Will Chatham

I bought a 2006 Ford F150 with the 4.6. Shortly after it developed a drive-line roar and I discovered the rear diff had no fluid in it. I payed to have it rebuilt and the problem still exists. the mechanic seems to think I have a bent frame as the rear end has been in before. I nor the mechanic was able to find any stress points or visible bends in the frame though. My theory is the split driveshaft bearing may be bad. I need a reliable vehicle and I really can't deal with a bent frame, any input would be welcome.

greasyknuckles

does it have a 2 piece driveshaft? or a center support bearing? A quick listen
with a stethoscope while the truck is in the air running in gear will determine
that. 5 minute test. if your guy cant determine if that bearing has failed it's
time for a new guy

Toshbar

What does 'rebuilt' mean? All the bearings or just the carrier bearings? Were the ring and pinion replaced? Everything but the carrier? How about the wheel bearings?

If the rear diff had no fluid, I would not look further until everything in there had been replaced or looked at closely.

gmb13

Easiest way to check the carrier bearing is to pull the back shaft off and run it up 60 on the speedometer. if you hear a howl the bearing is bad since the rear end isn't even turning.

Toshbar

The carrier is inside the rear end.

Will Chatham

Okay so a few things: 1. I thought the carrier bearing was where the split drive shaft bearing was? 2. I Have a split drive shaft and I checked the bearing where the split is as I thought it was bad, but it's 100 % fine. 3. I had just the differential bearings and seals replaced (the gears were fine), I did NOT have the axle bearings replaced as they appeared to be fine. 4. I checked the axle bearings myself and they didn't appear to have any wobble or play in them. So my question is, what could it be still?

Will Chatham

ALSO: The roar presents around 30 mph and is loudest at about 50 mph, it tapers off around 55 mph and then gets loud again around 65 mph. I'm fairly new to differentials and all so please just be patient with me. lol

greasyknuckles

some people including myself at times call the driveshaft center support bearing, a
carrier bearing. As far as bent frame, that would cause a vibration more than
anything. Assuming when you tested the bearings you used either a stethoscope or
a screwdriver held up to your ear pressed against the area in question. just checking
for play doesn't work at the bearing race could have pitting and that will cause a noise and won't necessarily have play. you have to have it up in the air with someone
in it spinning the tires watching the speedo to keep it in that range. IS this 4x4? what
type of tires? make sure the fan clutch is not seized. And 1 more thing, if the ring and
pinion was not replaced or if pinion depth, backlash and bearing preload are not set
correctly you can have a noise also.

gmb13

It may be a regional thing, but around here the carrier bearing is the bearing that carries the drive shaft when there are 2 or more sections.
The bearings in the differential are pinion & side bearings.
How did you check the drive shaft bearing? It may feel tight but still make noise.
I would get the truck up on stands spin it up and see if you can narrow it down.