Hey all! Today while driving my 1998 Cherokee Sport, I noticed a rattling sound coming from underneath the Jeep. It usually only occurs when I start to accelerate, and is completely gone after I get up to speed. Sometimes it makes that sound for a couple of seconds, other times it's about ten seconds. The car drives normally, and occasionally I noticed some kind of grinding feeling that I was able to feel at the steering wheel. Like something was grinding and it traveled up through the steering wheel. It WILL NOT do this when idling no matter how much I rev it, or parked or in reverse, only in drive and only when I start accelerating. My first guess would be something fell into the transmission bellhousing somehow, but I don't know how to check. The crankshaft position sensor and the ignition coil were just replaced today. Any ideas? Thank you!

 

Some info I should add:

It does not make the noise when I put it in drive and let the car go on its own.
I pushed the brake down and then gave it some gas and it does not make the noise then either. I have no idea what it could be. It's like it's coming from the center of the vehicle from underneath.

 

I'm gonna go with transfer case linkage. Try fiddling the selector when you here the noise and/or get underneath and lube it up.

 

Thanks man, I'll check it out here in a bit. I thought of a way to describe the sound better, it's like if you took a circular piece of metal with teeth on it and spun it against a metal rod. Like a metal on metal rattle/tick.

 

Coincidence? Change CPS, now a rattling noise!
If i didn't know any better, i'd say one of the CPS bolts fell into the bell housing.
Not hard to do.

Did you change the CPS yourself or have a shop do it?

 

A shop did it, I was going to do it but the lower most bolt was completely seized and I didn't have the means of getting it out. I took the top bolt out on my own but I took it out by hand once it was loose enough so it wouldn't fall in. Maybe the shop accidentally dropped a socket or something in it

 

I just got underneath it and checked the inspection plate bolts on the front of the transmission, those are good. Could probably take that off and check the flex plate itself at some point. But I checked the transfer case linkage and shifter, nothing was loose. Checked drive shafts and they don't have any play other than the very very small amount you can turn them by hand. Gave my cat a few smacks and I heard some rattling sort of, except it wasn't at the cat. It was behind it on the muffler. I hit the muffler a couple of times and every time it makes some kind of rattle noise. Could this be it? I'm not sure if it would create the noise I described. As it's more like metal teeth hitting something.
I also checked the bolts and hangers for the exhaust, nothing was loose there either.

 

A piece of substrate inside the cat may have broke loose and found its way into the muffler. Only way to know for sure is to pull the muffler and take a look. Give it a shake, even. For example, when a heat shield breaks loose at the cat (just one tiny weld), it can sound similar to what you describe. Like a baseball card in a bicyce spoke. Or dragging a stick against a wooden picket fence while you run.

 

So I just checked the heat shield on the cat, guess what?
The bugger lifts right up off of it! I don't have to do anything but use a finger to get it to move and lift up.

 

After fiddling with the heatshield and moving it around a little bit the rattle has stopped, so I believe I found the source of it and a temporary fix. If it comes back I'll try clamping it down with some hose clamps.