the other day i was under the car putting some locktite on the driveshaft bolts and i got to thinking if the previous owner ever checked the rear end fluid. so i opened it up and there was none and the magnetic plug had about 1/4 inch of metalic sludge on it. i wiped it off with my fingers and held it about an inch away from the mufflers and it lifter off my finger and stuck to the muffler. i filled it up with 80w90 and now i can hear i whining noise when i am going slow over the dirt driveway bumps and sometimes going down the road at about 70 it really gets loud and lasts for a few seconds and goes away. it is coming from the back, so i thought it was the E brake sticking so i pulled it barely while going 70 and it did not make a noise. i slammed it up and down to get it unstuck but nothing happened. so i wannna know how and why it just started after putting oil in it. how can i stop it. 95 5 spd