[edhhjr]

Hi all, newbie here. Have a 79 with a 350/350 both from the mid 1970's rebuilds, unknown miles) and a noise I can not figure out. It sounds very much like a loose drive belt, but with more of a metallic sound. And high pitched, like something spinning fast. Removed all the drive belts (ps, water/alt) with no luck. Only does it while moving under acceleration, forward or backwards. Will not do if the car is standing still (neutral or power braking). Will not do it under very light acceleration or cruise.

One other strange thing, only happened once. When I pulled the vacuum hose for the shift modulator, it made a loud knocking sound. But only did it that one time for 10 seconds. This might need to go in the trans section, but the sound is near the front of the motor. Any idea's? thanks

 

[Keyser Sose]

bearing going bad in water pump or alternator? timing chain slack scraping inside of timing cover?

:dontknow:

 

[edhhjr]

drove the car without belts for 10 seconds, still made the noise. It does have a new timing chain/gears.

 

[hotrodelco]

U-joint:texas:

 

[69 SS396]

U-joint:texas:

X2

 

[Tokageroh]

u-joint x3, id also suggest checking pinion bearing and wheel bearings just in case.

 

[Keyser Sose]

Hi all, newbie here. Have a 79 with a 350/350 both from the mid 1970's rebuilds, unknown miles) and a noise I can not figure out. It sounds very much like a loose drive belt, but with more of a metallic sound. And high pitched, like something spinning fast. Removed all the drive belts (ps, water/alt) with no luck. Only does it while moving under acceleration, forward or backwards. Will not do if the car is standing still (neutral or power braking). Will not do it under very light acceleration or cruise.

One other strange thing, only happened once. When I pulled the vacuum hose for the shift modulator, it made a loud knocking sound. But only did it that one time for 10 seconds. This might need to go in the trans section, but the sound is near the front of the motor. Any idea's? thanks

oke::dontknow:

 

[fauxrs]

do you have an oil pressure gauge? what does it read under those conditions

 

[LOCKJAW]

U joints will cry and vibrate when thet are comng apart..No time to waste or you will using shoeleather express.

 

[69 SS396]

U-joint noises travel. Could sound like its from the front while driving.

 

[BOOSTED-SS-ELKY]

Its usually too difficult to find noises while you're driving the car. Get a good friend and jack the rear of the car off the ground (Use jack stands) and run the car up to speed so you or your friend can walk around it and locate where the noise is coming from.

 

[HKDUP87]

Its usually too difficult to find noises while you're driving the car. Get a good friend and jack the rear of the car off the ground (Use jack stands) and run the car up to speed so you or your friend can walk around it and locate where the noise is coming from.

SMART!!!!!!:beer:

 

[edhhjr]

Update. Put it up on jack stands, got it to make the noise, but only in reverse. Still couldn't tell where it was coming from, since it only lasted about 2 seconds on the stands. Replaced the plastic u-joints since they were original with no change in the noise. Just took it for a run, can get it to do it all the way up to the speed limit while accelerating. Maybe I'll make a vid tomorrow. Thanks all for your ideas.

 

[aeilenstein]

Just FYI, I once had a trans cooler line (metal) slip out of place and just far enough over to rub the harmonic balancer. Made a metallic noise for sure, but this would not explain why you hear it only in drive.

Oh, SNAP! Check your flexplate. Many '70s small blocks had cracked flexplates. There is not necessarily a pattern to when the flexplate makes noise, but definitely only when moving, as the side to side forces of turning and acceleration can pull the cracks apart centrifugally.