Pass lock 2003 Chevy Tahoe - 2003 Chevrolet Tahoe

SOURCE: 2003 chevy tahoe front rear end fluid

i think what you are talking about is the front differential. you will wanna put gear oil in it. the correct weight would be found in your manual.

SOURCE: 2003 Chevy Tahoe

Its probably the temperature actuator located in the right rear interior

SOURCE: Where is the oil sending unit located on a 2003 Chevy Tahoe 5.3 engine

its in the block behind intake manifold .

SOURCE: power locks for rear doors and hatch not unlocking

you have two relays on the interior fuse block one for locking and one for unlocking. Swap them and see if the problem is now such that they will not lock. If so you have your answer.

SOURCE: 2003 Chevy Tahoe. Driver's side power window

check releys and wires in door jam 1 might be broken failing that u need a new switch