Okay get this...

When I first got my truck the rear end would whine around 75 mph (yeah I know I speed sometimes), But it would only do it at this specific speed in O/D. Now, around town, I drive with O/D off and it just started to whine in third gear around 40 mph. I can tell it is the rear because it only whines when I give it throttle and stops when I let it coast.

I have a 3.31 behind a 5.4... I only have about 5000 miles on the odometer.

Maybe I should just take it back to my dealer, but darn it if they are a pain to deal with and the fact that I would have to pay for a rental...

At least it goes partially away with the radio turned up...

 

me too man . . mine is between 62 and 65 mph . . same symptoms. disappears if you let out of the throttle. definitely the rear end gears. mine is a very light whine and doesn't really bother me too much. i don't believe that it is any kind of a reliability problem. i've had other vehicles that have done this, including one bmw. never turned into a repair. but if it is loud enough, i'm sure it would quickly become very annoying.

 

Guys, that whine could be the bearings in the rear end. I have been trying to find a vibration in my truck ('94) and I am starting to look at a new set of bearings and a new LS kit as well. The Service Manager was telling me about some of the bearings along with synthetic oil. He was saying that some of the bearings in the rear ends date back to the '70's. That is how long that they have been using these bearings, it is not all of them but some of them. He also said that if you compare my rear end to your's that they have had far less problems with my rear end compared to your rear end. It has something to do with the different types of oil between mine and yours. You guys have synthetic and I don't (85W90 or something like that) with the friction modifier in it. They had one truck (newer style) that they changed the oil in and then changed it again 10,000 kms later and BOTH times it was milky. He wonders if it is when the bearings heat up and start to cool that the oil can't handle any condensation that happens. Then the oil becomes milky and then you get the whines from the bearings wearing out. Try this sometime and see what happens. Put the truck up on a floor jack via the differential pumpkin and have someone slowly speed the truck up to 50 km/hr. The whine should come through the floor jack and make an even louder version of the noise that you hear. I haven't done it to mine yet but I might just spend the cash and replace everything just to eliminate this issue. Hope this helps.

Have Fun & Keep on Truckin'
Dean

 

There is no way I could stand a whine in a new truck. If your F150 is still under warranty, which I presume it is, I would find another reputable dealer and get the problem fixed immediately.

Also, take a close look at the pinion seal (where the drive shaft yoke hooks up), and check for any oil leakage there. Check at the wheel ends (on axle housing) for leaks too.

Any oil leakage for a short period of time could indicate You need more than bearings. The ring & pinion may be toasted.

As for "milky" looking diff. lube; good chance axle vent tube (rubber hose on left rear/top of axle tube) is letting outside water contamination into the diff. housing. Good luck guys, Gearman

 

if the noise gets louder with speed then its brgs , but if the noise will go away either acc. or slowing down ...its the gears depending on whether its making noise on the face or the back of the ring and pinion set ..... have ford replace the entire setup . gears and brgs ....