Need quick answer: 4x4 tranny swap

[orangeuavol]

I need to know if there are any differences between a factory 3-speed in a '72 4x4 and an automatic (turbo 350 or 400). The transfer case is the variable that I don't know about. Are the mating problems?

[FRENCHBLUE72]

If you swap in a th350 or 400 you are gonna need the adapter for the t-case to tranny..

[orangeuavol]

I'm looking to buy a blazer that has a three speed, but my wife can not drive a standard (tried teaching her but don't have the patience).

[orangeuavol]

Thanks frenchblue72! Is the adapter just a shortened yoke?

[orangeuavol]

is the auto shorter or longer than the tranny?

[JimKshortstep4x4]

The TH-350/NP205 is a direct swap in for the 3 speed setup. You can use your existing driveshafts and crossmember. I would suggest buying the TH-350/NP205 setup from someone on the board. The adapters are available but can be pricey. The adapter is the part between the transmission and the transfer case and it has the mount cast into it.

Jim

[orangeuavol]

Thanks for the info guys.

[Vince M]

A new T-case adapter for the TH350 to NP205 runs about $250+ from GM. Be very careful buying a used one. They have a tendancy to crack and it's not always easy to see where. Good used ones are hard to find.

[jhow66]

Anyone know who this ORANGEUAVOL guy is? (ssshhh I am his dad) He ask me -I said ask you guys. Thanks for the quick replies.

[mrein3]

If you're going to change to an auto you need both the transmission and the transfer case.

The input shaft to the transfer in your manual has 10 splines. The input shaft on the auto tranny transfer case has 28 splines.

The "adapter" is the piece that goes between them. It isn't an adapter in the sense that you can bolt this piece to this piece with this adapter. They all came from the factory with an adapter. The 3-speed to NP205 is different from the 4-speed to NP205 is different from the th350 to NP205. And as Vince pointed out, they do crack. In fact I've never seen a used one that wasn't cracked.

Buy a th350, adapter, and transfer case ahead of time. Split them and check for cracks in the adapter. Check for wear in the drive sleeve that rides in the adapter. The drive sleeve rides around on the oil seals on each end of the adapter. These seals are what keep the tranny fluid in the tranny and the gear lube in the NP205.

As others have pointed out - once you have yourself a complete tranny/adapter/transfer (th350/adapter/NP205) it is a direct replacement for your manual/adapter/NP205.

[orangeuavol]

Thanks MREIN3

[Blazer1970]

If you are buying a '69 - '72 Blazer with a 3 speed, it will have a Dana 20 transfer case. There is no way to use this t-case with any automatic tranny. You need to find a complete TH350/NP205 with the adapter. You will also need the crossmember under the adapter, or you will have to figure out a way to space yours down about an inch or so or the 205 will hit the floor pan. The 205 shifter also comes up in a different place than the Dana 20, so you should get the hump from the donor truck if you can, or you will have to cut a new hole and plug the old one in yours.

[mrein3]

Originally posted by Blazer1970
If you are buying a '69 - '72 Blazer with a 3 speed, it will have a Dana 20 transfer case. There is no way to use this t-case with any automatic tranny. You need to find a complete TH350/NP205 with the adapter. You will also need the crossmember under the adapter, or you will have to figure out a way to space yours down about an inch or so or the 205 will hit the floor pan. The 205 shifter also comes up in a different place than the Dana 20, so you should get the hump from the donor truck if you can, or you will have to cut a new hole and plug the old one in yours.

Are all Blazers with a 3-speed factory equiped with a Dana 20?
I swapped out a 3-speed/NP205 from my truck that was originally a 1971.

I can't believe GM would keep putting 3-speed/dana 20s in Blazers on the same line that was putting 3-speed/NP205s in trucks.

Sounds like orangeuavol needs to figure out what transfer case is in that Blazer.

[jhow66]

We are going to look at it tomorrow and he "hopes" to buy it. will let you know the details.

[orangeuavol]

Wish us luck!

[Blazer1970]

Are all Blazers with a 3-speed factory equiped with a Dana 20?

I have never seen or heard of a Blazer from this era with a column shift 3 speed and a 205. In fact, they continued to use the Saginaw 3 speed/Dana 20 combo through at least the '74 model year in some Blazers/Jimmys. Are you talking about a column shift 3 speed, or an SM465 granny low 4 speed? SM 465s definitely came with Dana 20s in some Blazers, and 205s in others ('71 and '72).

[mrein3]

Originally posted by Blazer1970


I have never seen or heard of a Blazer from this era with a column shift 3 speed and a 205. In fact, they continued to use the Saginaw 3 speed/Dana 20 combo through at least the '74 model year in some Blazers/Jimmys. Are you talking about a column shift 3 speed, or an SM465 granny low 4 speed? SM 465s definitely came with Dana 20s in some Blazers, and 205s in others ('71 and '72).

I removed a perfectly good and servicable 3-speed column shift manual with a NP205 attached and replaced it with a rebuilt th350 with a NP205 attached to it. I sold the 3-speed to another board member from Iowa who had one that was wearing out and gave the 205 to the guy that helped me do the swap.

Now that I think about it I got the th350/NP205 out of a 1972 Blazer after da-burb tipped me off to a guy parting it out. I unbolted the thing myself as the guy had the tub and front clip already removed.

Since that Blazer had the 205 why would GM bother with the other transfer case? Unless two different plants had two different supply lines which is entirely possible.

Another possibility is the 3-speed/dana 20 uses same crossmember as 3-speed/205. And I know the 3-speed/205 crossmember is the same as the th350/205 crossmember. GM made them all (205s anyways) fit the same crossmember by having them bolt on with the adapter between the two pieces.

[Blazer1970]

I would bet that the 3 speed/205 was swapped from a truck into that Blazer, but anything is possible.

[jhow66]

Hey guys we bought the Blazer-it is a Dana 20.

[bouncytruck]

If you bought the rig, you have an obligation to post some pictures!

[jhow66]

Will do. Got to get battery for dig. camera. It is a real straight truck- of course it has the usual rust for these trucks -all have been fixed-purrs like new kitty-tracks straight as a arrow-sits square-body lines good-doors shut good -rear hatch has usual broken latch. He is real happy with it. Pictures later.

[Davy]

yep, we gotta have pics.