904 trans mysterious ticking sound and introduction

This morning early and with everything still very cold the trans shifted properly at low speed from 1st to 2nd. Just the once, it was aprox 25F outside. Could the oil being thick have something to do with my prob.?

I have the car on a lift as I'm working on the rear quarters so I want to check the shift linkage, how does it work with relation to pressure? Further back at the trans towards the rear of the vehicle is more or less pressure? And is more pressure delayed shifting?

TIA
David