I had to have my transmission replaced after i lent my car to my dad who then hit a massive pothole and destroyed my transmission along with tire and rim. Got my car back and while driving home, I noticed my temperature gauge didn’t move. Got home, parked the car and let it run and no movement from the gauge at all. Unfortunately, I retrieved my car shortly before the shop closed so I can’t call them until tomorrow but does anyone know what this could possibly be?
Sometimes a large wiring harness has to be unplugged from certain engine sensors/solenoids on the transmission in order to remove the transmission.
Just ask them to check if everything was plugged back in if such a harness had to be unplugged.
Simplest explanation is the wire to the (or one of the two) temp sensors was not reconnected after the transmission was installed.
More serious would be the radiator/ cooling system was not refilled. That could mean serious overheating and engine damage. Without coolant circulating past it, a temp sensor senses nothing. Check that before running it again.