S2, humming noise from back end.

[Mark_944S2]

The other day I'd been cruising down the interstate at 80mph, and pulled off at an exit. I was then merging into the traffic, and doing about 30 in second gear, when I heard a loud humming noise from the back end. It went away after 10s or so and I couldn't reproduce it. No other symptoms really, everything seems fine.

Any ideas folks? A wheel bearing springs to mind, or transmission (please god no!) problem!

Thanks,

Mark

[fast924S]

Hey Mark, I would check to make sure you have the right amount of tranny fluid, if there isnt enought those trannies will humm, Also it could be a wheel bearing, but I would worry about it too much if it onyly happened for 10sec if it comes back and last then check it out other then that just keep an eye on things back there

[SoCal Driver]

The fuel pumps sometimes cavatate (catch a little air) and make a humming noise.

[Mark_944S2]

Thanks you guys,

Will check the transmission fluid anyway this weekend, although what SoCalDriver said makes sense as I was really low on fuel at the time and had just taken a long, sweeping bend really quick, so maybe the fuel pump ran on air for a few seconds.

Mark

[SoCal Driver]

Don't run the fuel pump dry very often. The fuel actually "lubes" the pump -- the armature is immersed in it.

Think of the 747 center fuel tank effect.

[Mark_944S2]

Yeah, now its happened once I'll try not to run it so low.

Glad its not the gearbox anyway (hopefully) !

Mark

[postmark]

I have a question about cavitation. I have that same humming noise from the fuel pump, how could it be sucking in air with a full tank? I thought at first it was the pump itself, but that was an expensive dead end