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Old 05-28-2017, 12:07 PM   #1
'63GENIII
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1976 K20 - Factory front Posi?

Hey all,

Tried searching this and Im also in a bit of a rush. Im looking into finding another front axle (Dana 44) for the '63 as I just found out yesterday while tearing it apart that one of my knuckles is hosed beyond repair.

I found an axle on CL thats 2 hours away which I can get on my day off tomorrow. Its out of a '76 K20 thats being parted. Same ratio, hub locks, rotors etc. The thing thats throwing me off though (and it's not a deal killer either) is that the guy is saying its a factory POSI front axle. He says its stated on the SPID sheet in the glove box.

I know I live under a rock, but was factory front POSI available or common from the factory in the square body trucks back then?

Any info is appreciated! Gonna try to get out there tomorrow to grab this thing.
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Old 05-28-2017, 12:42 PM   #2
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Re: 1976 K20 - Factory front Posi?

I can't answer yes or no on whether it was available from the factory, but it would NOT be in an original automatic-equipped truck that came without locking front hubs. From what I've seen, automatic trucks always had fully-engaged front hubs--they'd make short work of a posi unit up front.
Now, if it was a manual trans, with manually-locking hubs, there's no reason it couldn't have a posi unit it in, as driving down the road with the front hubs disengaged wouldn't be spinning the posi unit and wearing out the clutches in turns and corners.

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Old 05-28-2017, 01:48 PM   #3
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Re: 1976 K20 - Factory front Posi?

Good point there Brad. It is an auto. Don't know what t case though. The guy Im talking to about the axle is asking pretty good money for it and can't even say whether it's in good shape or not. IDK. Maybe I just keep looking.

Thanks for the reply. Good info!
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Vortec 7.4 - L29 Blackbear tune, Five 0 Motorsports injectors, Chris Straub Cam, NV4500, divorced 205
52" front and 63" rear spring swap
D44 / 14bff - disc axles
Milemarker 9K and 10.5K hydraulic winches

63" & B52 Spring Install http://67-72chevytrucks.com/vboard/s...ng+swap+thread


NV4500 Reverse Build Thread http://67-72chevytrucks.com/vboard/s...=reverse+build

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Old 05-28-2017, 04:28 PM   #4
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Re: 1976 K20 - Factory front Posi?

Don't walk away from it yet: If it's an auto, but it has locking hubs, it could be a posi. I don't know if manually locking hubs were an option of automatci-equipped trucks: I just know that every time I've run across an automatic 4x4 in the junkyard from that era--be it Chevy or Dodge-- they all have fixed hubs with no manual locks.

It's very possible someone might have added locking hubs to that truck, and then added a posi-unit, too. Ask for pics of the hubs, and when you get there pull the cover to see if it's a posi unit. (or just spin one tire and hold the other, with the hubs engaged. If they both spin, it's posi, if you can stop one, it's not)

-Brad
(on a side note, I enjoy every post you've made about your truck!)
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Old 05-28-2017, 06:22 PM   #5
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Re: 1976 K20 - Factory front Posi?

I don't know what years did what, but at some point an automatic with locking hubs became an option along side of the full-time option. These would have NP205s. It seems all '76s were full-time, but could be wrong. I know in '79 they could be had part-time auto for sure. Then on posi front, I don't know about in '76 but I know i the 69-72 era it was offered. I wonder if this guy is getting posi and full-time mixed up. The term "Loc" is used for shifting the NP203
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Old 05-28-2017, 09:56 PM   #6
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Re: 1976 K20 - Factory front Posi?

I have no idea what an automatic trans and locking hubs have to do with each other. For a few years in the mid-late 70s full time 4 wheel drive was used, which was universally hated. Those trucks had no locking hubs but were often converted because the trucks used gas and ate front driveshafts.
Limited slip in front is a bit rare since it tends to make the truck happily drive into the ditch w/ an inexperienced driver. Fun though.
I'd ask for a pic of the evidence and the locking hubs. I'f the seller will pull the cover, a pic of the posi, and/or the tag on the cover.
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Old 05-28-2017, 11:27 PM   #7
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Re: 1976 K20 - Factory front Posi?

DeadheadNM has a '72 K5 with a factory LSD listed on the spid (IIRC)
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Old 05-29-2017, 12:38 AM   #8
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Re: 1976 K20 - Factory front Posi?

Depending what he's asking - pick n pull has a half off sale this weekend, might be worth picking up a front end and swapping gears if they aren't the same ratio.
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Old 05-29-2017, 11:44 AM   #9
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Re: 1976 K20 - Factory front Posi?

