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1994 GMC C1500 Buzzing Noise

Tiny
JRL
  • MEMBER
  • 1994 GMC C1500
  • V8
  • 4WD
  • AUTOMATIC
  • 170,000 MILES
Hi guys -

I have a buzzing/ticking noise. It almost sounds like the kind of buzzing you get when the car stereo picks up interference from the ignition system, but it's not coming from the speakers. It seems to be coming from the floor near the 4wd shifter. It speeds up/slows down corresponding to engine RPMs. It's not real loud and when you're on the road you can barely hear it. I just bought the truck and didn't notice it during the test drive. Truck performance does not seem to be affected and I can get in and out of 4wd --- however there's a bit of a grind going from low range 4wd to high range.
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Monday, February 16th, 2009 AT 5:22 PM

8 Replies

Tiny
2CARPRO JACK
  • MECHANIC
  • 11,533 POSTS
Does it speed up and slow down with rpm or with truck speed or both? Could be the front pump in the trans whining. If you get under the truck can you pinpoint where it is coming from?
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Tuesday, February 17th, 2009 AT 7:39 AM
Tiny
JRL
  • MEMBER
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Jack -

It speeds up/slows down with engine RPM, but NOT truck speed.

I got under the truck yesterday but the noise gets drowned out by the engine noise so easily it's hard to pinpoint where it's coming from. I'll try again this evening.

Another way to describe the noise is like the ticking sound a cabin heater fan might make while running.

It's not the fan though.
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Tuesday, February 17th, 2009 AT 6:24 PM
Tiny
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I was just under the truck. You can't hear the noise outside the cab. It gets totally drowned out by the engine.
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Tuesday, February 17th, 2009 AT 8:16 PM
Tiny
2CARPRO JACK
  • MECHANIC
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So it is more of a "card in the spokes of a bike" kind of noise? Could be a pinhole exhaust leak making an almost ticking sound. Check the trans and motor mounts for anything touching metal (frame) you may be hearing a vibration caused by a bad mount transfering up the t-case shifter
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Wednesday, February 18th, 2009 AT 7:44 AM
Tiny
JRL
  • MEMBER
  • 5 POSTS
Yeah, you could say a "card in spoke noise". However, it doesn't sound like an exhaust leak. The mount vibration I'll keep in mind.

Funny thing is, when I step on the gas after sitting at a stop light you hear a slight change in tone.

It's almost like something wants to engage or some linkage barely touching a gear or other moving part. I'm just throwing that out, but that's what it reminds me of.
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Wednesday, February 18th, 2009 AT 8:04 AM
Tiny
2CARPRO JACK
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Try getting under it and putting along screwdriver up againt the t-case then the other end(handle) press behind your ear. You will be able to hear noise that way. Like a stethoscope. See if you can pinpoint the source. May be the t-case chain slapping or the shift fork bushings worn causing it to not move full into and out of gears
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Wednesday, February 18th, 2009 AT 8:07 AM
Tiny
JRL
  • MEMBER
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I used the stethoscope and found the noise loudest.I mean really distinct. On the 4wd shifter. Not quite so loud or distinct on the transfer case itself, but since the shifter assy. Is just a couple lights and a linkage it's gotta be the transfer case.

I took it out on the grass/mud and tried shifting in and out of 4wd. It goes fine from 2 hi to 4 hi and back --- it grinds going going in and out of transfer case neutral. On both 4 lo and 2 hi.
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Sunday, February 22nd, 2009 AT 8:24 PM
Tiny
2CARPRO JACK
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First be sure it isnt something like a shifter bushing causing the noise. This may be a worn shift fork bushing, or possibly a chain noise, it would have to be taken apart to see exactly what the problem is. Price varies depending on what is wrong, try calling a few local shops and get estimates, that will give you and idea of what you are looking at. Times like these, you may get more of ad eal than you would have 6 months to a year ago
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Tuesday, February 24th, 2009 AT 7:40 AM

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