NP205 swap.

[JAKES 68GMC]

What is involved in swapping out a Rockwell 221 t-case for a NP205? What parts do I need to do it? What will I need to modify??

If you have swapped out your Rockwell for a NP205, please post everything you did in the swap.

[shelby987]

I am looking at swaping a dana 20 for an NP205....I was told that it sat 1" lower........there is a jeep site that brakes down all the transfer cases.....someone posted the link in a post that I had.......I believe it had all the dimensions of the transfer-cases.....that will tell you if you need new driveshafts.....you might need new yokes, not sure what the spline counts are on the rockwells.....ttt for you!

[JAKES 68GMC]

ttt.......

[1969 GMC]

I made a thread about this a while back. IIRC, the x-member needs to be moved 1.5" back. The bracket from the transfer to the frame worked on the 205. Also, driveshafts need to be lengthened/shortened accordingly. You'll also need to cut a new hole in your hump for the shifter, or get a hump out of a 205 original truck.

EDIT: when you get your 205, make sure to get the adapter, the adapter sleeve (both different than the 221's), the shifter and linkage piece. It's best to find a donor vehicle.

[JAKES 68GMC]

Will the splines be the same for Rockwell and NP?? Can I use the driveshafts out of a 67-72 parts truck with a np205?

[1969 GMC]

Originally Posted by JAKES 68GMC

Will the splines be the same for Rockwell and NP?? Can I use the driveshafts out of a 67-72 parts truck with a np205?

The splines are the same, 10. I would guess that the driveshafts out of a 205 donor would work, but I never got that far (found a bunch of problems with my truck so it has sat).

[JAKES 68GMC]

Ok, so if I get an NP205 parts truck, I will have to have:

transfer case (duhhhh)
adapter
sleeve for tranny to t-case
move the t-case crossmember back 1.5 inches(maybe)
Lengthen or put differnt driveshafts in.

After that, its pretty much straight-forward?

[1969 GMC]

Like I said, mine didnt go on the road after I finished it, so I can't prove that it worked out great. But everything went together good and it should be fine if it did drive (this is the fine print, LOL)

you don't HAVE to move the x-member back...if you dont want the t-case adapter supported. The 465/205 adapter is longer than the 465/221 adapter.

[JAKES 68GMC]

You've got me lost with the crossmember. Wouldn't you HAVE to move it back so the t-case adapter WOULD be supported??? The adapter is what mounts the t-case on my truck, it bolts up through the crossmember in to the threads in the adapter.
Just trying to bet the info straight so I can get this swap done right. Thanks for your help.

BTW, whats wrong with your truck????

[1969 GMC]

ohh, i read your post wrong when you said move the crossmember back (maybe). I'm pretty sure its 1.5 inches. yeah, the adapter feet bolt to the crossmember.

there is a lot wrong with my truck, lol...it's been parked for a while.

[JAKES 68GMC]

Thats what I thought. I couldn't quite figure out how the t-case would stay mounted without the x-member. Thanks for your help.

[68-BEAST]

I have a 68 GMC Suburban, 4x4, 3/4 ton, SM465 4 speed and it originally had the Rockwell Transfer Case in it. I have done the swap to an NP205 and have road tested it with no problems. You are on the right track with all of the posts here. You will need:

NP205 txfer case. (obviously)
Adapter
Sleeve from tranny to transfer case (make sure it is not worn too bad)
Gasket between SM465 and adapter (local Chevy dealer got it in 1 day / $3)

You will need to move the crossmember, 1.5 " sounds about right but I didn't measure it.

You will need to lengthen the front drive shaft (barely) and shorten the rear drive shaft. A local guy made me a new rear driveshaft with a full rubber boot and installed it for $100.

My NP205 came already attached to the adapter so it made things a little easier. You will also need to cut a larger hole in the tranny hump, the shift pattern on the NP205 is different than the Rockwell and it seems to need alot more room to shift.

Email me with any questions, I would be happy to answer them
collins512@peoplepc.com

68 BEAST

[Yukon Jack]

Welcome to the board 68-Beast, that is great info you posted.

