NP203 - NP205 swap questions

[45acpJr]

Ok guys I'm looking into swapping out my np203 for a np205. I have a 205 that I'm not sure if it is what I need please bear with me if I ask stupid questions I am out of my comfort area right now. This 205 came out of a truck with a th-350 (same tranny as I'm using), if has fixed yokes front and back, and has a 27 spline female input. Is this a desirable t-case for my application? Is it a direct swap? I am aware of the need for new drive shafts. Also will it bolt to my existing crossmember? The guy I bought this from took a torch to the crossmember instead of un-bolting it. I am planning on buying a rebuild kit and twin stick kit, any other suggestions?

 

[dremu]

I'm unclear on the input, as the TH350 version of the NP205 uses a male shaft, though it then has a female coupler so that may be what the guy is talking about. Lots of info on ORD's page, i.e. http://offroaddesign.com/catalog/transfercaseparts.htm

One thing you don't mention is the bolt pattern on the front of the case. You may need a different adapter from tranny to transfer case. The adapter is the cast iron "foot" at the bottom of this picture:

The picture is rotated funny, so on the left side are the two big bolts that bolt to the crossmember -- that one is for a TH350 to an NP203, on my '74. I don't know what the TH350/NP205 adapters look like.

That adapter will in turn decide what crossmember you need. Hopefully you at least get the adapter, even if the crossmember was cut up.

Another thing to check on is the size and type of the yokes. You'll need to know if you have 1310 or S44 U-joints (unless you're going big to the 1350), and note that 1310 CV's use a different size yoke than a plain 1310. (That epiphany just bit me in the butt )

If you're gonna tear the thing apart, you Might As Well® get a set of the ORD modified shift rails, so you get the full range of control (front 2WD low, etc, that you can't get with the stock setup.)

The last thing that comes to mind is that the shifters may be in a different place, so you may need to cut your floor pan up (which may be trouble if you have carpet.) Might also be worth pulling the carpet up to see if you have the removable tranny hump or if yours is welded-in.

-- A

 

[45acpJr]

I am planning on changing the yokes since I upgrade my axles to 1410s, as far as the adapter, I did get the adapter with the t-case. Should I be golden?

 

[45acpJr]

As far as the floor, I have no carpet at the moment, and it is the bolt on cover

 

[dremu]

I am planning on changing the yokes since I upgrade my axles to 1410s, as far as the adapter, I did get the adapter with the t-case. Should I be golden?

If the adapter has the same height and mounting as the one you have, then yep, it should then mount up to your existing crossmember.

Oh, and now is a good time to do poly transmission mounts. Which then means you're doing the poly motor mounts too It never ends!

When you order the rebuild kit (assuming from ORD), Stephen will need to know which yokes you're using as the output seals are sized differently. I see on their web site there's also something about bearing size, but I've not been inside an NP205, so I leave that to you and him to figure out

As far as the floor, I have no carpet at the moment, and it is the bolt on cover

Sweet. I'd remove the cover for the time you're doing the work and deal with that last. You may need to either cut yours up or go get a different one at the junkyard. At least it's easy enough to cut a new hole and weld a patch over the old one if desired.

-- A

 

[45acpJr]

Thanks for the info, I'll get under the truck and try to verify the crossmember. And as far as it never ends, trust me I know and to make it worse this is my DD so I have to plan these projects out extremely carefully.

 

[wazzabie]

Not sure what years yours is. The NP205 from a 72 K5 with a NP205-TH350 was a direct bolt in to a 78 K5 with NP203-TH30. I needed the adapter from the 72. The support strut was not on the 72 and the 78 support strut was too short. I had new drive shafts made. I did not need to cut the floor pan.

 

[45acpJr]

When you say support strut are you referring to the crossmember?

Disregard my last, I re-read it and I assume you are talking about the adapter

 

[dremu]

EDIT: Some but not all transfer cases had a "torque mount" on the side. Not all are drilled for it; they have two 9/16" holes (yes, as in 9/16" thread, giant bloody big bolts) on the passenger side. See

That's a pic from ORD's Doubler page, but at the far left of the pic you can see the two holes. Here's a pic from the GM parts book -- look above the "B":

Installed it would look like (random Google pic):

Two L-brackets, clamshells, and the rubber isolators between 'em.

-- A

 

[45acpJr]

Is that the brace that bolts to the tranny? I saw one for sale on ebay earlier

 

[dremu]

Is that the brace that bolts to the tranny? I saw one for sale on ebay earlier

Nope, that's different. Search here or Google for "transfer case brace", "brace" being different from "torque mount", apparently. See my edited post above.

-- A

 

[wazzabie]

Is that the brace that bolts to the tranny? I saw one for sale on ebay earlier

yes after 78 the brace from tcase to tranny was added. In 72 the np205 support was to the frame.

 

[diesel4me]

Not sure what years yours is. The NP205 from a 72 K5 with a NP205-TH350 was a direct bolt in to a 78 K5 with NP203-TH30. I needed the adapter from the 72. The support strut was not on the 72 and the 78 support strut was too short. I had new drive shafts made. I did not need to cut the floor pan.

That was my experience when I swapped a '72 NP-205 with a TH-350 adaptor into my '77 GMC that had a NP-203 / TH-350 setup originally...had to use the '72 NP-205 adaptor,the frame bracket & cushions for the transfer case,and the rear yoke had to be swapped to fit the larger 3/4 ton u-joints (the NP-205 T-case was from a 1/2 ton) and the rear driveshaft still worked fine,but I had to source a shorter front shaft,one 23" long vs about 28",I found that a 1969 K10 was the only year that used one that short and I lucked out and found a friend had that exact truck in rolling chassis form rusting in his woods!..

I did have to cut the floor hump,but that truck had a 2wd cab on it and I had to do some fabbing to make the 4x4 "hump" fit right,and the shifter on the NP-205 was mounted in a slightly different spot than the NP-203 was..I just used a BIG shifter boot and enlarged the existing cutout....the original crossmenber worked fine,no mods needed to bolt up the adapter from the NP-205..