Volvo 245 D24 problems with car I just got

[Echo1975]

I just bought myself a 245 with a NA D24 engine and manual 4 speed with OD, I am having some issues with it and I hope you guys can help me.

My first minor issue is that, whenever you move the shifter even slightly with OD on, it shifts back into 4th. It's very sensitive for some reason and I wonder if that's normal.

The second issue is when the engine gets hot it sometimes makes a quiet high pitch whine that increases when you floor it and then goes away for a couple of minutes when you let off the throttle

The third small issue is that the speed gauge meter jumps around quite a bit.

I have welded almost all the rust holes and done a lot of work on it already and hope I can solve these small problems too.

The car is very fun to drive