High pitch noise between 50mph-60mph. Lots of searching and troubleshooting done with no luck.

[93z]

Hello Mud I have a tough one,

I need help identifying the source of a noise. It is a loud high pitch whine between 50-60 mph. It sounds like a mid-pitch tuning fork. It has been around for over a year. I have taken it on 1,000-mile trips and beat on it in the woods. Passengers have said it is coming from the center of the truck and it is not as loud when sticking your head out the window. It sounds like coming from the rear to me (loudest to my ears near the b-pillar). I have done plenty of forum searching but nothing posted is quite the same as my issue.

Cruiser Details –

• 1993 US FZJ80L mostly base-lined, not triple locked, 105,xxx miles (bought at 93k), fresh head gasket, PIAR/EGR/Cats removed, CDL switch. 2” TJM lift with radius bushings. Rear Spartan locker, 33/12.5/17, no transfer case mods, VC in place, fresh paint. Love this thing.

Issue Details –

• Noise is speed dependent. It is loud between 50-60 mph. Above and below that window there is no noise.
• On and off throttle make do difference.
• I can change gears and makes no difference so not RPM dependent.
• I can pull the transfer case into neutral at speed and the noise is still there.
• I can pull the rear e-break or press on the break peddle and the noise is still there.
• Pulled the front driveshaft, drive hub flanges, and locked the center diff. no change.
• Pulled the rear driveshaft, rear axles, and locked the center diff. no change.
• Pulled both shafts and got up to speed in my garage. No noise.

Things I have tried (not in chronological order) or done for other reasons that I hoped would help –

• Rebuilt the front axle with all new bearings and seals.
• Rebuilt the rear axle with new bearings and seals.
• All new brake rotors, pads, master, and booster.
• Put thicker oil in the transfer case.
• Changed transfer case input, and both output bearings and seals.
• Replaced the transfer case with a used one in good shape. It was cheaper than a shop press and bearings to swap idler bearings.
• All 4 new driveshaft u-joints.
• I did a bit of exhaust work. This was mentioned in my search for a potential cause but it is not rpm dependent.
• Changed transmission solenoids.
• Changed trans fluid several times.
• Wheels and tires have been changed.
• Pulled front and rear carriers and inspected. Look good.
• Cranked down the pinion nuts a touch to see if the noise changed.
• Rear spartan locker.

Thoughts –

• Removing the shafts and axles/flanges should have eliminated the pinion or carrier bearings from the equation. This should leave something on the wheels, breaks, transfer case, or transmission.
• Engine eliminate due to rpm not being tied to it.
• Transfer case eliminated due to the swap unless the replacement has the same issue.
• I think everything on the wheel/break/bearing side is eliminated.
• Transmission elements tied to driveshaft speed (after gear selection internals) still suspect.
• Oddly it sometimes it stops when it’s raining and the roads are wet.

Video of the noise -


Pic of the rig -

 

[voodu3]

Have you checked your windshield seal and or your sunroof? It sounds like wind noise to me from the video.

 

[voodu3]

It could be the roof rack bars too. I didn’t see them at first.

 

[ajax1]

On the wind noise my 95 had a whistle at around those speeds, found a Toyota service bulletin talking about this. Was the belt molding on the pass door, for some reason mine was missing a piece of foam, replaced it with an older one I had and it fixed the issue. Not sure this is your issue but you could pop the belt moldings and see if the foam is in place still.
If you do this be gentle they are held in place by white plastic clips which you can still get. Gently pop them straight up

 

[Rusty Marlin]

That sounds electrical, like feed back through the radio.