Quote:
Originally Posted by Brad54 View Post
Don't walk away from it yet: If it's an auto, but it has locking hubs, it could be a posi. I don't know if manually locking hubs were an option of automatci-equipped trucks: I just know that every time I've run across an automatic 4x4 in the junkyard from that era--be it Chevy or Dodge-- they all have fixed hubs with no manual locks.



It's very possible someone might have added locking hubs to that truck, and then added a posi-unit, too. Ask for pics of the hubs, and when you get there pull the cover to see if it's a posi unit. (or just spin one tire and hold the other, with the hubs engaged. If they both spin, it's posi, if you can stop one, it's not)

-Brad
(on a side note, I enjoy every post you've made about your truck!)
Thanks for the kind words. I think I got a little frustrated with the guy's "I know what this stuff is worth" attitude. For the money that he wanted, Id be well on my way to a D60. I figured that he might have been a younger kid trying to sell the stuff.

Quote:
Originally Posted by special-K View Post
I don't know what years did what, but at some point an automatic with locking hubs became an option along side of the full-time option. These would have NP205s. It seems all '76s were full-time, but could be wrong. I know in '79 they could be had part-time auto for sure. Then on posi front, I don't know about in '76 but I know i the 69-72 era it was offered. I wonder if this guy is getting posi and full-time mixed up. The term "Loc" is used for shifting the NP203
Quote:
Originally Posted by B. W. View Post
DeadheadNM has a '72 K5 with a factory LSD listed on the spid (IIRC)
Hmmm. Interesting. Just never seen a factory LSD. Although I do like the idea of a traction aid in front, Im more inclined to look towards a selectable type like ARB or OX Locker.

The Posi was just was too tempting to pass up. Couldn't deal with the guy's attitude though.

Quote:
Originally Posted by nonstop View Post
Depending what he's asking - pick n pull has a half off sale this weekend, might be worth picking up a front end and swapping gears if they aren't the same ratio.
There's a thought! wonder if the have any Chevy 4x4s down there.
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Vortec 7.4 - L29 Blackbear tune, Five 0 Motorsports injectors, Chris Straub Cam, NV4500, divorced 205
52" front and 63" rear spring swap
D44 / 14bff - disc axles
Milemarker 9K and 10.5K hydraulic winches

63" & B52 Spring Install http://67-72chevytrucks.com/vboard/s...ng+swap+thread


NV4500 Reverse Build Thread http://67-72chevytrucks.com/vboard/s...=reverse+build

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Old 05-30-2017, 07:18 AM   #10
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Re: 1976 K20 - Factory front Posi?

I've been hitting junkyards now for over 20 years. Many in different states, even countries, and have never seen an LSD up front. If you go on the Dana expert site they list them up to 78/79 in certain models, but pretty sure not one was a GM. I think GM phased them out after the new models in 73, but vaguely remember seeing some in the expert. I'm gonna put one in my crew if if I ever SAS it, we'll see how it does.....
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Old 05-30-2017, 09:51 AM   #11
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Re: 1976 K20 - Factory front Posi?

No; no factory front posi on these trucks.

https://www.gmheritagecenter.com/doc...olet-Truck.pdf

RPO G80 (if that is what he is quoting) applies to the rear axle only.

K
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Old 05-30-2017, 01:21 PM   #12
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Re: 1976 K20 - Factory front Posi?

Borrowed from DeadheadNM
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Old 05-30-2017, 02:42 PM   #13
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Re: 1976 K20 - Factory front Posi?

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Originally Posted by B. W. View Post
Borrowed from DeadheadNM
7B5 looks like an SEO ("Specialty Equipment Option"), not an RPO.

Also - the SPID shown is not from a squarebody, which is what the original poster is asking about.

K
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Old 05-30-2017, 05:06 PM   #14
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Re: 1976 K20 - Factory front Posi?

You are correct on both accounts, not a regular production order but it was a factory option, SPID is from a '72 K5 as stated above.
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Old 05-31-2017, 12:45 AM   #15
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Re: 1976 K20 - Factory front Posi?

Quote:
Originally Posted by B. W. View Post
Borrowed from DeadheadNM
Aside from being a pretty well optioned truck there by the SPID, I find it a little curious that there is a POSI up front but no mention of a rear traction device? Also, what kind of intended purpose would prompt someone to order that? Plowing?

I ended up passing on that axle as the guy wanted an arm and a leg for a less than confident "It should be fine but Id go through it" evaluation. I found parts to repair mine although the Posi axle still caught my interest. I was thinking of how differently I would need to drive a Posi front axle rig on the street or highway if it ever came to it.

