What do I have to change in order to swap a 700R4 to a 400??

 

you will most likely need a new drive shaft depending on weither or not you have a short or long tail, you will need an adapter plate so you can mount the th400. speedway magazine sells the plate for about $50

going to need a custom tranny mount, and a custom traction bar mount, as well as a new shifter (b&m megashifter works well)

it may be slightly different for you, as i did my swap in an '88 trans am gta w/ 350tpi l98 w/ a '74 TH-400

 

adapter plate for what? They make chevy th400

 

Here's what I did, and no need for an adapter plate, it bolts right up to the engine. Bought a Spohn crossmember and torque arm for the TH400 swap. Used the stock driveshaft since it was the right length and swapped on a TH400 slip yoke. Since my car was a 3 speed auto already (TH200c), there wasn't any need to change the shifter. The speedo cable threaded right in and the cooler lines did the same. You could also get a custom crossmember made and pick up a bracket kit for the stock torque arm to mount onto also but personaly, I like having the torque arm mounted to the crossmember. Less stress on the tail of the transmission and less chance of busting a transmount. Here's a couple of pics of my setup.

 

OOOOOOHHHHHH, thank you very, very much!!!!!
I at least have the B&M megashifter and it seems the rest is pretty straight forward.

 

To dont need the Megashifter either, if you didnt want to spend the $$$. You can use the stock one, it works fine.

 

Just thought of another thing I had to do. You need manifold vacuum to the vacuum modulator on the trans. Use some metal tubing for the majority of it and rubber line for the ends. Also, if you want to hook up the electric kickdown, there's a kit you can get from Summit Racing. I haven't done that, because I usually just kick it down myself.