(4x4) 4 speed swap to overdrive automatic?

[Kings71]

I recently purchased a great little 71 Chevy SWB 4x4 and want to make it my daily driver. I want to swap out the 4 speed with the NP205 transfer-case to a over drive transmission all while trying to keep the NP205 .. any ideas on the best way to go? thanks Steve

[87Skier]

It really depends on how far in you want to get. The NP205 that came behind the SM465 (Guessing you have the stock transmission) used a 10 spline input shaft that had a coupler that went between the transmission and transfer case.

The turbo350/np205 setup used a 27 spline male to male with a coupler and the the turbo400 version of the NP205 used a 32 spline FEMALE input. The transfer case is also slightly different between the th350 and th400 since the 400 used a larger input bearing but you can take apart the transfer case, have it machined to fit the larger bearing and run whatever you need.

You could go with a 700R4 which would have a 27 spline output shaft, but you have to change out the shaft to use a stock setup. This is the shaft you would need: Advance adapters

Then you need the stock parts.
Here is the what the adapter looks like: NW Fab
And the required input shaft: eBay
Coupler: eBay

Then you need the bearings and internal seals for the adapter. Plus you need to set up the transmission.

You could also go with a newer electronic transmission like a 4L60E which would be a lot easier to tune. The early (up to 97ish and back) 4L60E uses the same output bolt pattern and spline as the 700R4, which means you would need the same parts as above as well as a transmission controller, like this one: SummitRacing

You could go with a 4L80E which would require the same controller, but would require a 32 spline female input shaft (which you could swap your NP205 over to) as well as an adapter. This is the kit for that: Advance adapters

There are other ways of doing the swaps, like getting new cross members and using later style transfer cases. You could just get a working 700R4 and transfer case from a donor vehicle (junkyard, craigslist...) with the cross member and throw that in.

[Bigdav160]

I think the OP might be thinking of manual trans. The options are limited as OD manuals are getting harder to find and more costly

[Kings71]

Originally Posted by 87Skier

It really depends on how far in you want to get. The NP205 that came behind the SM465 (Guessing you have the stock transmission) used a 10 spline input shaft that had a coupler that went between the transmission and transfer case.

The turbo350/np205 setup used a 27 spline male to male with a coupler and the the turbo400 version of the NP205 used a 32 spline FEMALE input. The transfer case is also slightly different between the th350 and th400 since the 400 used a larger input bearing but you can take apart the transfer case, have it machined to fit the larger bearing and run whatever you need.

You could go with a 700R4 which would have a 27 spline output shaft, but you have to change out the shaft to use a stock setup. This is the shaft you would need: Advance adapters

Then you need the stock parts.
Here is the what the adapter looks like: NW Fab
And the required input shaft: eBay
Coupler: eBay

Then you need the bearings and internal seals for the adapter. Plus you need to set up the transmission.

You could also go with a newer electronic transmission like a 4L60E which would be a lot easier to tune. The early (up to 97ish and back) 4L60E uses the same output bolt pattern and spline as the 700R4, which means you would need the same parts as above as well as a transmission controller, like this one: SummitRacing

You could go with a 4L80E which would require the same controller, but would require a 32 spline female input shaft (which you could swap your NP205 over to) as well as an adapter. This is the kit for that: Advance adapters

There are other ways of doing the swaps, like getting new cross members and using later style transfer cases. You could just get a working 700R4 and transfer case from a donor vehicle (junkyard, craigslist...) with the cross member and throw that in.

Thanks for all the great information and links, I will be checking them out after work today. I have been thinking about a donor but am not sure which years would be the best to hunt down?

[1969C10t]

Check into a divorce mounted 205. I shade tree converted mine off a sm465 to a divorced case. Then the transmission swaps are as easy as a 2wd. If planned out good on a long bed the drive shafts can be the same length. I didn't expect mine to hold up very well but it has been a backup daily driver for 8 years now. Works good but the t-case shift linkage is a little spongy. Don't forget about the passenger side front diff offset.

[57taskforce]

There's also a spacer you can use to bolt between the trans and np205 that will allow you to keep the original output shaft in the 700r/ 4l60e. It will move the transfer case back a little but it is an option if you don't want to have a trans shop year down your transmission.

[msgross]

and then don't forget about your driveshafts since they probably won't be the right length once you're done.

Some of the 4x4 build threads in the 4x4 section have made swaps http://67-72chevytrucks.com/vboard/f...splay.php?f=30