I still like the thought of a selectable locker in the front. Not sure Id be ok with not being able to "one leg" the front in certain situations.
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'63 k15 long step
Vortec 7.4 - L29 Blackbear tune, Five 0 Motorsports injectors, Chris Straub Cam, NV4500, divorced 205
52" front and 63" rear spring swap
D44 / 14bff - disc axles
Milemarker 9K and 10.5K hydraulic winches

63" & B52 Spring Install http://67-72chevytrucks.com/vboard/s...ng+swap+thread


NV4500 Reverse Build Thread http://67-72chevytrucks.com/vboard/s...=reverse+build

L29 - 7.4 Vortec Build http://67-72chevytrucks.com/vboard/s...&highlight=L29
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Old 05-31-2017, 07:00 AM   #16
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Re: 1976 K20 - Factory front Posi?

That SPID shws both front and rear posi. I had a short bed with both

I stated posi up front was available in the 69-72 era in my first post, just not sure about later...which is the time this thread is about. I think the seller could be confusing posi with full-time
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Old 05-31-2017, 09:07 AM   #17
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Re: 1976 K20 - Factory front Posi?

If you've got a Dana 44 up front, just start looking for a used Jeep posi unit. Depending on what gear ratio you're running up front--Jeep guys swap posi units all the time. I bought one for my Suburban's rear axle for $100 off ebay (that was several years ago, but they're still there). They usually have 3-series gears, and are looking to go 4-series.
As long as you have manual hubs up front, and disengage them, it shouldn't make a difference whether it's open or limited slip. Once you're on the trail, on gravel, sand or dirt, it should handle just fine at speeds you'd be driving.

-Brad
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Old 05-31-2017, 01:16 PM   #18
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Re: 1976 K20 - Factory front Posi?

I put a posi in my 61 dana44 closed knuckle. Chris org ft axle? whats wrong with the knuckle? Just read your other spring thread, and now know whats wrong.
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Old 05-31-2017, 01:20 PM   #19
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Re: 1976 K20 - Factory front Posi?

Quote:
Originally Posted by '63GENIII View Post
I found parts to repair mine
That's the route I would have gone anyway.
I would say swap the knuckle on yours because you know the axle, get a selectable locker if you want one. But, since you know what you did to the axle may make you want to ditch it...

Sooooo. what did you do to the knuckle? We gots ta know!
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Old 05-31-2017, 05:40 PM   #20
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Re: 1976 K20 - Factory front Posi?

it will have front disc brakes? if so your gonna havta do a disc brake redo on the master cylinder..

lots of people actually switch out the closed knuckle drum brake front end for dis set up. so finding one for your 63 ought to be easy.

network and craigs list

its a k-20?
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Old 06-01-2017, 11:11 PM   #21
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Re: 1976 K20 - Factory front Posi?

only square body that got factory posi unit was military on some of the k30 trucks if it was a service truck if i recall correctly . but it was the whimpy trac-loc NOT the good power-loc .

otherwise never seen one on civilian trucks.
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Old 10-24-2017, 06:23 PM   #22
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Re: 1976 K20 - Factory front Posi?

Not factory, but I had a 1960 frame that I installed a 1975 3/4T front axle that WAS a 3/4T, then swapped hubs with a 1/2T to get back to 6 bolt wheels, then I installed an Eaton LSD in the front.

I also had an Eaton LSD in the rear in a 1979 GM 12 bolt rear axle

I had a 350, bored 0.060", ported, polished, balanced, about 375 HP with a 4 speed.

I ran 33 x 12.50 x 15 tires with factory Rally rims.

The LSD in the rear was very nice, except with the 4 speed and bigger tires, I kept eating spiders in the rear LSD and I was in the city most of the time driving on paved roads. I would come around a corner and accelerate in an area with water from a sprinkler, catch one tire and start to spin and not get out of it soon enough and munch the rear when it got dry pavement .

The one in the front was great as long as I wasn't on a slick surface. The first time using it all locked up, I was in the mud and I discovered I could not turn a corner and about pegged a tree. Because everything was turning the same speed, I couldn't turn! I had to burp the throttle hard to get it to turn.

I typically did not drive it with the hubs locked in unless I had a good chance of getting into some bad stuff. If it was snowing, I would lock the front hubs, but run in 2WD unless I was almost stuck.

If I were to do it all over again, I would do a selectable locker in the front (ARB / Harrop) before I would do an LSD.

We are building a 1970 GMC K2500 for my son and we've installed a Detroit Locker in the rear and it behaves MUCH differently than the LSD I had in the rear of my truck from years ago. Much tighter and NO slip!
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