Hi Guys,

I've got a '91 K1500 4x4. It has the 5LM60 Manual Transmission. It was originally a 305, but I just built a 350 and changed it over to a carbureted system. While I was at it, I put in a new flywheel, clutch and throw-out bearing. After driving it for a hundred or so miles for break-in, I started to get a high pitched metal to metal type of squeak coming out of the transmission. It's a rotational noise. Something rotating is squeaking. I continued my break-in, but I couldn't tolerate the noise coming out of a brand new motor. I took it to a shop and asked them to change my throw-out bearing, clutch release fork, and the pivot ball. He did so. I picked up the truck and within 2 miles the noise was back. I didn't bother taking it back to the guy because a) it wasn't his fault, and b) I didn't really care for the guy's work. So now I have the transmission back down and I'm taking a look for myself to try to find what is making that noise. Come to find out, the new throw-out bearing already has wear marks on it. I literally have about 100 miles on it. There is no way that should be happening.

Keep in mind, I didn't have this noise when I had the old 305 in there with the old clutch, flywheel, and throw-out bearing. I guess what I'm asking for here is, what could be causing the throw-out bearing to make noise this quickly? On two separate brand new throw-out bearings?! Is it possible that the aftermarket clutch that I put in isn't exactly perfect? The flywheel? Pilot bearing? Is it possible that the throw-out bearing isn't making the noise at all? I'm at a loss here guys. Any help would be greatly appreciated. Thanks!

Brad

 

I don't see anywhere where you mention replacing the pilot bearing. Has it been replaced? The pilot bearing being worn could cause your problem. Inspect it for wear. Rotate the throw out bearing by hand and see if it rotates smoothly. Where on the throw out bearing do you see the wear?

 

I did change the pilot bearing, but it could still be junk because it didn't go in very easily. It's possible that I screwed that up. The throw-out bearing has a couple small dents around the edge of the bearing toward the face of the bearing that rides on the pressure plate. I don't know how those dents got there, but they are there. Also, the bearing moves a little bit front to back. Basically if I hold the bearing with one hand, I can move the bearing and hear a "click" when I press on it from the pressure plate side to the clutch fork side. I'm not sure that it's supposed to do that, but I'm thinking it's not. I think it's pretty clear that my noise is coming out of the throw-out bearing, I just can't figure out why they have both become junk in less than 100 miles each. I'm starting to lean in your direction though on that pilot bearing. I think you might be on to something there.

 

Did you ever figure out what was causing your throwout bearing to go bad so quick.

 

Ended up being the pilot bearing creating the noise.