Un-ballanced propeller shaft - or Drive shaft

[NDearyan]

I bought a 1993, 1 ton, 4wd, "The black beast"

At about 40 mph to 50 mph, and no load, there is a noise like an un-ballanced driveshaft, or propeller shaft.

I suspect that due to some rust underneath, that the added weights on the front or rear drivelines has come off. So, I hear the noise, and feel some vibration.



When all the lockouts are out, and the rig is running in 2wd, typically the front shaft, and axles do spin, just due to a little friction in the front hubs. Even though they are not locked in.



It feels like it is the front propeller shaft.



I usually hear it at no load, or small loads.



Would it be a good idea to tie the front shaft up with light string, to keep it from free-wheeling, to see if the vibration is comming from it?



And, after I do find the source, of the vibration, (I'm pretty sure it is a front or rear driveshaft, and I'm assuming that is it) then who do I take it to, to get them ballanced?



Thanks,



Nate

 

[CChase]

Jack it up off the ground (SET ON JACKSTANDS), engage the transfer case in 4hi and have somebody run the accelerator to the RPM which you are seeing the vibration at.



When the vibration occurs, go to both driveshafts and at each end and the middle, hold a piece of chalk or a greasepen up to the shaft just till it barely touches. Then shut rig down and examine the shafts. If you see a consistent thickness in the line you drew around the driveshafts then they are balanced. If you see it get heavier and lighter in thickness, then you have an out of balance shaft. Where a balance problem is indicated, put two hose clamps on the shaft and put the adjusting parts at the thinnest point of the line. Retest and adjust the positioning of the hose clamp adjusters as necessary, just be sure as you rotate the hose clamps, that you move both of them an equal distance in the opposite direction.



If you don't want to do this test, take you shafts out and take them to a driveshaft shop. If you don't know of one, call the fleet manager at a local trucking outfit and ask them who they use. A driveshaft shop can balance them, and the cost would be (I'm guessing here) $50-100 for the pair of them.

 

[drrhoades]

Check for worn u-joints.

 

[SRadke]

First check for loose u-joints. Generally you won't hear an out of balance shaft.



Second, it sounds like your hubs are not totally disengaging. They should not have enough friction to spin the axles, gears and driveline at highway speed.



-Scott

 

[CChase]

Don't you guys know you have to drop the engine out from underneath to change the valve cover gasket..... I think this is why I have a flat forehead, from smacking myself for doing the hardest things first..... Doh!



OK, first check the simple things... . then go to more complex (read as more work). Maybe I should paint KISS in my engine bay and somewhere on the underside of the truck.

 

[drrhoades]

You dont have to take the shafts out to check the u-joints and even if you do its not hard. Plus Holding a piece of chalk up to a shaft under a truck on jackstands doing 40 or 50 mph isnt exactly the safest thing to do. You should be able to see where the weights were if they did come off. If that is the case then go get it rebalanced at a good shop. If that is not the case then check u-joints. If the joints are greaseable try greasing them and purge them correctly with fresh grease coming out of each bearing cap ( this is very important). If rust colored grease comes out right away then I would replace the u-joints because that means that water has gotten in there and eaten at the trunions and the needles and things are only going to get worse.



I had a odd noise/vibration on my 94 F-150 that turned out to be bad u-joints so I replaced them all. It was right between 40 and 50 mph and kinda hummed at you.