[JAKES 68GMC]

Yup, the 205 is in and all bolted. All I need is a 3/4 ton 205 yoke for the rear output, and reworked driveshafts. I didn't measure the length for how far back the t-case had to go, either. We just bolted the 205 up the the tranny, bolted the crossmember to the t-case, and jacked it up so the x-member was level with the (no gap between member and frame), and then drilled.
I've got 3 questions for you, 68 Beast
1. Did you use the Rockwell crossmember?
2. Does the 205 rub against your floorpan??
3. How did you drill you top holes for the x-member??? (we used a foot-long 3/8 drill)

[CUSTOM/10]

Jake

I believe that there's about a 1" difference in the height of the 221 & NP205 cross members. The 205 being the taller of the two. If you use the 221 cross member that's why the 205 t/c rubs the floor.

Gary

[68-BEAST]

Great to hear that you got it bolted in!!

I did use the Rockwell crossmember and it doesn't rub against the floorpan. I'm not sure what you mean by "top holes for the x-member." My swap was done on a 68 Suburban and the cross members I have bolt to the bottom of the frame, so it was easy to just jack it up and drill the new holes in the frame from the bottom.

Do you mean the two holes in the middle of the crossmember that hold the t-case?? I did this 5 years ago but I think the holes matched up with the NP205 and I didn't have to drill new ones.

68-Beast

[JAKES 68GMC]

Nope, the X-member I have is 3 pieces. It has two pieces that are riveted to the crossmember itself. The riveted pieces bolt to the upper lip of the truck frame on each side, therefore the t-case is bolted in both the top and bottom lip of the frame. 4 bolted spots instead of 2. ( Maybe the X-members are different for 'burbs than for pick-ups.

My 205 just rubs a little bit on the floors. Put in some cab mounts and there'd be no issues with rubbing. It's nothing serious, I'm just curious.

[68-BEAST]

The crossmembers must be different, my suburban x-member is 1 piece and bolts to the xfer case with only two bolts. When I did this switch I replaced all the old bolts with new shiny ones. . . with the same strength ratings.

68-BEAST

[JAKES 68GMC]

the X-member in mine looks sorta like this:
_ _
_\_____________/_

The top pieces are one piece, and they are rivited to the main x-member(long bottom line) to brace it. Thus, when the rivets are cut, it's 3 pieces. The two rivited pieces bolt on the upper frame lip, while the main x-member bolts to the bottom. Kind confusing without pics, but oh well.

BTW the 205 in my truck works fine so far. I haven't driven it all the much, just a few trips around the camproad. The engine needs to be tuned to run good with the Holley. Timing and carb adjustments mostly.

[68-BEAST]

That is a great picture Jake. I understand what you are talking about and how it looks. Mine is different, just one piece and it only bolts to the bottom rail, two bolts per side. I guess that made my swap a little easier.

68-BEAST

[1969 GMC]

Originally Posted by 68-BEAST

That is a great picture Jake. I understand what you are talking about and how it looks. Mine is different, just one piece and it only bolts to the bottom rail, two bolts per side. I guess that made my swap a little easier.

68-BEAST

Wow, that would have been nice. Drilling the new holes in the upper part of the framerail, while laying on my back in the gravel drive, with all the rust flakes and hot metal shavings landing in my eyes, all while trying to NOT drill holes in the cab floor, definitely brought the suck. My x-member looked like Jake's.

[JAKES 68GMC]

It was actually pretty easy. We had a foot-long 3/8 drill (what are the odds?) kicking around the shop, and we drilled right through the bottom lip, and up in to the top lip through the same hole. The bit was quite dull, but it worked.

I take a good deal of pride in my artistic pic shown above.

[68K20 x Drill]

I used a squarebody crossmember, remember drilling some holes, and nothing rubs.

[mudmizer]

I made the swap in my 68 and it sounds as if it all went just as yours did. Really fairly simple. I also used the long bit, tough looking job made easy by the bit. I have a 2" body lift so there was not a concern about rubbin the cab. After makin the new hole on the right side of the floor cover and welding up thr old hole, I cut a small piece of carpet frum under the seat and hot glued it over the new patch plate. Can't really see the old shift hole at all.