Maybe a bearing issue ?
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Maybe a bearing issue ?
I am about to work on rebuilding / replacing a 351C engine, vintage 1974, that has a noise that reminds me / sounds like a squealing bearing. The engine runs, compression is reasonable good on all cylinders but with this noise I am afraid it won't run much longer. Fair to say the engine does not run very smooth . My mechanic's stethoscope tells me the squeal is at the back of the engine. When just turning the engine over (coil unplugged) there is no squeal. Shifting the C6 transmission into any gear does not stop the squeal either. looking for anyone's thoughts on if it could be a transmission issue and not something like a crank bearing.. Thanks to everyone.
Tuned
Joined: Jun 2014
Posts: 475
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From: Vermont
Even tho' it sounds like the rear of the engine have you eliminated all external,turning parts? Usually my 1st try at hard to find engine noise is to remove the fan/pulley belt(s) which of course tells you whether it is an up front rotating thingy that is transmitting the squeal. If you have eliminated power steering,alternator etc,etc, by doing this then I don't dare to guess any deeper. Good luck,gary
Lead Driver
Joined: Jul 2017
Posts: 9,600
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From: San Jose, CA
Agree totally with that. Remove the belts first.
Doing so may also change an internal dynamic by changing the tension on the end of the crankshaft, but not sure how that will effect what you have.
Also, the transmission's pump can make that noise. One of the worst sounds ever to come out of my '79 was a (thankfully!) momentary squeal after it had been sitting for awhile. Luckily in my case it did change when I put it in DRIVE, so I messed around a bit and shifted through the gears.
It went away and lucky for me never came back. But it's been sitting so long this time I'm very concerned it might crop back up. We will see.
Most engine bearings don't squeal (at least not in my experience) but instead make knocking noises that you use to determine if it's a main bearing or rod bearing, based on the type and frequency of the sound.
A roller bearing will squeal, but those are mostly in the transmission and the accessories.
Good luck.
And if you get the chance, post up a video clip of it.
Paul
Doing so may also change an internal dynamic by changing the tension on the end of the crankshaft, but not sure how that will effect what you have.
Also, the transmission's pump can make that noise. One of the worst sounds ever to come out of my '79 was a (thankfully!) momentary squeal after it had been sitting for awhile. Luckily in my case it did change when I put it in DRIVE, so I messed around a bit and shifted through the gears.
It went away and lucky for me never came back. But it's been sitting so long this time I'm very concerned it might crop back up. We will see.
Most engine bearings don't squeal (at least not in my experience) but instead make knocking noises that you use to determine if it's a main bearing or rod bearing, based on the type and frequency of the sound.
A roller bearing will squeal, but those are mostly in the transmission and the accessories.
Good luck.
And if you get the chance, post up a video clip of it.
Paul
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Thanks Gary and Paul, I know it's gonna be interesting when I get that far in the tear down. BTW, I have checked all the external items attached to the belts, took off the valve covers, watched all the lifters go up and down during cranking, I am able to spin all the push rods ( hopefully not bent ) and each cylinder has equal (ish) compression. So I guess I will have to dive into the motor for a better look-see....... Plan is now to pull the motor and tranny as a part of the complete make over. As a new user/member I will post pictures once I figure out how LOL.
Lead Driver
Joined: Jul 2017
Posts: 9,600
Likes: 1,174
From: San Jose, CA
I wonder if a torque-converter bolt is working it's way out and rubbing against something?
Lots of things can make noise on these old trucks. Yours is an interesting case for sure. Be very interested to hear what you find.
Good luck. Hopefully even if you have to tear down the engine to find it, it still ends up being an inexpensive fix!
Paul
Lots of things can make noise on these old trucks. Yours is an interesting case for sure. Be very interested to hear what you find.
Good luck. Hopefully even if you have to tear down the engine to find it, it still ends up being an inexpensive fix!
Paul
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