75 K20 203 to 205 swap

[CarterDawson]

Hey guys, I used the search and read several threads that answered most of my questions. My truck is a 75 k20, 350/350/203. Looking to swap the 203 to a 205. I’m aware I will need different drive shafts. All that stuff is not a problem. I got connections and won’t have a problem getting the correct drive shafts. The 205 I have access to is out of a 1980 K20 with a 350/205. The trans/tcase are still paired. My question is, to my knowledge my 75 K20 should be 27 spline output, while a 80 k20 would’ve had a 32 spline? So how do I make that swap work. I don’t really want to swap transmissions as the one is my truck is super smooth. The one out of the 80 is in unknown condition. My other question is would the 80 have the slip in the transfer case, or is it in the drive shaft. I had a 80 suburban a while back with the 205. If I remember right the slip was in the transfer case. Is one better than the other?

I apologize if my terminology isn’t right. I’m trying to say everything correctly, but is kinda a lot to remember for a novice like myself. Thanks for your patience.

I apologize if I'm asking questions have been answered in previous threads. If so I would appreciate any links. And help or advice is greatly appreciated. Thanks

 

[SquareRoot]

Just swap the input shaft to the spline count that matches the trans. Slip in the shaft is always better. That means you have a fixed output on the trans. It's not required, depends on what you're trying to accomplish.

 

[75BEASTK20]

Hey guys, I used the search and read several threads that answered most of my questions. My truck is a 75 k20, 350/350/203. Looking to swap the 203 to a 205. I’m aware I will need different drive shafts. All that stuff is not a problem. I got connections and won’t have a problem getting the correct drive shafts. The 205 I have access to is out of a 1980 K20 with a 350/205. The trans/tcase are still paired. My question is, to my knowledge my 75 K20 should be 27 spline output, while a 80 k20 would’ve had a 32 spline? So how do I make that swap work. I don’t really want to swap transmissions as the one is my truck is super smooth. The one out of the 80 is in unknown condition. My other question is would the 80 have the slip in the transfer case, or is it in the drive shaft. I had a 80 suburban a while back with the 205. If I remember right the slip was in the transfer case. Is one better than the other?

I apologize if my terminology isn’t right. I’m trying to say everything correctly, but is kinda a lot to remember for a novice like myself. Thanks for your patience.

I apologize if I'm asking questions have been answered in previous threads. If so I would appreciate any links. And help or advice is greatly appreciated. Thanks

NP205 is bulletproof. Good stuff.

 

[bucket]

Hey guys, I used the search and read several threads that answered most of my questions. My truck is a 75 k20, 350/350/203. Looking to swap the 203 to a 205. I’m aware I will need different drive shafts. All that stuff is not a problem. I got connections and won’t have a problem getting the correct drive shafts. The 205 I have access to is out of a 1980 K20 with a 350/205. The trans/tcase are still paired. My question is, to my knowledge my 75 K20 should be 27 spline output, while a 80 k20 would’ve had a 32 spline? So how do I make that swap work. I don’t really want to swap transmissions as the one is my truck is super smooth. The one out of the 80 is in unknown condition. My other question is would the 80 have the slip in the transfer case, or is it in the drive shaft. I had a 80 suburban a while back with the 205. If I remember right the slip was in the transfer case. Is one better than the other?

I apologize if my terminology isn’t right. I’m trying to say everything correctly, but is kinda a lot to remember for a novice like myself. Thanks for your patience.

I apologize if I'm asking questions have been answered in previous threads. If so I would appreciate any links. And help or advice is greatly appreciated. Thanks

Sorry we seemed to have missed this question nearly a year ago.

But the important thing here is not the year. What's most important is the transmission. A th350 has a 27 spline output. A th400 has a 32 spline output. If the '80 K20 does in fact have a th350 (which it shouldn't, it should be a th400) then the np205 will bolt right in place of the np203.

 

[bucket]

Just swap the input shaft to the spline count that matches the trans. Slip in the shaft is always better. That means you have a fixed output on the trans. It's not required, depends on what you're trying to accomplish.

Swapping a 32 spline input into a 205 case that had a 10 or 27 spline input requires boring the case for a larger bearing. And it requires finding said input. A th350 to np205 adapter would also be needed, as the th400 to np205 adapter will not work.