Hi:

I just bought a 94 Disco and I'm in the process of servicing. I've been having a problem going into 3rd gear. I get this jerking motion. The LR shop tells me its the TPS sensor. They unplugged it until I can get a new one, but I'm still having the problem. The LR shop ran a complete diagnostic and the transmission checked out fine. Please advise!!

 

Sounds to me like you have a tire or tires out of round.
I am having same symptoms with my truck. I just do not want to fork out the money for a new set right now.
Conrad