I have a very rusty 89 range rover, the shift **** popped off, the shifter moves but don't feel like its locking into anything, its stuck in high gear, which is fine. I am wondering what could be the issue, I would like to get it working even if I don't use it.

 

I'm pretty sure that even in your model year there was a solenoid (FTC2890) that inhibits unintentional shifting between hi and lo. You may have a bad connection or a bad solenoid. Or, if your truck has lived in a rough climate, it could be frozen from years of not being used.