What is inside the exhaust pipe?
 

I have been chasing down a squeak/squeal coming from underneath the car. It happens when I let off the clutch and for a second or two after full clutch release as I am applying power. I have replaced the throw out bearing & slave cylinder, checked all the bolts. I'm down to either the clutch itself slipping or something in the pipe.

Question: is there anything inside the pipe that may be squealing? A baffle or something where the weld is coming loose and the pressure change from off-throttle to on-throttle causes it to wiggle and squeal? I'm about to pull my hair out over this noise.

Anything is possible but normally a loose baffle or muffler inside the exhaust pipe would make more of a rattle than a squeak. Can you get the car up on a rack where someone can operate the clutch while yoiu are under it watching and using a stethoscope to chase down the squeak. They can be hard to locate and it may not even be close to where it sounds as if it is from above.

Ron

It doesn't make the sound when the car is off or when operating the clutch at idle. Only under power during acceleration. I've been under it while on the lift while the clutch was pushed and everything looks fine and no sound. I could get it up on jack stands and run it but don't think it would recreate the problem without load.

I don't have a dyno in my garage to simulate a load...

Have you checked the U-joints? If even one of the bearings is dried up, it could be causing the squeal under a load. Just a thought.....

I thought about that. If I add grease to the fitting on the u joint, will that grease all four lobes? Can I grease it installed or should I remove the while driveshaft from the car?

Standard practice is to grease them in place, assuming that you have a zerk fitting of course. You should pump in grease until you see it coming out of each lobe around the bearing seal area.

Right. That's next on the list then. I also need to recheck the driveshaft angles again....
Thanks

Here, watch this video from Spicer on lubing your u-joints. You want to pump the grease until you clearly purge all four seals. Do not stop at the first. Go here: http://ujoint.kickme.to

Yup. Losing a u-joint and/or drive line in these things can be quite troublesome, and that's assuming you have a safety hoop over the driveline. If not, a little more than troublesome.:eek:

Great video! Thanks.

Lonestars have the built in driveline hoop above and to the sides the driveshaft to protect the passengers. I've thought about adding a 360 degree one.

Not necessarily during clutch application.

They generally make noise anytime the input shaft is slower than the crankshaft, especially if the input shaft is stationary, as clutch in, in gear.

Once the clutch is fully engaged, the noise stops.

Ok, I don't know what a spigot bearing is. I have a 1982 351w block stroked to 408. I have the bearings that came with the 408 kit that I got from blykins. Rear main is a two piece rubber seal offset by 1/4 inch. I don't remember installing any brass seals or bearings.

Ok, Mr Google also says this is a pilot bearing. I have a roller pilot bearing.

Correct, pilot is more self explanatory, spigot is another name. :)

Those can also cause a squealing sound when the lubricant is gone and the bearing begins to wear out.

Ted

Well, it wasn't the u-joints. Took off the driveshaft since I couldn't get my grease gun on the Zerg fitting - re-greased and re-installed. Still makes the noise.

I did notice that it doesn't seem to do it in first gear from a stop. Only when going from one gear to the next while moving. It definitely makes the squeal for 2-3 seconds after the clutch has been fully released. So, unless there is significant slipping of the clutch, I don't think it is the pilot bearing.

So I guess I'm back to the pipe. I guess it could be clutch or transmission, but it sounds like it is coming from the pipe.

:confused:

If you have access to a bore scope, send it into the pipes and look around. If it will take pics, even better. Maybe time to check all wheel bearings as well?

Don't know if it means anything but I found that my timing pointer was 4 degrees off today. Checked with a piston stop and found the 4 degree discrepancy. I have noticed a decrease in power lately and some misses at high to WOT.

Today I took off my vacuum advance to see if I was over-advancing at high throttle (not WOT) causing detonation/missing. This made the miss worse, even causing a backfire thru the exhaust.

When building the engine I had way too much slack in the timing chain so I had to get a shorter chain (don't remember how much shorter but Clovis made a double roller that was shorter). To get the cam with the shorter timing chain within specs while using the degree wheel, I had to install the cam 8 degrees advanced instead of straight up. I can't do the math in my head, but would the advanced cam combined with the retarded timing cause the miss and/or squeal? I was actually only running about 32 degrees total - all in at 2500 rpm.

I think that when I had the vacuum advance attached, it was advancing a little at heavy throttle "protecting" the engine from too little timing. Without the vacuum advance, it was too retarded and started backfiring. I set the timing mark to 41 degrees (41-4=37 actual degrees total). I didn't get to test it before having to come to work.

Any thoughts on if this could be the cause of any of my problems?

If you have a ceramic clutch....they can squeal a bit too.....

This is a way stupid question and not intended to insult you at all, but have you checked the belts and the alternator pulley? Sorry, just trying to think of things that squeal...