ROUGH IDLE,CUTS OFF WHEN SHIFT TO REVERSE - 1995 Ford Econoline

under warranty
take it in for warranty service

You have a broken part inside the transmission, it will need to be torn down and inspected.

Would search first inlet air leak in between air box and engine - all hoses on, clamps tight no cracks
then disconnect idler control - about where the engine accelerate cable comes in / most probably opposite. Problem still there?
look for ignition - plugs, check leads with multimeter, connections

Sounds like it may be a faulty TCC clutch solenoid. Torque Converter Clutch. The TCC solenoid is located in the transmission valve body located directly under the transmission oil pan.

check for vacuum leaks,the throttle position sensor and the map sensor to see if they are working correctly.

I'm sure your check engine light is on try....
https://www.autozone.com/landing/page.jsp?name=top-five-reasons-check-engine-light

For this types of problem,there are few help inks to troubleshoot the problem.Click the link below to go through the troubleshooting procedure to resolve the issues :----Idles rough and quits when gas pedal is pressed less? http://technoanswers.blogspot.in/2012/01/1999-ford-f-150-idles-rough-and-quits.html-----------van idles rough? http://howtobyme.blogspot.in/2012/01/2004-ford-freestar-van-idles-rough.html
--------------runs lean and idles rough? http://technoanswers.blogspot.in/2012/02/ford-runs-lean-and-idles-rough.html
-----------Car still runs Rough after tune up? http://howtobyme.blogspot.com/2011/12/car-still-runs-rough-after-tune-up.html
------------Idle flair is noticed on car? Rough idle? car will not idle? Erratic idle speed? http://technoanswers.blogspot.in/2012/02/idle-flair-is-noticed-on-car-rough-idle.html
----------High rpm in neutral? Inconsistant high RPM in neutral? http://technoanswers.blogspot.in/2012/02/high-rpm-in-neutral-inconsistant-high.html
------------Engine Backfires? http://technoanswers.blogspot.in/2012/02/jeep-backfires.html----------- Nissan stalls and bucks on Acceleration?

http://technoanswers.blogspot.in/2012/02/nissan-pathfinder-stalls-and-bucks-on.html

-----------
Nissan Pathfinder Backfires? http://technoanswers.blogspot.in/2012/02/nissan-pathfinder-backfires.html
---------How to adjust rpm? http://schematicsdiagram.blogspot.com/2011/12/how-to-adjust-rpm-on-2009-dodge-charger.html
------------Engine cuts out at 3000 RPM? http://schematicsdiagram.blogspot.com/2011/12/engine-cuts-out-at-3000-rpm.html
----------This will help.Thanks.

o-2 sensor

As far as the transmission issue is concerned, it sounds like you may have a clogged filter, and are in need of a fluid, and filter change, but that is best case scenario, worst case is you need some serious transmission work performed. The rough idle, could be due to bad plugs, a faulty MAF-mass air flow-sensor, or TPS-throttle position sensor. I would have a diagnostic ran on the van and see what codes come up.

check idle how many rpm is it running