Np203 to np208?

[Magic1]

Got an 82 Sierra with a 350 tranny and 203 case. I've found a guy parting out an 86 model with a good 208 that he said he'd take 100$ for. My case needs work or replacing so I'm wondering what it would take to make the swap. He's keeping his tranny or I'd just buy it all and swap everything. I know the 208 probably isn't near as stout as a 205 but hey, 100$!

[Captkaos]

I think they will swap, but don't rightly remember...

[Jason S]

The transmission output shaft will need to match the NP208 input and have the correct T-Case to Transmission adapter.

The Chevy NP208 is slip yoke output on the rear, while the NP203 is a fixed yoke output, plus other minor details. $100 is probably a good price, but there are the little details that can get expensive...

[roboticjunky]

As long as the NP208 came off of a 350 Turbo or 700R4, it will have 27 splines on the input gear. It would work on your truck since it has a 350 Turbo.

If it came off a later style SM465, any other newer style stick, or 400 Turbo, then it would be 32 splines and wouldn't work.

Earlier SM465 has, I think, 10 splines for the input gear.

You're need an adapter for the 350 Turbo to NP208, which "might" be the same as the 700R4.

[Magic1]

Are you sure about that? Cause if it will work with just swapping out the adapter ill give him 100$ in a heartbeat!  Would the original driveshafts work or would they need to be replaced as well?

[roboticjunky]

After some research, 350 turbo (with a np203) has a shorter output shaft. 350 turbo with a np208 (which was 81 and 82) had a longer output shaft.

This adapter kit from Advance Adapters will make it work.
http://www.advanceadapters.com/products/pn-50-7100/

You're also need the shifter for the transfer case, the torque rod (rod that goes from the side of the transfer case to transmission bell housing), driveshaft with a slip yoke, and probably the cross member.

[Magic1]

Yeah I'd already looked that adapter up but it says no driveline mods needed in a side note on that page. Guess ill have to call em and see if my shaft will work?

[Jason S]

Before you drop $100, I would recommend a little more research... 

Like I said above, $100 for the T-case sounds good. 

However, if you have to spend $100 for the T-case, $100 or more for a T-case to transmission adapter, a $100 for an output shaft (plus other extras, like shifters, driveshaft shorten/lengthen) you might come out ahead by just buying the transmission & t-case and drivelines (with adapters and all) from a salvage yard. As an example, I recently acquired a 700R4 mated to a NP208 and all the extra parts (strut rod, crossmember, front driveshaft, t-case shifter, wiring, shifter boot, etc.) from a small town salvage yard for $300 (pulled out and loaded). 

Here are a few additional things you might consider:  What is it going to cost to swap in the NP208 (considering adapters, driveshaft mods, etc.) versus repairing or simply replacing the NP203? For the long run, are you going to stay with the TH-350 or are you planning a swap to a manual or an overdrive auto transmission?

[Magic1]

That is a good point. I'd love to swap over to a manual tranny but I just had the transmission rebuilt so it would be silly to go that route now. I checked into rebuilding my tcase and its gonna run around 500$ or about 750$ if mine can't be rebuilt and have to get a remanufactured one. I was just thinking that if I were gonna have to shell out tha kind of money I may as well swap to something else. The easiest fix would be to just repair/replace what I've got but figured I'd get ideas on what the best route would be to go. The tcase is gonna be the last thing I'm gonna do after I finish the body and replace the motor so I've got a while.

[Irish_Alley]

like jason said you prob looking at just a couple hundred in drive shaves plus the adaptor so you be spending close to 500 for a np208 when you can just go buy a used 203 for 200 depends on where you live but you can get one, for a couple 100 cheaper. go to a junk yard if you need or search online.