Squeak when reversing under power

[Bryan G]

This is one of those problems that doesn't seem to hurt anything, aside from perhaps my pride! When backing up I hear a noise: squeak, squeak, squeak. I want to blame it on something to do with brakes but, oddly, I can push in the clutch and the car will continue rolling backwards without the noise. Foot off the clutch, the noise returns. Only in reverse. Ideas? Not a steady noise, more like something just hitting or rubbing intermittently. 

[plymouthcranbrook]

My first thought would be an issue with the U Joint. Perhaps dry?

[Los_Control]

I was thinking possibly the throw out bearing or pilot shaft bushing because it goes away with the clutch in.

U-joint is a very good possibility

18 minutes ago, Bryan G said:

This is one of those problems that doesn't seem to hurt anything, aside from perhaps my pride!

I feel it is a warning sign, while not bad now .....If you ignore it someday you may need the flat bed truck of shame to haul you home.

 

So asking about it is a good thing, is not normal to make the noise .... Better to figure it out now before it turns into a problem.

[greg g]

If you have the driveshaft with the ball and trunion u joint on both ends, remove it, swap ends. See if your  noise goes away or changes.  Before you remove it mark the flanges so you can replace it to its original position if you need to.  These setups will over the years make one joint dominant, especially if your use and loading of the car never changes, meaning one will do most of the movement and work, the other will remain it a static position.  Swapping ends will cause them to get out of their ruts and move through different patterns in different places along the trunion.

This might moderate the noise, change its frequency, or better isolate it's source. Or help to point you elsewhere for the source of your squeek.

[kencombs]

Check the rear bushing in the trans for wear.   Long shot, but if it can move at all the movement will be different if the trans output is driving it vs the driveshaft driving (power vs coast)   That could cause a closely adjusted park brake to drag.   Long shot as said but possible, or maybe the brake is dragging all the time and a tiny movement causes the sound?  Centering those bands is a pain sometimes.

[Bryan G]

Thanks for the ideas! I didn't feel up to crawling underneath today, but I'll give it a go soon. Ideally I can get it up in the air and run it, but we'll see. I have a couple theories, based on some of the thoughts here. I'll report back when I figure it out.

[dpollo]

I had this problem with a 70 000 mile 55 Plymouth.  Removed the rear universal joint cover and placed a washer on the centering pin

This loaded up the tension on the shaft and the squeak went away.  The same noise can occur on braking as the angle of the joint changes.