And this morning I have no reverse or drive again...

 

Unplug the TCu for a minute or two. Then plug it back in.

 

Went to move rover to mess with TCM. It went right into reverse...
I still pulled the TCM. It is dry and clean. I put some dielectric grease in the "holes" on the plug to encourage better contact. All is working at this time. We will see what later brings.

 

sense 4th gear is working the way it should I will close this thread and start another for the trans not engaging. Thank you all who helped and made suggestions on this thread.

 

Could be XYZ.
When going along try to push the handle just a bit toward the "N" from D.
Just a tad. See if it goes into 4th.

If the brakes are dragging and there is LOAD on the drive train it will not go into 4th or Torque convertor lockup mode.

Lastly, the clutches are driven by solenoids. One of those could be sticky or the wiring is not providing enough current.

Make sure you put the ground strap between the driver;s side firewall and the cylinder head back on.

Make sure the battery is fresh,

Just a volt more in your system or more current to the transmission may just pull that clutch in and you'll get 4th if that is the problem.

 

On Discovery I there was a speed sensor.
On Discovery 2 there was a speed sensor which went into the transmission.
if that was off you would get trouble too.
If there is a cable from the accelerator to the transmission make sure that is adjusted correctly.

Don't remember if the ZF on the Discovery still has that cable but if it does then that
could do it too