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post #1 of (permalink) Old 11-19-2004, 12:06 PM Thread Starter
 
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NP205 Question

I have a '78 Blazer I got about 5 months ago w/ D44 Frt and 12 Bolt rear. It has a NP205 TC behind a TH350.

My question is this (the 208 posting starting me to wonder):

My shift pattern for the T-Case in cab shows the following:

L Loc
|
L
|
N
|
H
|
H Loc

This tells me the Blazer at one point was a Full Time 4wd. There were Superwinch hubs on when I bought it and I have since replaced them with Warn Premium hubs.
Does this pattern in cab not indicate a NP203 shift Pattern? Were there NP205's that were Full Time?
The 205 seems to shift with the in cab pattern which boggles me.
Also, after coming out of 4wd and switching the hubs to Free and the TC to H, the axleshafts nor the Frt Driveshaft turn. However, go for sometime and look under the truck and now the Frt driveshaft and axleshafts are turning. What's this about considering it's supposed to be in 2wd?
Can anyone elaborate on any of the above? [img]images/graemlins/thud.gif[/img]

Thanks!
John
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post #2 of (permalink) Old 11-19-2004, 04:21 PM
K5Blazerman77
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Re: NP205 Question

the only full time 4x4 transfer case is a 203. so yours has a 4x2 conversion kit on it. as for not staying in 2 wheel hi it must be slipping because the np203 is chain driven. the kits stop the movement and cause things to not be lubed up.
post #3 of (permalink) Old 11-19-2004, 05:44 PM Thread Starter
 
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Re: NP205 Question

I went to my local 4x4 shop (Desert Rat) and spoke to someone to confirm my feelings. After investigating online the Transfer-Case is a 205. It has the PTO cover and is a cast iron case (the thickness of the 203 and 205 is noticeable from whaty I can tell.)

Anyways, the guy I ended up becoming friends with said ti was a NP205.

So, I am still somewhat stumped.

What is the shift pattern on a NP205 supposed to be?

I thought the shift pattern I laid out previously was more along the NP203 lines.

Thanks! [img]images/graemlins/chairfall.gif[/img]
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post #4 of (permalink) Old 11-19-2004, 07:28 PM
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Re: NP205 Question

look on the front of the t case above the front drive shaft there should be a tag there, u might have to scrape off some grease, but it will tell you.
post #5 of (permalink) Old 11-19-2004, 11:34 PM
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Re: NP205 Question

The shift pattern you discribed is a NP203, but it's true that it may have been swapped over to a 205. I have never owned a NP205, but I *thought* the pattern was missing one of the 203's, and I'm thinking it would be the ( L ) so it may be:

L loc
N
Hi
Hi lock

But, not ever owning one, I may be wrong on that.. I'm just trying to go on memory from over 20 years.. LOL.

As for the question about the driveshaft turning etc. I'll try to give you some idea what I think may be going on.

First off, a 203 was the only full time that GM used. When driving down the road, the front shaft would turn in a full time system. Full time system did not come with any lock outs on the hubs at all. The drive flang was simply covered by a cap.

You said you're has lock out hubs. It was pretty common for a lot of owners to switch over to lock outs, trying to get better gas mileage with a full time truck. However, there is more to the swap that just changing over the hubs. Putting lock outs on the hubs will not now make the full time system a part time system. The are also gears inside the 203 T-case that need to be changed out. Once that is all done, the system is then a part time system.

You said that the shift pattern looks like it matches the one on the floor. Either the T-case is actually a 203, or there is always the poss that I may be totally wrong about the 205 having a different pattern. The other question to be answered, would a 205 cause the front shaft to turn when in hi? I don't know for sure, but I would think not.

Your best place to start is to get under the truck and find the round metal tag on the t case, it will say if it's a 203 or a 205. From what It sounds like, it could actually be a 203. I have to assume that the guy who said it was a 205 knows what he's talking about.. but it's just not adding up to me.

Either I'm wrong about the 205's shift pattern... or you're wrong about it matching the one on the floor.. or he's wrong about it being a 205.... and if he's wrong, and it's a 203, the previous owner may not have installed the gears in the 203 to make a complete conversion.

Good luck.
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post #6 of (permalink) Old 11-20-2004, 01:30 AM
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Re: NP205 Question



There's some original GM propaganda on the operation of the NP203. Enjoy.

