Advice Please

2002 TRD 4x4 EXT CAB AT 3.4 195,000. Most OME PARTS.
Changed All Fluids. Rear was BLACK! Replaced ujoints & rear carrier support. Rear moan (RLocker off) in drive and neutral, ESPECIALLY WHEN COASTING and foot off the gas. NO Leaks.Mech says pinion bearing?
Rear on stands, listening w long Flat scrwdrvr. In Dr I can stop pass tire but Dr side won’t stop. Dr side is making a low dull whup whup whup whup. PLEASE tell me how to diagnosis this sound. It’s starting to get bad. Wheels have no play.

 

Is the whup whup sound rotational?

 

The fluid could be black because its just never been changed, I'd say this is unfortunately typical. You just don't want any metal in it. Do you hear the whup noise from the wheel area or the center of the diff area?

 

A howl while coasting is certainly a sign of a bad pinion bearing.
The whup, whup, could be a number of things. Depends on where you hear the noise the loudest?

 

I drained it and filled it with the best

In all due respect is there another way to hear a sound unless the wheel is spinning? If you mean counter clockwise while in drive then yes.

 

While in drive up on jackstands and giving a little gas. The driver’s side rear makes a dull low whup whup consistent low sound.

 

Where at?
On the axle tube?
Closer to the wheel or the center differential?

 

Great question, do you know of the best way to make a homemade stethoscope?

 

I changed the differential oil with the best money could buy with spec about 8,000 mls ago.

 

About 8,000 miles ago I drained all that black oil and replaced with the best money could buy according to spec.

 

The long flat screw driver like you were using is about as good as home-made as it gets....
Wooded broom handles work too. For hard to reach places.

 

The vibration is coming through the floor board and steering wheel.

 

When up on jack stands

 

I replaced it with the best money could buy per spec

 

Pretty sure Spicer was the OEM supplier for u-joints and carrier.
But I don NOT think that either of those are your issue.

 

No sir, I replaced them with Koyo or high end Spicers.

 

Now guys listening to the rear remember with a long flathead screwdriver. The front of the third member sounded a little grinding, certainly wasn’t smooth.

 

That's where the pinion bearing is at....
Do you have any play in the flange where the driveshaft bolts to the rear diff?
Grab it and push up/ pull down on it.

 

$8 BFXM Car Mechanic Stethoscope, Automotive Stethoscope Engine Diagnostic Tool, Automotive Tools Universal for Car Truck SUV Motorcycle RV

https://www.amazon.com/dp/B0D91VMQR6

 

Thank you!