Driveline Hum with VIDEO!!

[lone_star_dsl]

Ever since I bought the truck (May 05 with 42,000 on it) it has had a very slight driveline hum. It has stayed about the same until a few weeks ago.

The hum is so annoying and loud that the truck is almost undriveable.

It's loudest between 58 & 62 mph although it starts around 30. It only hums when I am on the throttle either accelerating or maintaining speed. I have tried it with the transfer case in 4wd with no change.

The u-joint closest to the rear differential was replaced about two years ago, the center bearing was replaced about a year ago and the rear end was rebuilt a few months ago. Other than that, the rest of the driveline still has factory parts. Replacing these parts has never caused the hum to go away completely.

I'm not getting any weird vibrations or anything when the hum is occurring. The hum sounds like it's coming from directly beneath the cab.

Here is the video I took of the sound: 2002 Ford F-350 SRW Powerstroke Driveline Hum - YouTube

Let me know what you guys think. I really don't want to throw money at it blindly.

Thanks

 

[Tail_Gunner]

It only hums when I am on the throttle either accelerating or maintaining speed.

1 vote for rear end gears.

A few years back I had a noise like you're describing. I suspected rear end noise and had the shop check it out. Sure enough, the gears were worn. (Might have had something to do with 250K+ of towing a 8,000lbs trailer.)

New ring + pinion gears= No more noise.

 

[Dogman]

lone_star,
I'm thinking a bearing in transfer case is running dry. I had a noise like that in my jeep and the pump that oils the bearing in the T-case was missing the pick up tube, it fell off the pump. Could be the chain in the case too.

 

[BIG JOE]

I'd Second TG's vote.

With the years of Snowplow operations.. Traction issues could have worn down the Ring & Pinion, Bearings and Axle Splines ?

Joe

Dogman makes good points too.

 

[lone_star_dsl]

lone_star,
I'm thinking a bearing in transfer case is running dry. I had a noise like that in my jeep and the pump that oils the bearing in the T-case was missing the pick up tube, it fell off the pump. Could be the chain in the case too.

Sounds legitimate. I'll check on that this weekend. Don't you think there would be a change in the noise when I engage 4wd?

I'd Second TG's vote.

With the years of Snowplow operations.. Traction issues could have worn down the Ring & Pinion, Bearings and Axle Splines ?

Joe

Dogman makes good points too.

It's got a new diff in it as of a few months ago. Since then the truck has seen about 3k miles of towing (12k lb gooseneck) and about 3k of empty driving.

 

[BIG JOE]

It's got a new diff in it as of a few months ago. Since then the truck has seen about 3k miles of towing (12k lb gooseneck) and about 3k of empty driving.[/QUOTE]

Hmmm. Takes care of that then. If it's not the T-case, then maybe the exhaust system ? Something rubbing/touching when the engine is torqued over, under certain loads ?

 

[lone_star_dsl]

If I have time, I'm going to pull the rear driveshafts(s) this weekend and take it for a spin in front wheel drive to see if that eliminates the problem. Hopefully the problem will narrow itself down.

I don't know why I didn't think of that first.

 

[JLDickmon]

that sounds like a planetary whine to me...

 

[lone_star_dsl]

that sounds like a planetary whine to me...

Are there planetary gears in the transfer case? I'm sure there are some in the transmission.

I took the truck in for an oil change today and they checked both diffs, the tranny and transfer case. Everything looked ok with the exception of the rear end. It looked filthy.

Should the rear end lube be changed at a certain mileage after a rebuild?

 

[lone_star_dsl]

**UPDATE**

I took it by the shop that did the rear end rebuild to have them take a look at it. They did a test drive and put it on the lift. The shop owner said the coast side of the gears was worn extremely bad.

The good news is that I am getting a new rear end, the bad news is that I am without my truck for the week.

The shop owner said that this is only the second rear end to come back and that the shop has done over 400 of them. I believe him too. He has been in business for over 30 years. I'm just glad he's standing behind the work.