Mystery Grinding Noise - Any Ideas
 

Hi All

I have a 1992 extended cab pickup 4X4 with a 3VZE under the hood. It has just started to make a grinding rattling noise while decelerating, and only when decelerating, but not every time I slow down. While the noise is going it is consistent (ie not clunk, clunk, clunk) Almost like bailing wire caught up on the drivetrain, but there is definitely nothing caught under there.

It sounds like it is coming from the drivers side rear of the engine compartment or possibly the front of the transmission. It sounds closer and lower than the valve/ injector noise but I am having a very hard time pinpointing it (only makes the noise while moving so I can't get out and listen).

Any ideas of what it could be? What does it sound like if the main clutch bearing is going out (the one that is not the throwout bearing), or a crank shaft bearing?

Again the noise happens:
-Only on deceleration
-Only with the clutch out (edit to clairify - when the clutch is not pushed ie the engine is connected to the transmission)
-Intermittently (about ever other time I slow down)

Probably unrelated, but it does have an exhaust leak and the O2 sensor is throwing a code 21. Guess I get to pull that apart this weekend too.

Thanks for any ideas.

If you mean the crankshaft in the engine, it's not that. Bad engine bearings lead to distinct knocking noises.

Other than that, sorry I can't help you except to say that it sounds like it's probably something in the tranny itself.

it could be the throwout bearing if it is when the clutch is engaged. i could be wrong but thats all that came to mind

messed it up posted below

engine and clutch parts usually make the same noises driving or sitting still. throw out bearing rattle anytime the clutch is engaged. you say only during de-acceleration. that means something that turns, in the drive line. inspect: u-joints, carrier bearing, speedo cable, hub bearings, diff play, front hubs can fool ya, they can "echo" all through the front end trans area. does 4wd make any difference? Does hubs locked or unlocked make any difference? It all helps to narrow it down.

Thanks for the ideas. The hubs seem like they could be a likely candidate, however I have only been driving in 2WD since this started. I'll try locking the hubs and throwing it in 4WD and see what happens. I hope the transmission isn't about to give up the ghost.

I think I had a brain fart writing my original post - it happens when the clutch is out, not when engaged (foot off the clutch). I was visualizing the clutch engaging the connection between the tranny and engine.

I know this post is a little outdated, but did you ever find out what that noise was? I am having the same problem and it only happens when I am decelerating from a faster highway speed. Sounds like a grinding noise. Any help would be much appreciated. I am about to put a new 22re in it and will be replacing the clutch which is what it seems like it might be, but not sure

Believe it or not it was caused by a loose exhaust bracket. The clamp holding the exhaust to the bracket that comes off the transmission had loosened up, and would somehow reverberate though the transmission at a certain RPM range, only when decelerating - it sounded nothing like a typical rattle. Not sure if that is going to be your problem, but it is sure an easy fix if it is.

I am currently experiencing this same problem, Only when the engine is warm and only when I am decelerating. The other day when brought home my boat, I drove about 30 min with it behind me and when I finally got to home the noise was so loud it would almost eco off the houses. I seriously expected to have something explode or rip off my truck, but after my truck sat for a little while the noise stopped. I assumed it would be coming from my transfer case but after I read your post It all made sense. It sounds like someone is holding a grinder on the heat shield of my exhaust. My question to you is where exactly is the bracket that your speaking of? I got under my truck last night but did not see anything right off hand (although I didn’t have much time to play with it). Is there any way that you could perhaps shoot me a picture of what you’re talking about?

There is a bracket attached to the transmission housing that has an muffler clamp attached to it that secures to the exhaust pipe. It should be mounted right where the transmission bell housing meets the motor and from there to the pipe.

I am not around my truck, so I can't get a pic for you but Crtzlow gave a pretty good description. It should be the only thing touching the exhaust between the manifold and cat. Then clamp on mine had sipped off and was sitting next to the catalytic converter. If it isn't there maybe it is a heat shield or something else coming loose.

I had the same thing happening to mine and the rear diff fluid was leaking and low. I replaced the the rear seal where the spline goes into the diff and changed the fluid and it cut down on the grinding noise upon deceleration tremendously.

It was the rear differential, but due to acoustics I guess, it sounded like the transmission.

Oops.. For some reason the video file is invalid. I’ll see if I can’t convert it to something that will work.

ok here you go
http://www.youtube.com/watch?v=AmC5A...ature=youtu.be