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I have a mystery. Trucks runs fine and no mechanical issues, but when I am on the gas about about 3/4 throttle, there is a very loud chirp or squeak that comes from the enginee compartment. If I let off the gas below 3/4, it quits. It does not appear to affect anything mechanically and I cannot reproduce it when I am not moving. It sounds like it is in the fuel linkage somewhere, or maybe in the carb but I can't track it as I can't be under the hood while moving. Does anyone have any idea what could be causing this and how to fix it?

Thanks

Jeff

fan belt?

My old 1947 Harley usedto make a sound like that when the head gasket was leaking.

Check the fan belt tenssion it may be slipping under load.

hb

I had a similar chirp a couple of years ago-turned out one of my floorboard bolts was hitting the transfer shift linkage-going to a shorter bolt eliminated it.
Gary

Mine had a chirp or screetch going down the road under throttle also. Drove me absolutely crazy. Ended up the two main mount bolts at the bell housing were just loose enough to allow the winch lever to come in contact with the transmission cover. I tightened them and chirp gone! . The throttle linkage comes quite close to the exhaust manifold at the rear, but I don't think it could chirp that loud. John

Classic is fan belt slipping under load. Out of adjutmdnt (too loose), old belt (glazed), grease or oil on belt or pulley.....at idle under no load they have enough friction left but when rhe rpm goes up and the belt gets loaded they slip and give that classic chirp chirp chirp sound. New proper size belt adjusted to proper tension with a clean pulley may fix. At the very worst you'll have a new pulley installed and checked. But as you can see byt the posts it could be something else.

Could be a very small leak around an exhaust manifold port gasket, or at the hot spot gasket where the intake and exhaust manifolds meet in the middle. Could be a slight crack in the exhaust manifold. If this were to be the issue, most likely you would hear it when accelerating such as winding up through the gears or anytime the engine is under any significant load, regardless of RPM. Could also be the result of a very slight external head gasket leak that isn't large enough to cause a skip yet.

On a less serious side, it could be generator or water pump bearings, or something as minor as a drive belt. You'll have to do some serious looking.

MSeriesRebuild wrote:Could be a very small leak around an exhaust manifold port gasket, or at the hot spot gasket where the intake and exhaust manifolds meet in the middle. Could be a slight crack in the exhaust manifold. If this were to be the issue, most likely you would hear it when accelerating such as winding up through the gears or anytime the engine is under any significant load, regardless of RPM. Could also be the result of a very slight external head gasket leak that isn't large enough to cause a skip yet.

On a less serious side, it could be generator or water pump bearings, or something as minor as a drive belt. You'll have to do some serious looking.

Charles is right, check your manifold nuts to make sure they are tight

If your truck is like mine then check the cowel vent ( right in front of the windsheild ) I have mine closed and there is still a slight opening and it acts like a wistle but dosent sound like one.

I have a low pitched whistle sound which comes on at about 1/3 to 1/2 throttle when moving. It will not do it parked. As the driver of the vehicle, I swear it comes from the left side of the engine, but my wife in the passenger side says it comes from her side. I may have to open the hood and go down the road with someone in the engine bay