I have a 2001 supercrew 4x4. I have notice lately there's a loud roaring sound coming from under the truck. It sounds like gears meshing. I checked and the 4x4 switch isn't ingaged and no lights on the dash indicating so. Does this mean that maybe the oil in the transfer case is low or needs changing or something else?

 

Have you been driving around Africa at all lately? These trucks had an issue with Lions getting stuck in the undercarriage when they were trying to stay out of the sun. Jump under the truck and take a look. He probably is just trying to get out, might not be the issue, but it's worth a quick look for sure. Just remember lions are a wild animal, so treat them with the respect they deserve.

 

Could be your rear diff, when my pinion was on it's last leg it sounded like I just bought brand new mud tires lol. I'd get the differential checked, also crawl under the truck and see if you are leaking fluid where the drive shaft goes into the trans. I am leaking pretty bad there.


I didn't want to crawl under the truck this morning but this pic shows a little splatter with the front par of the shaft wet and the under carriage being soaked.

 

Is the sound constant with no change in tone with rpm changes? Does the sound go away when coasting and in neutral?

 

When I take my foot off of the accelerator to stop for traffic or for a stop sign it gradually (winds down) then upon acceleration it winds back up so to speak. I have not tried it in neutral.

 

Gears are worn in the differential. How many miles are on the truck? Which engine?

 

It has 170.000...4.6 v8. Still makes noise even in neutral.

 

I had a wheel bearing chewing its way through the axle that made a very nasty growling sound.
Put the rear up on jack stands then get your ear under there and listen while someone runs it a little.