Sustained squeal (think crickets chirping) starts above 15 mph when hot

[flynylon]

Hey y'all

My bronco is making a sound once it gets all warmed up and goes faster than about 15 mph. The sound is like a field of crickets chirping loudly, and it's almost constant when rolling down the road. It sounds like it's coming from underneath, but the pitch is so high and limited ability to move around has made it hard to pinpoint the source.

The one thing that came to mind was the speedometer cable or something along those lines, since it only happens above a certain speed. When you slow down below 15-20 mph, it goes away. It's not there when it's cold either.

Anybody got any idea where this maddening sound is coming from?

Thanks!
mike

 

[Viperwolf1]

Rear wheel bearings maybe.

 

[gearida]

Vet your buddy to lay on a creaper whe you drive it. No really. If you think it is the speedo then diconne t it and drive. Can you change the sound by turning or leaning the truck? How about if you apply the brakes... More hints are needed.

 

[Quick & Dirty]

Many years ago I had a driveshaft CV go bad, and if I remember right, it made a chirpy sound before it went. It was running dry, as some old grease/gunk kept the fresh grease from getting in the little pinhole style fitting.

 

[broncnaz]

Losts of possibilties. wheel bearings loose or going bad, brakes dragging or brake parts broken and rubbing, Ujoints worn. could also be any sheet metal parts like guards or shields that warm up and vibratate at speed. Theres probably a bunch of other things it could be as well. I'd also check the fluid levels in your transmission, t case and axles.
Does it only do it while driving?

 

[flynylon]

Thanks y'all. The sound starts happening whenever I am rolling down the road after it gets to operating temperature, and from there, it just gets louder. It doesn't change when I hit the brakes.

Originally, I thought the sound was coming from the dash, but tonight, I stuck my head out the window, and I could hear it outside too. I had the kid come out and listen when I came down the street, and he said he could hear it 100ft away on the porch.

It's been happening for a while. I changed the T-case oil, but that didn't do anything. I checked the 3-speed tranny fluid, and it was over full when I pulled the fill plug, but I haven't had the chance to change it yet. I topped off the rear dif, but I haven't opened the front. I just got her back after a month at BC Broncos. They put a new 3.5 suspension lift with all new driveshafts and ujoints, so that stuff isn't the issue.

Now, the one time I checked the 4wd operation and the hubs, when I turned the wheels tight to the right driving on concrete, I could hear some clicking in the front hub (just like a bad CV). Of course, it doesn't do it when the hubs aren't locked. Maybe that joint or bearings are bad?

I did get new hub centers from BCB today, and I will be replacing them shortly, so I'll at least get to look inside the hubs soon.

It just seems odd that it only starts happening when it's hot, and it only happens when I go over 15 or 20.

 

[broncnaz]

Probably something in the driveshaft either the ujoints or the CV as was stated. Lifts tend to put extra strain on ujoints and if they were old to beigne with they are probably about ready to wear out. Sometimes the pinion angle is bad and will wear out ujoints very quick.

 

[flynylon]

The drive shafts are brand-new HD from BCB with brand new u-joints, and it hasn't stopped.

 

[1970mule]

i am leaning towards speed-o cable cause this happens to mine after about 25-30 mins of crusing over 45mph. i have not had a chance to disconnect the cable but i bet its that.

oh and if you can hear it out side also it could be the cable end near the trans case. or the whole cable.

 

[lars]

Rear wheel bearings maybe.

This would be the next place I looked. I had one make that kind of noise and chose to ignore it because I couldn't figure it out. Until the wheel attempted to depart the axle on a busy freeway and it became somewhat obvious.

 

[John Marinan]

Could it be the fan belt out of alignment? Look for rubber dust. My chevy did that, took a little while to find it.

 

[Justafordguy]

Did the noise just start after the lift & new shafts? Also if you can hear it from 100 ft away I don't think it could be the speedo cable.

 

[flynylon]

Lars, rear wheel bearings are on the list of things to get to, but sound seems to be coming from something in front of me as I sit in the driver's seat.

John, the fan belt is somewhat set back by the time it hits the alternator (bad spacing issue by the PO) but when I hit the clutch and let the rpms drop, it doesn't seem to do anything different. It's all about being above a certain speed.

And Justafordguy, no, this started well before the lift.

 

[rcmbronc]

Try greasing the front axle u-joints.

 

[dbevans2249]

I would put it up on jack stands and run it up to speed and try to locate it.

 

[Justafordguy]

X2, Get it warmed up and making the noise and then put it on stands.

 

[lars]

Lars, rear wheel bearings are on the list of things to get to, but sound seems to be coming from something in front of me as I sit in the driver's seat.

John, the fan belt is somewhat set back by the time it hits the alternator (bad spacing issue by the PO) but when I hit the clutch and let the rpms drop, it doesn't seem to do anything different. It's all about being above a certain speed.

And Justafordguy, no, this started well before the lift.

Well then maybe front wheel bearings, but...

Get it up to temperature. Speed up to well past the point where the noise is audible.

If you have a manual transmission, push in the clutch and coast. Noise still there? If an automatic, put it in neutral while coasting. Same test.

Depending on whether you have power steering/power brakes, you might even try turning off the engine and coasting. Even if you do have ps/pb, do it anyway- just find a safe place to try the test.

If the noise is still there while doing any of the above tests, then you've eliminated anything related to the engine as being the culprit.

Try sawing the wheels left to right. Does that change the noise? If so, then it's probably wheel bearings.

U-joints in the front axle shouldn't make any difference unless the hubs are locked and/or the transfer case is in 4wd (I'm guessing not).

If you want to check the speedometer cable theory, undo it at the transfer case. Takes a minute with a pair of large pliers. Then go for a drive.

 

[flynylon]

Found it

Update. I did lift up the back end and ran it hot. The sound was coming out of the D20 at the output shaft. I think it's just the dust cover rubbing when hot, but I am not really messing with it at the moment. I picked up two D20s. One was just rebuilt by an off-road shop down here in San Antonio within the last two years, and it is already twin-sticked. It will be going in soon, and I can get the other one out and rebuild it as a backup. Not sure what to do with the third one.

Thanks for all your replies!
mike

 

[lars]

Update. I did lift up the back end and ran it hot. The sound was coming out of the D20 at the output shaft. I think it's just the dust cover rubbing when hot, but I am not really messing with it at the moment. I picked up two D20s. One was just rebuilt by an off-road shop down here in San Antonio within the last two years, and it is already twin-sticked. It will be going in soon, and I can get the other one out and rebuild it as a backup. Not sure what to do with the third one.

Thanks for all your replies!
mike

I know what to do with all of them- sell them and use the money for a down payment on an Atlas ;D

Sorry, just kidding. I do like mine, though. And seriously, I just looked at your gallery. Nice, clean-looking Bronco you've got.