View Full Version : turbo350 to turbo 400 tranny swap

john sheehn
08-11-2000, 10:41 PM
I've come across a turbo 400 tranny that was originally in a small bus. It was originally set up for an emergency brake at the tranny output. The output setup on this tranny looks identical to the output of my current 350. This tranny is in my 77 K20 pickup. My question is: will a turbo 400 swap out exactly with my 350? If not, what modifications will be necessary? Is the 400 any longer than the 350, necessitating changing mounts or driveshaft lengths? Since the turbo 400 I want to put in was set up for an emergency brake, is the output shaft the same as on a turbo 400 made to bolt to a NP203 transfer case?
It looks like it oughta work, but I'm just going from memory of the last time I had my tranny out. Any advice would be greatly appreciated. THANK YOU. John Sheehn :-)

09-09-2000, 12:21 AM
I was checking transmission prices today and happened to bring up the k20 350 to 400 tranny swap (I have a 1976). I didn't take notes (kicking myself now, because I'm considering the swap too) but the guy said is that the 400 is about 4 inches longer than the 350. Also, I believe he said that the output shaft is a different size, which means you need an aftermarket adapter of some sort to connect to the transfer case, not to mention changing the lengths on the driveshafts to both the front and rear axles. I got the information from a guy at a transmission rebuilding shop. If you have a similar shop (all they do is rebuild transmissions, all day, every day) in your town, give them a call. Those kinds of places usually have at least one guy that can give you the info you need.

Good Luck!!