NP435 2wd-4wd swap

[fireguywtc]

I don't know if this has been posted already, but I couldn't find anything similar so I decided to do this writeup. I recently decided to swap out the NP435 that came from the ol' 67 since it worked fine and the one in my 70 4x4 had some issues and noises. The swap was all together pretty easy but I ran into a couple of issues that I would like to share with all of you if anyone else is considering doing the same thing in the future. As I understand it this is a pretty common swap since there are more 2wd transmissions then 4wd. Keep in mind this swap was into a 4wd F250 with the divorced transfercase which shares more common parts then the F100's with the married tranfercase.

One of the most common known facts is that the output shaft and case is identical. I took a couple of pics to show the similarities and differences. The 4wd output shaft case is the same dimensions but has bolts to mount the transfer case shifting linkage and does not have a provision for the speedometer cable. The 4wd trucks have the speedometer cable located in the transfer case. Also the output shafts themselves are identical but the 2wd shaft had the plastic speedometer gear. I forgot to take a pic, but I left the gear on it since it will not hurt anything, but I did take a pic of my 4wd output shaft that is without the gear.





Also since I was doing this swap low budget, I made my own gaskets. For the output shaft gasket I wanted to point out the there is a cutout in the lower left part that lines up with a hole in the trans case itself. This is to allow gear oil to drain back into the trans and if you make yourown gasket make sure you trim out that area to allow for proper drainage. It was easy enough, once I cut out the basic shape for the gasket I put it onto the case and cut out the drain part with a razor blade.




Another difference is simple enough to swap out but I just wanted to show you to see the difference. The reverse light sensors are mostly identical but seem to have a different electrical connection in later years. The red one (70 model) has a more protective fastner to keep the contacts clean and dry better. The nut size (3/4) is the same as are the thread size and depth, so it is a direct swap.



Another issue that I was not aware of before the swap is the different size in the shifters themselves and the shift towers on top of the transmission. I knew the 4wd shifter was a different shape to accommodate the transfercase shifter, but it also has a shorter shaft portion from the pivot point that goes into the transmission. This means the tower on the top part of the case is also taller. (Forgive me since I don't know all the proper terms.) This is a simple remedy though as you transfer over the tranmission tops with the shifters as they have the same bolt pattern and internal linkages.




The only part of the swap that was completely identical was the output yolk.



Again overall the swap was realtively easy, but I though I would share my experiences to help others shoud they want to try this swap.

[mlheppl]

Excellent info Bill. I was unaware of the differences between the 2wd NP435 and F250 4X4 NP 435. I thought that they were the same transmissions. I'm getting ready to put a 78 NP 435 w/ a married 205 transfer case into my 71 4X4. I may have to make a similar thread. Good job.
Mike

[71highboy]

thanks for the info