E350 - Droning Noise (from rear?) at deceleration

[E-350]

Hey guys

I have a "droning noise" problem I'd like to get some input and will try to provide the info I have as systematic and detailed as possible :-D

Problem description:
- Droning/ dump noise in the van cabin as if you would drive on "micro washboard"
- feels like whole cabin "resonates"

- Situation 1: accelerating at speeds >65/70
- Situation 2: stable speed above 65-ish (at these high speed I have the feeling I can somewhat "feel" some jiggling from the drive train beside only having the droning)
- Situation 3: when decelerating between like 60 down to 35/40-ish
- Situation 4: decelerating from 75-ish down to 65-ish
- Cruise control on: level at 65 = no noise, uphill at 65 = noise starts, downhill at 65 = noise louder than uphill

- not depending on the gear (overdrive on/off doesn't change anything)
- not depending on rpm
- not depending on running straight/ left or right curve
- not depending on cruise control or not
- no vibration in steering wheel
- somewhat depending on speed (it's getting louder the faster you get, but frequency is not significantly changing)
- I have the feeling it comes from the back: I have plywood screwed down on the floor and the more I sit above the rear axle on the floor the more I can feel the vibrations and the fact that I don't feel vibration in the steering wheel
- speed range >65-ish: no change between decelerating and accelerating. so decel.ling and then accelerating doesn't really change the noise
- speed range 35-55-ish: noise while decelerating (foot off pedal), but gone immediately once hitting the pedal again

--> so all in all I'd say it happens when the whole driveline is fully unloaded and when I'm at high speed
--> I don't think it the trans as it's not rpm related



System Set up (installed by 4WP):
- ARB Air Locker incl. new Yukon 4.56 gearing has been installed ~2.000 miles ago (it didn't start with the rebuilt, but just some 100 miles ago)
- with the locker new axle shafts have been installed
- new crush sleeve should have been installed (as I waited for more than a week for this part, so they ordered it and charged me for it)
- 35's are ~2.000 miles/ a few months old



What I already did/ what I think:
- rear transfer housing leaked and I found the bushing is also bad --> both replaced, no leak, no change to vibrations, no more play of the drive shaft at the trans housing

- u joints seem well, couldn't find play

- Pinion seal/ differential doesn't show a leak

- As I still had to do it I drained the Diff Oil: no metal shavings found, can't see any strong wear on the teeth beside that they start to show the first initial wear signs where they're touching each other (looks absolutely normal to me). What I found were quite some bubbles after 15min sit time, but that seems to be somewhat normal?! Oil used: Lucas 85W-140 SAE GL-5
If you want I could take a picture of the diff internals/ teeth.

- played with tire pressures front and back (from 40-65psi): doesn't change anything

- I don't think something simply got loose: exhaust is fine, springs/ shocks are tightened up, heat covers are all snugged up, front bearings are fine, ...



Possible root causes and priority I would move on:
1. Wheel Bearings and Axle Shafts
Take axle shafts out (as diff is currently empty) and confirm wheel bearings/ shafts are ok
--> don't really think it's the wheel bearings as I don't hear ANYTHING <30mph and there's no difference running straight/ curves. I had some front and rear bearings going bad on different vehicles and that sounds different... But hey: best moment to check

2. Pinion bearing/ crush sleeve
This seems to be a common topic and somewhat makes sense that after ~1.500miles with the new setup and possibly wrong installation this would show up. Pinion adjustment seems to be a typical problem for vibration when not under load?!?
Even if the torque on the pinion is correct, I still haven't ruled out that they tightened it down too much and went back to normal. Would mean the sleeve could be bad. But would it cause leakage as well?!?

3. ???
That's where you come in :-D

"OT" Idea: Body Mounts
Assuming there is some vibration it could also mean they body mounts don't work properly anymore (2006, 270k miles...). But that wouldn't really explain the symptoms... so must probably to be skipped...



Eventually my questions:
- Which items I already ruled out should I re-confirm?
- What do you think it is?
- Anything easy/ quick I can check before touching the pinion?
- Am I off track and you think it's something completely else?

[desertsherpa]

Driveshaft balance / U joints?
Can you pull the rear driveshaft and take a spin (if its a slip yoke, maybe not)?

Balancing of rear brakes / drums? My rear disc brakes have an internal drum for the parking brake.

Rotate tires and see if the vibration moves ? Tire out of balance?

Pinion crush sleeve seems possible due to the supposed angle change (up vs down).

[loper]

My first thought is rear end set up (pinion bearings, crush sleeve, lash).
Second thought is greasing the u-joints.
Rotating and balancing the tires might do it, or at least help you eliminate some variables.

[Lilnuts2]

How many miles on the ujoints, I know you said you looked at them??
is your your rear driveshaft a "slip fit" style?
I also second removing the rear driveshaft and going for a test drive.

It seems interesting your "whine" came up within 2,000 miles of having the rear end opened up

[E-350]

I think I forgot to mention one very important thing: I'm a RWD'er. So disconnecting the driveshaft makes me stop all the way :-P

U joints:
I got the van with 250k miles and I assume they've never been changed. I put it on my todo list. not too expensive and fairly quickly done.

Driveshaft balance:
hhmmm... why now and why not between 55-60-ish... I can see where they welded another piece of metal on and don't see any sign that something "got lost"...

Drum brakes:
ha! you got me! A thing I wanted to adjust for months. They're so loose they can't keep me from driving off :-D so I assume there is enough play :-D

Tire Rotation:
yep, good idea. didn't test it yet.

So all in all and for now it looks like:
1. put new ujoints in. For the sake of completeness and "just because".
2. Take a look at the axle shafts and see if there's something wrong.
3. If not proceed with filling up the diff with oil and drive to see whether or not the ujoints were the root cause.
4. Then tire rotation.

Afterwards I would have ruled out more or less everything, so it would only be the pinion left...

Could I test/ check anything on the pinion BEFORE I fill up the diff? I saw some stuff with some kind of paint on the gears to see how they "touch each other"...

[REF]

Wouldn’t dismiss it as a possible drone from the exhaust touching or hitting the frame or a hangar, then transferring the sound through the floor. Obviously things expand when warmed up, gas or diesel?
I’m running a 4” exhaust on my 7.3, there’s very tight tolerances between the doghouse pinch weld and the exhaust, things got shifted around slightly with some work I had done and when warmed up, the exhaust made contact with the edge of the doghouse opening and made a racket.

[E-350]

Couldn‘t I just pull the axles shafts out, driveshaft off and „feel“ is the bearing is bad or has some play? Without tires connected and the driveshaft it should be turnable fairly eas right?

[E-350]

Here‘s a pic from the „inside“
Not really middle, but I also think not too bad…?!

[carringb]

I’d put my money in I-joints as well. Even without play, they can form small ridges that you can feel when you take it out and move it by hand (and you can see them).

Pinion gear or backlash should only present those symptoms when decelerating..

[E-350]

Just thinking…

When I replaced my extension housing bushing I could slightly feel some play. Not a whole lot, but a bit.

In case this would need to be without wiggling, it could also transfer vibrations and be the root cause… due to the lift the yoke slipped out further than normal and showed slight wear. Combing less overlap in the slip yoke area + min play of a few 100um…

Get a new yoke and/ or tighter bushing…

Man! I go crazy ����

Also just checked the u joints again. There‘s no play at all and the noise is too substantial for these small bearings… just a gut feeling.