My father's 97 corolla with the 3 speed transmission recently develop a whine. Drove it to my usual mechanic where he suggested to try change both the oil in the tranny and the differential to see if it helps. (this transaxle has a seperate differential drain plug). The tranny was drained first and the fluid looked and smelled okay. Then he open up the drain plug of the differential - I could not believe my eyes that only a few drops drained out, it was almost dry !
My question to the group is : how can the differential run dry without my father noticing any leak ? I am very sure there is no stain on my father's drive way, where he park his car 99% of the time. Where would have the oil gone ? I was thinking of the drive axle oil seal but my mechanic said it looked okay.
Last time the car had the transmission and differential oil change was about one year ago at the same shop. I am thinking if my mechanic forgot to fill the differential during the last change, how could the unit went one year a few thousand miles without blowing up ? Actually according to my dad the whine only developed in the last few days.
Any suggestion about what could have caused the leak ?