hi guys im new to the board,, here is my problem, i got a 79
f150 and every time i get to 50+ the rear end hums . im stumped
hopefully some one can help..

Change the fluid in your rear differential, have you checked it? It's an older model truck, that just might be the problem.

If you have checked the fluid and the fluid is good; or just flush the system and if the humming continues then you must replace the bearrngs in the rear end and make sure you inspect the pinion.

Providing fluid's in good condition, humming is usually gears meshing. Bearings make a far more horrible noise usually, like a thump almost and they're almost always a rotational noise. We see a lot of new rear ends humming and put ring and pinion sets in. In reality, though, as long as you can take the noise, you're probably alright. Good luck with it.