My son noticed a strange noise comming from the rear of his truck today.
I would describe it as a humming noise. Its present at most all speeds. Very noticable at lower speeds as well. Applying the brakes made no change.
This is a 1997 f150 2 wheel drive with a 5.4 L automatic.
I'm guessing its the rear end. I'm gonna pull the plug and see if the gear oil is full.
Could it possible be the u joints? Not getting any clunks. Oh yea, there are 234k miles on the truck. It still runs real strong. It was a company vehicle when we bought it. They kept it up real good. Seems like they spared no expense in the upkeep.
Looking for any input. thanks..

 

Make sure the pinion shaft nut is tight. Just a wrench or socket to test, if loose a whole other deal.....

 

I pulled the plug and looked at the gear lube. A little runny in my opinion. Not to dark.No crap in the excess that came out. It was filled about 3 oz over the plug. I'm thinking that must have been the original?? Don't know how that could have been done unless it was before the axle was installed.
I also put the rear end up on jackstands and put the truck in gear. It was hard to pinpoint the noise.
Actually sounded loudest in the center of the driveshaft.
No play in the u-joints. I didn't see any grease fittings on them. I am assuming they are the originals.
Thats what I've got so far.
Isn't it true that your u-joints can go bad without actually seeing any indications? At least in the beginning.
This humming noise just became noticable today.
Still need some answers. Help!!!!

 

It could be the pinion bearings.My 97 did the same thing and I had to have the differential rebuilt.$700 plus tax!