Driveshaft noise??

[ron4pres]

I am hearing a loud humming while at speed (above 50mph) and it sounds like it is coming from beneath/behind the cab.
The noise occurs under load and in 4/5 gear.  Since the noise is usually at 50+, testing in 3rd gear gets more engine noise and it is harder to hear if the "hum" is still there.  It sounds like loud tire noise, except that when I let off the throttle, it disappears.
Everything is lubed and I have checked the rear diff fluid.
I read another post about loose pinion gears, how could I check them out on my truck?
Thanks for your help,
Ron

[WHITE_TRASH]

park your truck in neutral and set the parking brake.  get underneath your truck and try and twist your driveline if you get more then about 1/2 inch of turn and or if the pinion flange moves in & out your pinion is loose.  To remedy the situation you need to take off your drivelind and torpue the flange down to 95? foot pounds.  
Good luck
WT

[84runner]

So did you figure out if the pinion was loose

[mr4x42u]

sounds like its too late..Bet the pinion bearing is bad..Once they hummmmm there done!The on and off the throttle noise is what they do when there bad..

[ron4pres]

Well, about the pinion...
So we finally got some snow on the Eastern Shore of MD and I went out with my neighbor whom I have been friends with since we were 16...
He is always giving me grief for sticking with my "old and busted" and he says his F150 is so much better...
Well, he got stuck in what we will call Lake Delmarva...
About 28-29 inches deep.  So bad, his rear wheels were turning, but not hitting anything.
Anyway, after pulling him out, I must have really jarred something because I lost a UBolt on the rear axle...
Long story short, I have aligned my truck and ordered the Downey LSD with all 4 bearings... If there is still a problem, it won't be there...
Thanks for the advice everyone.

[84runner]

Whats your buddys opinion now about your yota?

[donkeykong]

Nothing shuts them up like being pulled out by a "4 Banger"

[84runner]