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Old 01-20-2007, 05:14 PM   #1 (permalink)
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Questions about NP203 transfer case

I have searched this entire site for the answer to my questions using the Google search method and browsing all the forums where I though the answers might be found. If my following questions are answered somewhere else on this forum, please forgive me.

I just picked up an 86 Suburban from a co-worker this weekend. It is still at his house as we need to put a motor in it so I can drive it home but I wanted to figure some things out for myself now.

He told me that the drive train under the truck is from a 74 Chevy 4WD truck and it uses an NP203 transfer case. Now for the last two days I have searched the internet for info on this particular transfer case. I know from reading that it is a full time 4WD unit but it can be converted. Now he also told me that he has installed a modified shifter that allows to shift into 2WD but still only using one stick. Is this possible?

My other question for now is I have also read about guys setting these cases up with twin sticks to make 4WD selectable and have also found a kit from Summit Racing that you install inside the case to lock the internal diff with new lockable hubs for the front axle. Has anyone done either of these conversions and how well do they work? I would also like to know if I go with the kit from Summit, why do I need new locking hubs up front?

Thanks in advance for any information. I am a rookie when it comes to 4wheelin' but have been wrenching for half my life.
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Old 01-20-2007, 05:49 PM   #2 (permalink)
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HMMM. 2wd with a different shifter, not that I know of.
Converting it is pointless to me, just double it.
Yes you can twin stick it, but that is also dumb AFAIK cause you don't get any more options.
I have a 203, I'm going to run it till I get a doubler.
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Old 01-20-2007, 05:49 PM   #3 (permalink)
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double post

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Old 01-20-2007, 06:08 PM   #4 (permalink)
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If he has installed a kit then he is more than likey put in one of the kits that you saw on summit. There is no "shifter" that converts it, what is done is the spider gears are taken out of the internal diff and replaced w/ a solid spacer that lock the two side gears. When you are in high or low the truck is in 2wd but when you put it in lock it engages the locking slider on the diff and puts it in 4wd. All the locking hubs are for is so that you can fully unlock the front axle or else the part time convertion is pretty worthless (if the 'burb already has locking hub just buy the kit that doesn't have them).
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Old 01-20-2007, 10:47 PM   #5 (permalink)
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Thanks for the replies so far.

Big One: I understand what you said that the conversion will lock the diff inside the x-fer case but if it doesn't turn the front drive shaft anymore (i.e. 4x2 operation), what is the purpose for unlocking the front hubs?
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Old 01-21-2007, 12:44 AM   #6 (permalink)
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you should always unlock your hubs when your not using the front axle
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Old 02-03-2007, 04:49 PM   #7 (permalink)
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Ok, my new toy just got a lot more complicated.

I had the trans oil pan down this morning to change a leaking gasket and found metal bits in the pan. After putting it back together and running it, it still shifts and runs but how much longer it has is anyones guess. Now to my next question....

As I stated earlier in this post I was told the drive train was out of a '74 truck with a TH350 trans, NP203 xfer case and D44/chevy 10 bolt axles. Now, if I will be needing a new trans soon, would it be better to go with the 700r4 trans and 208 transfer case that the truck originally came with or go with another option? I also wonder if my axles and driveshafts would work with that setup or do I need a whole new drive train?
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Old 02-06-2007, 03:50 PM   #8 (permalink)
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Any ideas/opinions? Anybody?
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Old 02-06-2007, 05:48 PM   #9 (permalink)
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if you could get a hold of a 700/208 combo i would use it but you will have to find a slip-yoke rear driveshaft and a longer front since the 700 is a longer trans.
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Old 02-07-2007, 02:34 PM   #10 (permalink)
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Thanks for the reply weaslzz.

At this point I am wondering if going completely back to the stock setup (trans, t-case, shafts and axles)would be a better starting point for me. I knew getting into this truck that the drivetrain was a transplant, but I didn't anticipate having problems with it so soon. I also think the stock axles are 8 lug so my rims and tires won't work.

Oh well, I guess I can just run what I have until it blows.
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Old 02-07-2007, 06:05 PM   #11 (permalink)
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if your gonna swap out trans/transfer case why use a 208? I would use a 205 for sure. up to you on a tranny 350/400/700 whatever
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Old 02-07-2007, 08:27 PM   #12 (permalink)
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Ok, now this might be a basic question but I need to ask it anyway. If I were to get my choice of tranny and a 205 t-case (I only mentioned a 208 case because that is what came stock on my truck), how could I determine if my current drive shafts would fit/bolt-up?
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Old 02-08-2007, 06:20 PM   #13 (permalink)
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tape measure?

if its still in a rig when you make a choice just measure it. its not that big of a deal though to have a drive line made shorter or longer
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Old 02-10-2007, 01:37 PM   #14 (permalink)
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uhm the 203 trucks had no hubs, they had drive flanges, they were full time 4x4 hence the name

you could not unlock the front axle lol
my 77 K-10 is 203 equipped

imho a 700r4 is not much of a good choice unless youre really bent on having OD but if you must have one then get an 87-up one
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Old 02-10-2007, 06:58 PM   #15 (permalink)
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Depends on what was meant by "little bits of metal" if they are pieces that look like broken off chunks then you have problems. If its just the metal that sticks to the magnets in the pan I wouldn't worry at all (this is normal) and I'd run it till it dies.

I only mentioned this because I actually have a buddy that gets so concerned about that dust that he gets a new car when he sees something like this and its completely normal and the reason the magnets are in the pan to begin with. I can't seem to get it through to him though:-)
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Old 02-11-2007, 03:08 PM   #16 (permalink)
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Well, for starters, I think whoever did the pan gasket last misplaced the magnet becaue there wasn't one in my pan. Yes there was some normal metal "dust" in the fluid but the part that worried me was the chunk that was about 3mm by 8mm in size. There were also a number of bits that were very small, about 2mm in size. Maybe I could just have this tranny rebuilt if/when it goes and use that time to modify my 203 to part time (or find a new one).
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Old 02-11-2007, 05:08 PM   #17 (permalink)
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the 203 is quite a bit longer than a 205, i'm not sure about a 208, but i converted a truck from a 203 to a 205 and had to have the driveline made longer, 203s are chain driven and the chain breaks or stretches sometimes, thats what happened to our truck, i would run the 205, its gear driven and alot tougher and its part time, a full time t-case is alot harder on your front axle.
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