How difficult is it to swap a TH350 for a TH400?

[Cali4nia Monte]

Just curious how hard it would be to replace my current TH350 with a TH400. What if any modifications would be necessary?

 

Thanks,

Mike

[Mike Brichta]

Hi Mike,

 

I did this a few years back and I will try to list all of the things that I needed to switch/purchase:

 

1) TH400 trans will bolt up to engine without any problems assuming it is a TH400 with a chevy housing.

2) I needed to purchase a TH400 yolk for the driveshaft. TH350 is different.

3) I needed to shorten the driveshaft about a inch or two.

4) I needed to purchase a "kickdown" setup since the TH400 downshifts using a switch instead of a detent cable. The setup has a lever part and an electronic switch for downshifting. You can simple remove the detent cable from the engine compartment.

5) I needed to make two wires for the downshift switch. One goes from the downshift switch by the gas pedal to the "IGN" post on the fuse block (to supple current to the switch) and the other goes from the switch to the transmission downshift switch on the transmission.

6) I had to move the trans crossmember back to the next set of holes on the frame since it needs to bolt back further than the TH350.

 

There may be some other minor things to deal with but that's pretty much it.

Mike