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Author Topic: Convert back to full time  (Read 6712 times)

Offline MechanicallyIgnorant646

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Convert back to full time
« on: January 15, 2020, 11:15:55 PM »
It's a '79 GMC K1500 Sierra Grande and I'm pretty sure the hub locks on my truck are not original, and whatdayaknow, they're broken. How difficult is it to convert back to full time 4x4 and what does it involve? Thanks in advance.

I'd much prefer to not have to worry about these things breaking again.
« Last Edit: January 16, 2020, 01:41:38 AM by MechanicallyIgnorant646 »
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Offline VileZambonie

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Re: Convert back to full time
« Reply #1 on: January 16, 2020, 04:37:26 AM »
Just buy a set of quality locking hubs. They are inexpensive and easy to change. Going to full time locked hubs is not a good idea.

https://www.summitracing.com/search/part-type/locking-hubs/year/1979/make/gmc/model/k1500
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Offline MechanicallyIgnorant646

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Re: Convert back to full time
« Reply #2 on: January 16, 2020, 08:30:11 AM »
Why is it not a good idea? Seems like it would be more reliable.
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Offline zieg85

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Re: Convert back to full time
« Reply #3 on: January 16, 2020, 09:35:20 AM »
I am not sure why Vile feels that way.  Converted transfer cases need to be put in 4 wheel drive periodically for proper oiling.  The extra moving parts on a full time takes MPG down a bit and adds more wear to the moving parts. 

I agree if it is working as intended new locking hubs are much easier than convert it back.
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Offline MechanicallyIgnorant646

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Re: Convert back to full time
« Reply #4 on: January 17, 2020, 05:58:57 AM »
The extra wear, mpg and hassle of converting back makes sense.

I'm not sure but there may be, and probably is more going on here.

I got stuck a while back and front wheels were not turning. This was before the hub locks got broken.
Shop says 4x4 works just fine just use a wrench to turn them they're stiff... well they would click on the lock position just fine.. but now that I've taken their advice thinking something wasnt actually going far enough or whatever.. I broke them.. however on the lock position, can still hear a click.. and the passenger side u-joint will lock, but the passenger side u-joint doesnt, it still turns freely, and I'm betting was in that condition before I broke the hub locks in the 1st place.
So I've got at least 2 problems there to fix now.
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Offline ehjorten

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Re: Convert back to full time
« Reply #5 on: January 17, 2020, 09:04:47 AM »
Full-time 4WD is okay in these rigs, but due to the U-jointed shafts in the front, it is pretty hard on them.  You will lose a bit of MPG for what already is pretty horrible MPG compared to modern vehicles, but the biggest issue is that wear and tear on the front-end U-joints.

I have put a lot of miles on my '77 K20 with the part-time kit in the NP203 and have had zero issues.  All you need to do most days is simply pull the transfer case into 4WD for a few miles, every so often.  Sometimes I even forget and don't do it for a while.  the NP203 doesn't seem to be bothered by it.  Recently we have had some pretty good snow storms in the PNW and I have been driving this truck in snow and ice.  I just leave the hubs turned-in and when I need 4WD I just pull on the Transfer Case lever.  Almost like having Automatic 4WD! :)
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Offline JohnnyPopper

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Re: Convert back to full time
« Reply #6 on: January 17, 2020, 02:11:45 PM »
I owned my '78 for two years before I put in the part time kit and locking hubs- What a difference!!

I would not advise going back.

You must have had some cheap hub locks for them to break.

Miles Marker is what I used, they are solid.
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Offline MechanicallyIgnorant646

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Re: Convert back to full time
« Reply #7 on: January 18, 2020, 07:03:48 AM »
Quote from: JohnnyPopper on January 02, 1975, 03:13:10 PM

You must have had some cheap hub locks for them to break.


Nah, they're wern locks but I didn't buy or install them, it's just that as my handle would suggest, I know absolute jack about these things. I asked a shop to check it out because the front wheels were not spinning. I got stuck. Def had the hubs locked and tried every of the 4 options on the stick for 4x4. That cost me 100$ to get pulled out after sliding sideways off a muddy road into a ditch and watching a small suv drive right by me. Embarrassing to say the least.

So I asked the shop to check it out.. they said it works.. well no it doesnt.
When you shift the 4x4 options on the stick, you can feel it, the neutral position works truck wont move, and on one position I forget which one, a light under the dash does come on. But the front wheels still wouldn't spin like they should. I only tried driving it around the yard and short distances with them locked so maybe when I get new locks I can try again?

Shop said well we checked and it works, maybe just try turning the hub locks with a wrench or pliers theyre kinda stiff.. ok.. well my dummy self did that and busted them. They will turn full circle in one direction... and on the "lock"position, the driver side u joint will still lock, but the passenger side doesnt, still can be turned by hand.

And being completely ignorant about these things, I didn't know what to check for at that time. Beleive it or not, I was never educated about these things, didn't know what questions to ask etc...

There is no option to turn 4x4 on or off aside from the hub locks.. at least as far as I can tell. I've tried the stick in each position.

So once I get new hub locks, how can I fix the faulty u-joint?
« Last Edit: January 18, 2020, 08:25:54 AM by VileZambonie »
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Offline VileZambonie

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Re: Convert back to full time
« Reply #8 on: January 18, 2020, 08:34:10 AM »
If you are going to own one of these trucks and consider yourself mechanically ignorant, you are in for a ride. However, if you are willing to learn and do the work, you can become mechanically educated by utilizing the knowledge and resources of this forum.
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Offline MechanicallyIgnorant646

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Re: Convert back to full time
« Reply #9 on: January 18, 2020, 08:42:09 AM »
Quote from: VileZambonie on January 18, 2020, 08:34:10 AM
If you are going to own one of these trucks and consider yourself mechanically ignorant, you are in for a ride. However, if you are willing to learn and do the work, you can become mechanically educated by utilizing the knowledge and resources of this forum.

Yes sir, that's why I came here. I really need to get a service manual.

I have to admit, I'm a bit embarrassed at how little I know about vehicles in general.
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Offline VileZambonie

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Re: Convert back to full time
« Reply #10 on: January 18, 2020, 08:47:02 AM »
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74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline MechanicallyIgnorant646

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Re: Convert back to full time
« Reply #11 on: January 18, 2020, 09:15:35 AM »
Woah I wasnt looking hard enough. Thanks a bunch I appreciate the help. Def taking some time to review the manual!

Thanks again.
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Offline JohnnyPopper

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Re: Convert back to full time
« Reply #12 on: January 19, 2020, 08:11:11 PM »
Not clear on what you say about your U-joint...

One locks, but the other doesn't...

When you get your new lockers installed, put your transfer case in neutral, jack up one front wheel at a time and spin, make sure your U-joints turn behind each wheel. If one doesn't you will have to look for why it's not connecting.

Also, while your in there, it would be a good time to clean, and repack your front bearings. Looks intimidating, but as long as you have the GM locking socket you'll be fine. New seals too...

Do a search on here for the correct torque preload for the bearings.

Here's a link to the work done to convert your NP203 to part time.

https://ck5.com/forums/resources/mile-marker-np203-part-time-kit.68/

Welcome to the 'for all things square obsession site', or FATSOS!

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1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction
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