Hi guys,

Took a 830 mile road trip from Chicago to Norwalk, CT.

Had to drive through two snow storms, going over snow packed roads, freezing rain, snow, etc.

After the irst snow storm I was able to drive about 80mph for a while then hit freezing rain. Anyways after the 2nd snow storm, the roads dried an I noticed that when above 70mph there is a cyclic low pitched sound (crescendo decrescendo pattern) that I haven't figured out where it is coming from. The sound lasts about 1 second and cycles about every other second at 70mph. The sound gets louder the faster I go above 70mph, loudest at 75mph. Sounds like a rubbing sound, not grinding or tinny.

I can only hear it with the radio off and the windows up otherwise the exhaust is too loud.

There is no vibration I can feel associated with the sound and no decrease in speed or tugging felt from the rear of the car.

Mods are in sig but could it be coming from one of these two mods?
Spydershaft
4.10s

About a month ago I had the Ford dealer replace the bearings and gear pin in the rearend. Apparently the place that installed my 4.10s almost a year ago did a bad job and the gear pin was stripped and the bearings where not set right. That is combo with a possibly poor DS install regarding the preload on the crush sleeve and the pinion nut coming loose caused the bearing failure. No fault of the DS obvioulsy, just bad luck I guess. Anyways, the Ford dealer warrantied the rearend for another year so if it is a rearend noise its should be covered.

I was hoping for some help as I did not purchase the car in CT and I am here for another 8 wks so I wanted this fixed before my long trek home. I would like to point the service department in the proper direction so they can find the source.

Could this be a wheel/tire out of balance? Wouldn't it shimmy with the noise more constant and not cyclic?
Could this be a problem with the gears or new bearings?
Could this be a problem with the driveshaft? I never had any vibrations after the DS install a long while back and had the car well above 70 with no noises.

Thanks so much guys, I want some specifics to tell the service peoples otherwise they could have the car for awhile and never find the source.

UrS4

 

I would get up under the car and look to see if anything got stuck somewhere when you were gong thru the bad weather. Other than looking closely underneath to see if something came loosethat is the only advise I can give. Sorry!

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Sounds like rearend noise, if it was a driveshaft their would be vibration.

I dont, tink it would be tire noise but you could rotate them to eliminate that part .
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What in the rear end would cause this cyclic rubbing sound? Wouldn't at 70mph+ the gears and bearing be spinning so fast that the sound would be constant like a whine sound or grinding sound?

 

Also may want to check the brakes. Mine make weird noises at around 45mph. I've probably warped the rotors or something and now it is just moving the calipers around on the sliders without any lube.

 

Okay, I went out and tried to see if I could pinpoint the location of the sound.

At 75mph and higher, I also now get the left side of my dash to have a little buzz in cycle with the sound.

So does this mean it has to be a vibration transmitting up through the dash? Does this mean that the vibration could be coming from the front half of the car?

Or does it mean that the frequency of the sound is causing the dahs buzz via resonance?

 

check under the car where the hanger's mount at the trans crossmember aren't hitting metal had that problem on my last mustang with pypes set-up.

 

Is the sound like a wom,wom,wom?

 

Yes I guess so. Each wom last a little under 1 second at 75mph.

 

Sounds like you need to adjust your pinion angle. I believe several people have had this after installing aluminum driveshafts and or torque limiters. People usually don't notice it until an extended trip with the MPH being the same for an extended period. I also noticed that ford replaced some parts in the rear end, they could've turned your driveshaft 180 degrees from what it was or torqued things down differently.