Land Rover Repair: New VSS didnt work- Try new TPS now?, speed signal, vss

Question
Hello- we had our transfer case replaced 5 months ago and 4 days after we got it back out of the shop the speedometer stopped working. It would actually work here and there for about the first month after it started to die, at least until we turned the engine off. Also, when we come off the freeway or take a turn slowly the RPMs go way down and the engine just shuts off- not stall and rattle, just shuts off completely! We replaced the VSS a few weeks ago and it didn't make the speedometer work until 2 wks later it actually came on a few times for a few seconds here and there but it wasn't smooth, the needle jumped around quite a bit and it never worked again since. The check engine light is still on and the idle is still low and the needle won't move and the odometer won't budge as well! We unhooked the battery and the engine light came off until we went on the freeway and went fast-then it came right back on.  Do you think the TPS is what we should replace next? We assumed it was the VSS that went bad because of the transfer case being replaced just a few days before the symptoms started.  Please give any advice or insight that you can on this... it is driving us crazy- especially when we stall right in the middle of a turn and almost cause an accident!
Thank you!
Paul

Answer
It's time to check to see if the VSS is actually delivering the speed signal it should.  You'll need a shop with a scope for that.

If it's not, look for a mechanical issue in the transfer case or a defective part.

If it is, look to wiring or ecu troubles.