Shopping around for TH350/TH400 and came across the BOP TH400 offered on Jegs for $1200. It says it has a 4" short tailshaft. Does this mean this would be a direct swap like the TH350 without needed to make any of the modifications?

TH350 Overall length 27 5/8 in.
TH400 w/ 4" tailshaft Overall length 29"

https://www.jegs.com/i/JEGS/555/60315/10002/-1

 

Short answer: No.

Longer answer, also no.

 

No, it is not a direct swap and will require a driveshaft change or mod.

 

Specifically:

Shorter driveshaft
Different front yoke
Relocated trans crossmember
Different front and intermediate e-brake cables (due to the relocated crossmember)

 

And a kick down switch.

 

Got it. I always thought the long tailshaft was 6" instead of 4". Th350 is going to be the quickest and cheapest swap I think.

 

DOH! I should have caught that. Of course, that also means that you either need to change the accelerator pedal or cut off the tab on the pedal that the TH350 kickdown cable attaches to. This tab gets in the way of the TH400 switch.