one works the other turns off when i put my brakes on then when i release them it comes on again ive looked at the wires put new ones in put that elec greese in the tube i dont know its driveing me crazy this is on a 76 ford 250

 

Try adding a new ground wire, just us a jumper wire, to see if it helps.

The tail light might be finding its ground thru the brake light filaments.

 

Yep, sounds like a ground problem. It could be the connection in the socket from the brass part of the bulb to the little tang in the socket. It could be the connection inside the socket that goes to the wire coming out of the socket(I have had this happen to me twice), or it could be where the ground wire actually bolts to the bed.

 

the ground wire on the harness usually is grounded to the rear crossmember near the left frame rail