on one side in a chisel track while feeding cows.......it couldn't climb out because we couldn't pull on the steering wheel hard enough to get a bite on the rut.........Tractor couldn't get it out either. It sat there for 2 weeks till the ground got dry enough to drive it out. __________________ 67 K-20 350, SM465, Eaton rear, 4.56 no spin option 00 Dodge 2500 4x4, 24V cummins, 5 speed Chad South Central Nebraska

03-05-2003, 08:29 AM	#7
Dean Senior Member Join Date: Jan 2000 Location: Cincinnati, Ohio Posts: 1,492	One of my 71 K20s has the posi front end. It is listed on the glove box. I have had the front end apart and it is a posi, not a locker like the rear has in it. The front end cover also has a posi tag on one of the bolt holes. This truck is a little strange because someone ordered all the creature comforts (air, cheyenne, tilt, am/fm, etc) plus 4.56 gears, locker and posi front. And the best part was the guy I bought it from had no idea. I started the body off restoration on this particular truck in Jan. I would never recommend locking the hubs in unless you were on a semi slick surface. It puts everything in a bind on a surface with lots of traction. I have lockers in the rear of all my K20s but this is the only posi front I have seen around here.

03-05-2003, 10:31 AM	#8
smokekiki Mike Join Date: Jan 2003 Location: west chester pa Posts: 2,474	My blazer has a posi in the front.As long as the hubs are not locked in, and transfer case is in 2 wheel, the front axel is not driven.When locked in you should be on wet snowy roads or off road where the tires have some slippage. __________________ 70'c/10, 71 suburban4x4 402bb, 72suburban 4/6 drop, 72k/5 4x4 blazer 4" lift 35 tires

03-05-2003, 08:30 PM	#9
smithjp1 Registered User Join Date: Dec 2002 Location: Katy, Texas Posts: 116	I have both front and rear axle options on mine 79510AA Positract RR Axle 79501BB Positract Frt Axle options on my Glove Box __________________ 1968 4x4 swb

03-05-2003, 09:14 PM	#10
ozarkhippie Registered User Join Date: Nov 2002 Location: Eureka Springs AR Posts: 494	I was wondering on one with a posi or limited slip in the front if you can lock in only one lockout if it would turn better in the mud? __________________ Buy Sale or Trade 71 3/4 4x4 72 1/2 ton cheyenne 4x4

03-06-2003, 01:11 AM	#11
mikep684x4 Seeker of the big and bad Join Date: Nov 2000 Location: wheatland,Calif,yuba Posts: 105	My 71 lgbd has locker in the rear and posi in the front.All stock from what I can tell. __________________ 71 3/4 ton 4x4,665hp 454. 67 GMC 1 ton towtruck 68 chevy LB 4x4 64 chevy LB custom 57 Bel-air 2d station wagon

03-06-2003, 02:11 AM	#12
O'l Buck Recovering Truck Driver Join Date: Mar 2002 Location: Orleans, NE USA Posts: 1,883	we have discovered that you can turn the truck better if you lock only 1 hub, but I wouldn't recommend it because it's pretty hard on the axle that is driving, and depending on what style locker it has, it can be fatal for a differential. __________________ 67 K-20 350, SM465, Eaton rear, 4.56 no spin option 00 Dodge 2500 4x4, 24V cummins, 5 speed Chad South Central Nebraska



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