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Discussion Starter #1
New to this forum, got a lot of info when I was buying my truck 2weeks ago. I have a 2004 6 speed with 3.73's with about 73000miles.

Ive had it for 2 weeks and and there is this absolutely annoying whomping sound coming from it in 6th gear at around 45-55mph from underneath. Its like a very low pitch hummmmmmm-hmmmmmmmm every second or so. I didn't notice it at the dealership when I test drove it. Got on the interstate to take it home and didn't notice it. When I took it down a back country road at cruising speed on the flat I noticed it real bad. To get it to go away I can put it in 5th gear but then I but then im running 2200rpm. If I step on the gas or let off the gas it goes away, but just cruising its noticeable. As I said only in 6th gear. Not sure what to do, took a risk buying her with no warranty, hoping this is not TOO major
 

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what kind of clutch is in it? my dual disk makes sounds occasionally if I am in the wrong spot in the power band. it is usually below 40 in 6th though.
 

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Discussion Starter #3
My first thought is maybe thats just the way it is with the power-band. The truck is stock and was VERY well taken care of by an older guy, absolutely perfect kept service records so Id image it is the original clutch
 

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Well the miles sounds perfect for the u-joints to be shot. I bought mine and 3 days after taking it home had simliar problem. I changed all 3. Hopefully it could be that simple.
 

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Discussion Starter #5
Have to try that.. Its just weird that It only does it in 6th gear at that speed at that engine load, no other time. Perhapse thats just the perfect resonace.

Hoping its nothing major
 

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I had a funky vibration in my truck at 45-55 MPH in either 5th or 6th gear earlier in the winter, under cruising conditions. Feed it a little gas or lift off the throttle, and it went away. I thought that it was an engine miss at first, but then it turned into a knobby tire feeling when slowing down from around 25 MPH even with the clutch pressed in over the next month. Long story short, I finally had time to drop the rear driveshaft today, and one axis of the rear U-joint nearest the differential was seized solid.

What happens if you feed some slalom-type steering inputs into the wheels at the vibration speed? If it gets worse or goes away, it could be a wheel bearing going south.....
 
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