Most Likely Culprit for Whine/Hum

Joined
Jul 21, 2013
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Location
D/FW Metroplex
I'm trying to help my brother diagnose (via txt) a humming/whining noise his truck is making. We cannot agree on what the most likely culprit is, so I'm looking for some 2nd opinions.

Pertinent Info:

1) 2004 1 ton Dodge dually megacab longbed turbo Diesel with 321K miles on the clock.

2) automatic transmission was rebuilt within the last year or two.

3) carrier bearing and rear shaft's u-joints replaced shortly after trans rebuild.

4) rear diff gear oil changed for the first time a couple days before this behavior began.

5) when speed is over 45 mph or so and the trans is in gear, there is a steady hum/whine from under vehicle.

6) letting off the gas does not deter the sound, but shifting into neutral does cause it to go away...until it's put back into drive again, then it resumes.

He believes it is the carrier bearing, and I believe it is the rear-end. What do y'all think?
 
The Diff was drained. Now there is a whine. Was Diff refilled? What with? over filled and foaming? I've screwed up enough times to know where to look when there is a problem with something I worked on
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The gear oil drain and fill on the rear diff was done by a quicky lube place where he lives (Abilene), so whether or not the correct fluid was used is anyone's guess.

I'd like to think they knew what they were doing and used the right stuff, and used the correct amount of it, but it's definitely not a given that they did...
 
Originally Posted by sloinker
Only under acceleration above 45 mph? Sounds like a pinion bearing.

No, about 45 mph is when it gets loud enough to be heard, but it does not have to be accelerating.

Accelerating, you hear it,

let off the gas pedal, you still hear it,

shift into neutral, and it goes away,

shift back into drive (without hitting gas pedal) and it starts right back up
 
Everything is still spinning in neutral, driveshaft /‘d rear end included. Carrier bearings will make noise as long as the truck is moving. Same for the rear end. A backlash or improper gear pattern will cause noise on acceleration.

It is worth inspecting the rear end but I think you have a bearing or gear set in the transmission that is causing your problem. Although the D+F on the differential and then you say it started is a little strange..
 
Last edited:
Originally Posted by 4WD
Did they mention anything about the old oil looking pretty rough ?


I can't say, it's my brother's truck and he's the one that had it done. It's currently sitting on some ranch land while he finds a trailer to get it back home and have someone look at it. I've just been trying to remote diagnose a little so he'll know what's coming in terms of trouble/cost of repair.
 
Originally Posted by RhondaHonda
I'd start with the diff. Drain and fill with correct amount of fluid.


Yes .

Is it a limited slip diff ? If so , it needs a different type of gear lube .

Purchase a diff cover with a drain plug & a gasket . If it uses sealant , in stead of a gasket , use what ever MOPAR recommends . Do not over fill .

Look for leaks while you are at it .
 
Originally Posted by WyrTwister
Originally Posted by RhondaHonda
I'd start with the diff. Drain and fill with correct amount of fluid.


Yes .

Is it a limited slip diff ? If so , it needs a different type of gear lube .

Purchase a diff cover with a drain plug & a gasket . If it uses sealant , in stead of a gasket , use what ever MOPAR recommends . Do not over fill .

Look for leaks while you are at it .


I got my hands full with The Bacon Hauler's preventative maintenance and periodic break/fixes. Anything that's done to the Dodge truck in question will likely be done by some independent shop in Abilene...or another quicky lube
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Originally Posted by clinebarger
Turn O/D off & see if the whine is still present.


I saw that procedure mentioned somewhere while I was doing some research on those trucks and driveline issues they have. What is the implication of the behavior changes/goes away with O/D turned off? Something to do with the transmission itself I'm assuming...
 
Originally Posted by The_Nuke
6) letting off the gas does not deter the sound, but shifting into neutral does cause it to go away...until it's put back into drive again, then it resumes.

This tells me the noise is coming from the transmission.
 
Maybe … but going back in gear returns the load on the whole system, rear end included.
This is not one to be easily solved here … but rather up on a lift …
 
Well as luck would have it, I just got word there is a water leak somewhere between the house and the well, so I get to spend 5 hours driving down there to go find it and fix it. I'll give the truck a whirl while I'm down there and see if anything extra jumps out at me, especially the O/D trick.

Stay tuned...
 
Whelp, it would appear the problem lies within the transmission or possibly TC (I am not familiar enough with these trucks' trans/TC setup to know for sure). The noise is barely audible when the engine is cold, sounding like a set of mud grip tires, but only when you get to 55 mph+.

But once the engine (and ostensibly the trans fluid) warms up to operating temp, the noise becomes noticeable at 25 mph, and it gets loud enough to worry you into slowing down at 55+ mph.

The kicker: engaging the Tow/Haul button on the end of the shifter (and turning off the O/D gear I believe) stops the noise if it's currently audible, and it prevents the noise at any mph if already engaged.
 
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