Author Topic: New to GM 4WD Pickups: The Good and the Bad  (Read 2892 times)

Offline roo_ster

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New to GM 4WD Pickups: The Good and the Bad
« on: February 18, 2021, 03:11:15 PM »
Howdy:

Is there any GM 4WD gear/configurations best avoided?  Any that is preferred?

I am on the prowl for a 4WD GM pickup, Blazer, or Suburban, 1973-2006, preferably 1973-1987 (or 1991 for Subs). I have some time behind the wheel and under GM pickups, but precious little with GM 4WD.  My 4WD experience was with HMMWV and RSOV in the service.  Those are entirely different critters.

Offline JohnnyPopper

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Re: New to GM 4WD Pickups: The Good and the Bad
« Reply #1 on: February 18, 2021, 04:15:43 PM »
Avoid the NP203 full time Transfer case. I think they stopped making/using them in 1979.

They are convertible to part time if you get stuck with one.

I'd look for a NP205.
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

Offline blazer74

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Re: New to GM 4WD Pickups: The Good and the Bad
« Reply #2 on: February 19, 2021, 03:10:19 PM »
Might want to reference your intentions with the truck.

Offline roo_ster

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Re: New to GM 4WD Pickups: The Good and the Bad
« Reply #3 on: February 19, 2021, 07:22:59 PM »
Avoid the NP203 full time Transfer case. I think they stopped making/using them in 1979.

They are convertible to part time if you get stuck with one.

I'd look for a NP205.

Thanks for the heads-up.

Might want to reference your intentions with the truck.

4WD truck stuff.  Like the 2WD trucks I have owned, but with more off-road/bad-road and snow capability.

Am I missing something?

Offline bd

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Re: New to GM 4WD Pickups: The Good and the Bad
« Reply #4 on: February 19, 2021, 07:34:40 PM »
Might want to reference your intentions with the truck.

4WD truck stuff.  Like the 2WD trucks I have owned, but with more off-road/bad-road and snow capability.

Am I missing something?

Daily driver, work truck, rock crawling, mudding, overland, expeditions, hunting/fishing, graded forest service roads, highway, mall queen, etc...
Rich
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In other words... if people learn by making mistakes, by now I should know just about everything!!!
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Offline roo_ster

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Re: New to GM 4WD Pickups: The Good and the Bad
« Reply #5 on: February 19, 2021, 07:39:55 PM »
Might want to reference your intentions with the truck.

4WD truck stuff.  Like the 2WD trucks I have owned, but with more off-road/bad-road and snow capability.

Am I missing something?

Daily driver, work truck, rock crawling, mudding, overland, expeditions, hunting/fishing, graded forest service roads, highway, mall queen, etc...

Oh, I see. 

Daily driver I can toss gear in the back and take hunting.  Not looking to 4WD as the end, but as the means to get other things done.

Offline JohnnyPopper

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Re: New to GM 4WD Pickups: The Good and the Bad
« Reply #6 on: February 19, 2021, 08:02:38 PM »
Or just looking nature over...but hey!

You really don't need a truck for that but it helps  ::)
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

Offline 75gmck25

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Re: New to GM 4WD Pickups: The Good and the Bad
« Reply #7 on: March 04, 2021, 06:28:05 PM »
The NP203 Full-time 4WD transfer case was used by all three US manufacturers in various models during the 70's .  The NP203 is chain-driven, which is less durable than the gear driven NP205, but it seems to be stronger than the later NP208 chain-driven transfer case.

Full time 4WD seemed like a good idea because the NP203 also has a differential in the transfer case that allows you to go both on and off road without any binding of the drivetrain.  You just leave it in the High position. Whenever you need traditional 4WD you just move the shifter to one of the Loc positions and you have regular 4WD high or low.   It was a very early version of All Wheel Drive, with the option to quickly shift into traditional 4WD whenever you needed it.

However, the NP203 got a reputation for horrible gas mileage because it was used during the early emissions period when none of the manufacturers knew how to lower emissions without screwing up horsepower and gas mileage.   Those were the days of SBC 350's rated at 175 HP.  Milemarker and other manufacturers developed a part-time conversion kit that could be used to convert it to part-time operation.  There was a cheap conversion kit that only changed a few internal pawls, and a more expensive/stronger conversion kit that replaced the entire shaft inside the case.  The cheaper kit usually works fine, but may break if abused, and the stronger kit is no longer manufactured.

Bottom line - you probably want to look for a truck with something other than the NP203, but keep the big picture in mind.  If  your potential "off-road truck" gets a couple miles per gallon less because it has an unconverted NP203, is that really enough to make you not buy it?

Bruce

Offline Mike81K10

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Re: New to GM 4WD Pickups: The Good and the Bad
« Reply #8 on: March 04, 2021, 07:35:09 PM »
My NP205 in my 81 4x4 (manual locking hubs) has taken some heavy loads of wood, pulling a boat cross country, 4x4 off road in woods for deer hunting, rough mountain trail driving, steep and rocky mountain trails, snow, mud, and has never let me down (never had a break down - pulled others that was stranded). Of course my truck has always got TLC with regular maintenance. Love my truck and is why I am doing a complete rebuild.
« Last Edit: March 04, 2021, 07:38:35 PM by Mike81K10 »
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Offline 75gmck25

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Re: New to GM 4WD Pickups: The Good and the Bad
« Reply #9 on: March 05, 2021, 10:37:52 AM »
I have a stock NP203 in my '75 K25 and it has held up well over the years as a farm truck and for construction hauling.   

And despite all the discussions I've read about the NP203 and its merits, I have never run across one where someone was complaining that it had actually broken and left them stranded.  Even the old ones with a stretched chain just seem to get noisier.

Bruce


Offline Mike81K10

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Re: New to GM 4WD Pickups: The Good and the Bad
« Reply #10 on: March 05, 2021, 11:19:40 AM »
The most important thing is preventive maintenance and if it is abused or not, what ever you have. I would not focus on the transfer case when buying an old square, just condition and price.
"Tell me and I forget. Teach me and I remember. Involve me and I learn." -Benjamin Franklin

Offline frotosride

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Re: New to GM 4WD Pickups: The Good and the Bad
« Reply #11 on: March 08, 2021, 12:00:04 AM »
Avoid the NP203 full time Transfer case. I think they stopped making/using them in 1979.

They are convertible to part time if you get stuck with one.

I'd look for a NP205.

I second or third or wherever I fall on this motion. I know they are capable transfer cases but the problems I have with them are simply 2.
First and foremost is its dang size...crying out loud....that's what you will be doing when you have to take one out by yourself.
Secondly, to go with that is the cost of a full rebuild, one you can be proud of...yikes!

I also second this...
The most important thing is preventive maintenance and if it is abused or not, what ever you have. I would not focus on the transfer case when buying an old square, just condition and price.

Test drive whatever you find. Put in 4high and low, lock the hubs and make sure it moves properly within your mechanical and bargaining abilities.
Lastly check the frame throughly. Especially where the steering box bolts on. Cracks aren't a nogo for some..refer to my previous statement...within your mechanical and bargaining abilities.
« Last Edit: March 08, 2021, 12:04:12 AM by frotosride »
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