1970 gmc jimmy dana 20/sm465

[Cadden]

I'm looking to put a dana 20 back in my jimmy. It came with a NP205 but it was always a tight fit as my jimmy originally had the dana 20 but the person I bought it from junked it before I bought the jimmy thinking it was a chain driven T-Case. I believe I would've needed the crossmembwr for the 205 to fit properly, but i somehow made it work. (Super tight fit against the body)

Long story short I can tell someone abused the snot out of this 205 and am having a few issues with it.

Anyways, since I don't really wheel this thing to crazily and never plan on going bigger than 35s, I want to put a dana 20 back in.

I've also always had issues with the shifter for the NP205 fitting thru the tunnel

My question is, is the adapter between the trans and transfer case the same for the 205 as it is the dana 20?

Come someone knowledgeable give me some insight?

 

[Hogback Fabrication]

Adapter is definitely not the same.

The adapter you're looking for is specific to that combo, and a rare one that was only an option for a couple years. Only available used (as 50+ year old used parts!).

Given the really small sales numbers for the first couple years of Blazer/Jimmy, and that Rockwell and New Process transfer cases both seem more common than the D20, I'd be surprised if 1000 of those were ever made.

The Dana 20 for your truck is pretty different from the Ford/International/etc. version too, pretty much the same in name only.

The NP205 you have is far more common and pretty easy to work with, parts are readily available. Other than the shifter in the floor, what problems are you having?

 

[Cadden]

Adapter is definitely not the same.

The adapter you're looking for is specific to that combo, and a rare one that was only an option for a couple years. Only available used (as 50+ year old used parts!).

Given the really small sales numbers for the first couple years of Blazer/Jimmy, and that Rockwell and New Process transfer cases both seem more common than the D20, I'd be surprised if 1000 of those were ever made.

The Dana 20 for your truck is pretty different from the Ford/International/etc. version too, pretty much the same in name only.

The NP205 you have is far more common and pretty easy to work with, parts are readily available. Other than the shifter in the floor, what problems are you having?

I need a new front output yoke on the case and it's 30 spline and obsolete, i havent been able to find one. One of the side tabs snapped off, the rear yoke was just as bad when I was putting it together (I hot the jimmy just a body on wheels and a truck load of parts basically) It also rubs on the body since I still have the crossmember from the dana 20. I had to lift the body up about an inch to get the transfer case to slide the rest of the way in.

I have access to a dana 20 but not the adapter, at least I don't think the adapter for the 3 speed trans is the same for the sm465

 

[Hogback Fabrication]

Unfortunately this is one of the rare instances where GM is difficult, pretty much every trans/t-case adapter is unique to the combo from the 60's through the 80's.

If the yoke in your picture is indeed 30 spline that would be a rare bird, one I've never seen on an NP205. They were on NP203's for a couple years in the mid 70's, that's the only place I've ever seen that one (and they're rare on 203's).

Wouldn't surprise me if the D20 crossmember was special, but fortunately the crossmembers from a 1/2 or 3/4 ton (including Blazers and Suburbans) would all work with your NP205 up to 1984. The right crossmember is probably a lot easier to find.

 

[Cadden]

At least I'm pretty sure i counted 30 here. It's definitely a 205 I've had it halfway apart looking for the source of the clanking sound after my sand dunes trip

 

[Hogback Fabrication]

GM NP205's had 10 spline front outputs up to '78 give or take. Then 30 spline for the rest of the run, but the 30 spline front outputs all used a flat/square flange.

GM NP203's generally followed that trend, but they didn't start until '73 and almost exclusively used the same 30 spline flat/square flange as the later NP205. GM also used a 1310 CV (early, basically first factory 4WD's in the 60's up to the late 70's) and a 3R CV late (say, late 70's and up for the square bodies).

I've seen a small handful of NP203's that had that yoke, they fit on an NP205.

I would definitely not say that it's impossible that an NP205 came with a 1310 CV yoke like that but I've dealt with hundreds of NP205's and never seen that. I'd bet someone swapped stuff around.

You might try ORD, they have a lot of that kind of stuff. If you can find a good yoke it would be a lot easier than swapping back to a Dana 20. Driveshafts and shifter would be specific to the D20 too.

 

[Cadden]

GM NP205's had 10 spline front outputs up to '78 give or take. Then 30 spline for the rest of the run, but the 30 spline front outputs all used a flat/square flange.

GM NP203's generally followed that trend, but they didn't start until '73 and almost exclusively used the same 30 spline flat/square flange as the later NP205. GM also used a 1310 CV (early, basically first factory 4WD's in the 60's up to the late 70's) and a 3R CV late (say, late 70's and up for the square bodies).

I've seen a small handful of NP203's that had that yoke, they fit on an NP205.

I would definitely not say that it's impossible that an NP205 came with a 1310 CV yoke like that but I've dealt with hundreds of NP205's and never seen that. I'd bet someone swapped stuff around.

You might try ORD, they have a lot of that kind of stuff. If you can find a good yoke it would be a lot easier than swapping back to a Dana 20. Driveshafts and shifter would be specific to the D20 too.

That's weird The drive shafts I used were from the dana 20 setup and everything seemed to bolt up the only thing not stock is the transfer case and adapter itself