Hum from transmission tunnel area?

[Daniel81DMC]

Heya guys - long-time reader, seldom poster - mostly because my DMC is usually running quite well apart from easy-to-fix age-related repairs. As an aside, I've owned the car for nearly ten years, now (I'm 30, it was great taking the DMC to university!).

I noticed just the other day a low, constant humming coming from my transmission tunnel area (I have the 5-speed in my '81). I *barely* heard anything in the cockpit of the car, but as I am sure you guys know, we all get very used to how our D's sound. Putting my head down near the gear-shifter, I could hear the noise more clearly - no grinding, nothing really nasty, just a constant humming, and I don't remember it ever being there.

The car is low mileage; there's only 53,000 miles on the Odometer, it's been babied its whole life (I'm the second owner, but have every nut and bolt receipt right back to '81 from the original owner), and the only transmission work it ever had was a new clutch about five years back which can't have more than five thousand miles on it.

Any thoughts as to what this could be? Could it be something other than the tranny, just something in the area?

I should mention that my general understanding of cars is quite good, but I'm no expert, I'm a hobbyist, and the DeLorean isn't exactly the same as the Corvettes and Trans AM's I am used to.

I apologize for the rather vague description - I'd get sound-byte if I could, but I don't think the recorder on my IPhone is sensitive enough.

[Spittybug]

Maybe a fuel pump humm?

[Bitsyncmaster]

What's your VIN?

There is a problem with a nut backing off that mostly occurs on early VINs.

[Daniel81DMC]

Interesting; I replaced the fuel pump about four years ago - the sound *is* similar to a fuel pump noise, but it doesn't seem to be coming from the tank area, it's coming more from the tranny-tunnel area.

By they way, my VIN is 2991 - built in August of 1981.

[tgraham]

You didn't share a few important pieces of information to help narrow things down: is the ignition ON, accessory electrics ON, car moving/rolling, and/or engine running when this noise is being made?

I'm guessing it's probably not moving since you mention putting your ear near the shifter to hear it... but...

Travis

[Daniel81DMC]

Car on, ignition on, everything running; the hum is *barely* audible when driving.

[Soundkillr]

Could be fuel pump accumulator. My bracket was slightly loose and allowed it to barely rub inside of frame. Made a high pitch whine. Moved the bracket some, tightened it back down, now no more noise. Btw it is located in the transmission tunnel.

[Daniel81DMC]

Interesting - would that be the accumulator "going", or just it randomly coming loose?

How would one check either way? Easy to get at?

[Bitsyncmaster]

Could be fuel pump accumulator. My bracket was slightly loose and allowed it to barely rub inside of frame. Made a high pitch whine. Moved the bracket some, tightened it back down, now no more noise. Btw it is located in the transmission tunnel.

That is a good guess. One of the funtions of the accumulator is to absorb the pulses from the fuel pump. So it the accumulator was "shot" you may get the pump noise at it. Of course it could also be the bracket or foam rubber on the accumulator.

[David T]

Check the motor and transmission mounts. One can be cracked. Check all of the rubber bushings in the pivot points for the shift linkage. Make sure the rubber cover is in place over the shift mechanism in the console. As long as you are looking check the fuel pump and the boots to make sure everything is where it should be.
David Teitelbaum