Tx... here's a shift knob of a 205:




As for a definite identification... crawl under the truck with a stiff plastic bristled brush. Brush all of the dirt and other grime off the front and back of the transfer case. Look for a round tag about 2" in diameter. That will have the model on it. Both the 203 and 205 are cast iron. The 203 has a gear reduction box on the front part of it. As a whole unit, the 203 is MASSIVE. The 205 is a smaller unit in comparison. THIS SITE has a few othe good key features of each t-case. There is an article concerning part time conversions HERE. Maybe reading that will help you determine if your's is setup correctly.
post #7 of (permalink) Old 11-20-2004, 09:02 PM Thread Starter
 
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Re: NP205 Question

[img]images/graemlins/goodpost.gif[/img] This is a response to both TxFireman and 83GMCK2500

Before I began this NP205 posting I intitially based my thoughts on this site - the lower picture looked more like my TC. I then saw 83GMCK2500's recommended site and it looks more like I have a NP203 possibly.

I couldn't find a 'metal tag' anywhere around the FRT driveshaft. However I did see (perhaps this is what was meant) a ground flat spot on the case itself directly above the FRT driveshatft that had the following "K8H05."

I then looked some more and found these numbers above the PTO plate "344268 GM" and I have not found a website that could decode these numbers yet (still looking. [img]images/graemlins/grin.gif[/img] )

I didn't realize the NP203 (being chain driven) had a PTO plate. I thought only the gear driven TC's would have a PTO, hence the 205. (AND DON'T MENTION ME SAYING 'I THOUGHT' AS BEING THE PROBLEM IN THE FIRST PLACE!! HAHAHAHA J/K) It's all in the learning curve I guess!! [img]images/graemlins/crybaby.gif[/img]

I would have imagined there was a conversion kit (if it is the 203 for sure) put into the TC, however I will have to open it up to verify for sure!!

Welp, I appreciate your help to this point, if someone does know what those numbers mean I would be appreciative if ya might pass it along. I know the truck originally came with a 400ci, but as far as the original tranny I am not sure (currently a TH350.)

If you all did catch me in a misguided and misinformed belief (with the wrong ID I was given @ the 4x4 shop) then as a newbie I can say I guess everyone gets one good whack to the new guy [img]images/graemlins/spank.gif[/img] !!! [img]images/graemlins/cool.gif[/img]

Thanks!
John
(I will change my profile when everything is confirmed!)
[img]images/graemlins/burnout.gif[/img]
















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post #8 of (permalink) Old 11-21-2004, 01:01 AM
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Re: NP205 Question

Prior to 1980 GM 4x4s came standard with the 205 behind manual transmissions, and the 203 behind automatics. I was reading an old brochure on GMC 4x4s (published by GM) and it stated that those were the standard configurations. We've got a '76 K15 here we're working on, it's got the 400sbc/th350/np203/d44/12bt combo.
post #9 of (permalink) Old 11-21-2004, 09:03 AM
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Re: NP205 Question

The picture of the 205 shift knob with the pattern is correct for a 205.
There is no such thing as "Lock" on a 205.
Your knob is wrong for a 205.

4 LO
N
2 HI
4 Hi

When the hubs are unlocked, AND the T-case is in 2wd, both the axles AND the t-case gears are disengaged. You can turn the front driveshaft by hand. But notice the resistance/drag - it's not super loose. The bearings and oil still exert a slight pressure - both from the lockout hubs and thwe T-case.

The reason the shaft is spinning after a high speed drive is that resistance you felt turning it also tries to make it spin while at higher speeds. The bearings and oil turn, turning the shaft. It's freewheeling, but it's not transmitting power.

If you aren't sure, tie a piece of baling wire around the shaft to something - it'll keep the shaft from turning. But when you put it in any 4x4 gear, or lock the hubs, it'll yank that wire right off.

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post #10 of (permalink) Old 11-21-2004, 09:03 AM
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Re: NP205 Question

The picture of the 205 shift knob with the pattern is correct for a 205.
There is no such thing as "Lock" on a 205.
Your knob is wrong for a 205.

4 LO
N
2 HI
4 Hi

When the hubs are unlocked, AND the T-case is in 2wd, both the axles AND the t-case gears are disengaged. You can turn the front driveshaft by hand. But notice the resistance/drag - it's not super loose. The bearings and oil still exert a slight pressure - both from the lockout hubs and thwe T-case.

The reason the shaft is spinning after a high speed drive is that resistance you felt turning it also tries to make it spin while at higher speeds. The bearings and oil turn, turning the shaft. It's freewheeling, but it's not transmitting power.

If you aren't sure, tie a piece of baling wire around the shaft to something - it'll keep the shaft from turning. But when you put it in any 4x4 gear, or lock the hubs, it'll yank that wire right off.

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