Q: I noticed a howling sound coming from my right rear wheel about 5,000 miles ago. i tried to find to source of the noise as best i could. i found that i had a leaking gasket where the drive shaft enters the differential housing. I replaced that gasket and added more gear oil (a little more than 1 quart). the howling sound persisted and has gotten louder. it's first noticeable at about 30 mph and loudest at around 55 mph. at 65 to 70 mph it's not as loud but still quite noticeable. What do you think is the cause? could it just be an axle bearing, or am i looking at needing to either rebuild or replace the rear axle and differential?
A: It could be either one. The axle bearing is the most likely cause based on your description but the rear diff., since it was low on oil may be affected.
You should take it to a dealer or someone that specializes in the Toyota product.