I drove about 5-6 miles after replacing old tranny with new(to this car) It shifted properly and all seemed fine. As I pull into the drive I lost drive motion. I jacked it up and checked to see; TC working, Rear end working, linkage operating smoothly, driveshaft turning when rotating rear tires manually. The first thing I thought to check was the vacuum to the modulator and it had split so I replace the hose and it didn't help. Any ideas on where to start looking for possible failure? I have heard the term "burned up the tranny" but there was no slipping or noise or anything....it just stopped working.Thanks

 

Check governor gear to see if it is stripped (apple core).

 

Not sure where or what that is. Another question is, does it matter which line goes to the bottom or top on trans cooler?

 

It doesn't, but I usually like to run the trans out to the bottom of the cooler and trans in to the top. This is how OEM does it. If the fittings are parallel to the road, I would just plumb it whatever looks the cleanest.

The governor is the round cover near the tail shaft housing on the drivers side. There is most likely a heavy spring clip that goes over the cover, you will need to carefully use a chisel to remove the cover.

 

How careful were you in seating the convertor properly?
The pump gears at front of trans driven by the convertor supply the fluid pressure that makes everything work ;
if they aren't being driven then you have no motion

The stock TH350 pump gears are only powered metal .I took out 3 sets under similar light driving circumstances to you
I was young and didn't know any better , the dodgy trans builder kept blaming me for not installing the convertor right and continued to fit factory gears.
Finally went to another guy and 1st thing he said was TH350 have weak pump gears and fitted steel ones.
Four years of drag racing on that trans and never blew them again

FWIW
Neither the governor or the modulator will make it totally lose motion, they only affect the shifts ( or not)
Car would still have reverse

 

What other said above. Plus thought I would mention do you have enough trans fluid in it? It's free and worth checking again. Crank the car, cylethrough each gear, put it back in park, check while running. Also smell the fluid and see if it smells like burnt electronics/plastic.