Is there a difference between any of the N/A transmissions? Or are they all the same? Would I be able to take one from a 91 and put it on an 87, etc?

 

they are interchangeable im pretty sure, of course the auto is different

 

Vert ones are the only ones really different for non turbo trannies (other than minor gear and syncro differences).

 

You'll need to use the crossmember from the transmission. It'll bolt to the car the same, but the way it bolts to the transmission is different between the S4 and S5.

 

How so? I put a S5 from a coup into my Vert and bolted right in (caveat with my comments below). I know the speedo gear on a S4 vert is different, but same on S5 verts.

Are the internals somehow different (ie beefier due to the extra weight)??

One thing not said yet is the S5's and S5 tranny's, na or Turbo, have different tranny mounts. So, if want to put a S5 in a S4, you need a S5 tranny mount and the bracket the mount bolts onto. You should also replace the two little square rubber mounts with new, otherwise you setting yourself up for premature tranny mount failure.