SM456 to Automatic

[wedgemon]

I'm considering a swap from my SM456 to a TH400 or 700R4. This would be on my 1980 K10 4x4. So, the NP205 would stay - I think.

I did a Google search and a site search and found little to nothing.

Any ideas or write upd you could link me to would be greatly appreciated.

Thanks!

- Dave

[Russell]

The 700r4 / NP205 combo would require an aftermarket adapter, and the TH400 / NP205 combo is a highly sought after and therefor expensive setup.

Is there a certain reason why you want to keep the NP205? An NP208 or NP241 can be bolted in without too much difficulty, is lighter, has a better low range and opens a lot more options for transmissions.

[DirtyLarry]

I did just the opposite about 10 years ago to my 1978 K10. I ditched a TH350/NP205 for a SM465/NP205…..now I wish I had a NV4500 with overdrive instead. When I got the truck in 1996 it actually had a NP203 transfercase but I swapped that out for a NP205 very shortly after I got it.

Fast forward a few years to 1998 and a buddy and I scored a nice 1976 K10 swb with a 465/205 back home in CO. We bought it and hauled it to Detroit where I lived at the time and swapped piece for piece to each truck. Then we sold the donor for a pretty decent profit after the auto swap as it was a rust free CO truck sold in MI. Actually some dude from OH drive up to Detroit and bought it. It was a POS ranch truck by CO standards but this guy was drooling over it.

Anyway, it was actually a very easy swap if you have a complete donor truck at your disposal to pirate parts from. Converting the donor to an automatic was a hell of a lot easier than converting mine into a stick as drilling cross-member holes in the frame was a cold PITA under a car port in Detroit in January! At the end of the project we actually made money by selling the rust free donor truck in the Midwest even considering the fuel to trailer it out from CO and the 465 conversion into my truck cost me zero....even paid for my Centerforce clutch. Midwesterners seem to favor automatic transmissions over manuals anyway and rust free sheetmetal is a rarity for them. Good for them…but my style of off-roading is all mountains (now that I live back in CO) where a manual is the tool to have.

Long story short…..if you have a complete donor truck everything goes much smoother but you would be wise to go swap in an OD trans if you are going to swap in something but then you will need an adaptor to mate your NP205 to a 700R4. If you are not seriously into off-roading don’t get hung up on the NP205 thing….settle for a NP208, NP241, etc that would be in the donor truck. Don’t forget to grab the drive shafts too…