Chassis "whine" - very mysterious.

[morgan]

I've posted before, but no solution found.

The noise sounds like a very fast "whirly-gig" party toy at super-RPM range.

The pitch increases and decreases directly with chassis rolling speed, and jumps an octive above 50 or 60 mph.

It starts off at about 20 mph.

It does not happen all the time. Sometimes dissappears for months, then comes back suddenly for a week or more.

Doesn't have to do with brake application, or steering, or under load, or coasting, or in a left or right turn. No increase in occurance in winter or summer. Wet or dry weather. New chassis grease or in need of PM. No difference at all. New tires or old.

Normally just starts when speed reaches 20mph, or can be initiated at a higher speed if I hit a bump in the road.

I've had this for so long, it's almost like an old ghost that I've learned to live in peace with, but it sure would be nice to end the mystery. Are there any mechanical clairvoyants or psychics out there that want to exorcize my truck?? :^D


Thanks for reading.

[Iain]

I have had a funny noise similar, there appeared to be no rhyme or reaso for it. Mine was more of a "tappity tap" sound (no not engine related!) that took me a long time to figure out. It ended up being a small piece of plastic vent material on the right side of the cowling area that was cracked and broken but was held on by 1 screw. The loose end moved ever so slightly with the correct air pressure/speed/wind/whatever to produce a small sound that annoyed the heck out of me unless I turned up the radio.

I pulled it out and glued it back together, remounted it and no more noise.

You might want to check your cowling area with the hood open and see if anything is loose.

Iain

[morgan]

I would love to find out that it is something like that and not a transmission or transfer case problem.

I may use a leaf blower to see if I can blow into the cowl to replicate that. However, I have noticed that windy conditions or stagnant make no change. Worth inspecting for though.

thanks!!

[gmctd]

Push yer odometer reset button in while it's razzin' ya - see if it gives up.

[morgan]

OK, I'll try anything now. Odo reset? I'll let you know!

I tried the leaf blower test. Nothing. I might get more intimate with the under-carriage though. Might be something not at the front/grill/bumper/intake area.

[Turbo Al]

I have had a couple of wierd noises coming from mine in the past one was the torsion bar rubbing against the trans cross member (bent member off roading) and it was very hard to see and track down. Another was a cracked trans mount (metal base of rubber mount) and it is also hard to see and track down -- actually got a buddy to put it in gear with ebrake on while I was under it for that one. Add a failing clutch pack and incorrectly set endplay on one rear axle and that just about does it for my 1993 as far as wierd noises went.

[Robyn]

If you put the tranny in neutral at speed will the noise stay or does it follow engine RPM??

[morgan]

Robyn, the noise follows chassis rolling speed only. I have tried the rolling neutral theory and it did not affect noise any differently than when in drive or other forward gear. thanks!

Iain, so far, this noise of mine only happens at speeds over 15mph or so. I have been tempted to get a buddy on a motorcycle to hover around me from different directions to locate noise, but can't think of anything better than that to instigate the noise and isolate the location. thanks!

[DennisG01]

You could try turning off the engine - it might help you to at least figure out what direction it's coming from. Then try opening and closing different windows to see if it gets more noticable or not.