Hoping someone has had this happen to them, and can aim me in the right direction.

my 1981 F-150, 4x4, with a 351M/C6 auto, has developed a mysterious rattle that has a bit of a ringing tone to it(like a bell).

The truck uses no oil, gets regular oil changes/grease jobs. It doesn't overheat, charge is fine...etc. All systems look to be go, except for this rather annoying noise...which I might add isn't consistent, or continuous!

There are times it starts the second I start to turn it over, and others where it won't appear until I start to accelerate. I've noticed that it definitely has a lot to do with engine rpm, as it will change pitch, and usually queit down a lot if I even as much as release the gas, or even quiet down more with brake application.

If the rain will ever stop here, I'll start with disconnecting the belts for a brief moment, and crank it over, and then connect them up again, one by one, and hopefully eliminate the p/s pump, water pump and alternator.

I do have a cracked exhaust manifold, which isn't making noise from under the hood any better, but I've never had one create such a rattle/clatter/ring tone before. At highway speed, it's deafening. I've travelled to far on it for it to be a bad bearing...the crank or a rod would have surely given way by now, and that generally creates an engine shake/physical vibtration you can feel.

I'm off to Princess Auto on days off to grab a stethescope to hopefully help narrow it down, as well.

 

Odd indeed!
All I can think of is that the drive shaft is hollow and would tend to "Ring like a bell" if being struck. Also RPM related. I'd at least give it a look/see. Good luck.

 

Well....got some kind of answer on the noise issue today. I left my house, tried to cross one lousy intersection, and suddenly, I had no gears...forward or reverse. I'm hoping it's the t-case that let go, and not the transmission... Anyways, she's down the street in the shop. This isn't a job I want to tackle in the back yard with the amount of rain we've been getting lately.

 

Hope you find out it's something easy/cheap to fix. I was going to suggest that your flex plate is cracked and your engine harmonics allow it to drift over and catch either the starter gear or the inspection plate. Please let us know when you find something out.

Ernie

 

The flywheel cracked, and broke....that was the final diagnosis. 6.5 hrs to remove both driveshafts, t-case and trans, r&r the flywheel, and possibly the converter, re-install. I'm letting the shop do it, as it's not a fun job out in the back yard, or even on the floor of a garage. Since it's all going to be out, and easy to access, I'm having the broken neutral safety switch replaced, and the transmission mounts. No point in being back at the shop a few months down the road to have something that expensive looked at again.

 

I have a similar noise ringing/ screeching. I think I've narrowed it down to the dust cover for the pinion seal on the rear end. It's loose and I can see where it's been wearing on the drive shaft and rear end. Does anyone know of an easy fix for this? I don't want to spend a lot of money until I get the engine to run right, ie. new rings.. thing smokes too much, and #3 piston is low on compression.

 

Glad it happened close to home!

I've had a radiator leak hit the fan blades and make a pinging sound. Another time it was a broken rod! Ting ting ting! Pull the plugs and turn it over. Hmm, why isn't that #3 piston moving?

-Ed

 

It's moving, the compression on it is is about 30 psi lower than on the rest of them. I think the rings are shot, I think the valves are burnt and mis adjusted too. Like I said I think the noise is coming from the rear end, coasting with engine off it's still there. It's speed dependent. Not RPM or engine noise.

 

I was actually replying to RR4E, the #3 reference was just a coincidence, as that's the one I broke a rod on. Still seemed to fit your situation though, Benztechnc, lol! Sorry for any confusion. I wasn't saying what anyone's problems might be, just what happened to me.

With your problem, maybe find a quiet stretch of pavement and coast in neutral. If you or a buddy can hang out the door or walk alongside, you may be able to pick out the source of the noise. Or put it on blocks and spin the wheel by hand, that would be safer than falling out of a moving truck!

-Smoky

 

LOL. I think I'm gonna play it a little different thanks for the input though. I'm just going to put it up on my lift at work and stick her in gear, and let her run with the tires off the ground and go over her with a stethescope.. when I get the time. I just wish I had more experience with these kind of trucks.. I'm not even sure where I want to take her, or do with her.. half the time I think of just rebuilding what I got.. then the other half of me says.. 460!!! The dilemmas we go through...