Hey Everyone!!

I am a newer owner of a 1999 Disco 1 that was kept in excellent condition,120k miles on it right now. I have an issue of it slipping out of gears/not shifting into gears while driving. Main issue right now is it is slipping out of 4th gear to 3rd around 45mph, it will try to start off the line in 2nd gear, and it won't register its in reverse at times. Thing is, once it figures out which gear it needs to be in, it'll drive fine after it's little temper tantrum. I have been routinely checking all fluid levels since I got her and have noticed no leaks in transmission fluid. I also just got her back from one of the most reputable land rover mechanics in my state and he couldn't find any problems. He couldn't replicate the gears slipping and mechanically everything looks sound. I had my dad drive it and he noticed it acting weird too, suggested that it was an electrical switch that is faulty.

Any advice??

 

Transmission, ZF4HP22, doesn't use any electrical or vacuum signals from the engine, ecu, or otherwise.
I'd check a couple simple things first. Shift linkage and the kick-down cable. Both are covered in the RAVE. You can find links to it HERE