so i read and searched all morning for posts but found no answer... My 08 4dr Rubi auto has a funny rattle noise (sounds kinda like a bolt rattling around inside something or metal on metal type rattle) I only have noticed it now that i put 35's on and no regearing....

It seems the rattle only happens when the jeep shifts up and the RPM's drop low... at that point, as i hold the accelerator at a constant to maintain speed.. something rattles... (Maybe engine with idle so low pushing bigger tires now?) just curious if anyone has a solid answer on what it is... I'm allergic to the Stealership unless its something major... Any thoughts or ideas will help...

Oh and i haven't been able to re-create it in park

 

I think I have the same problem you are describing. I also have an 08 Rubicon Auto. I still have the stock wheels/tires and have not regeared. Have added a CAI and Superchip, but the sound started before I installed them.

In my case, I'd describe the sound as a "jingle", kind of like car keys. I haven't done much investigation on the source of the sound yet, but it seems to only last about 3 seconds at most. Usually when I'm accellerating. I've tried rolling downhill in neutral with the engine off: no sound. I've tried rolling in neutral with the engine on: no sound. I've tried revving the engine in neutral and park: no sound. It only makes the sound when accellerating with the engine on and in gear.

Also, I only hear it when at a relatively slow speed. I haven't noticed it when at highway speed. Maybe because the ambient noise covers it up or the sound itself is not very loud.

So, no answers yet, but lets keep thinking about this.

 

Heatshields are quite prone to rattling. Check all of the heatshields (best when the Jeep is cool wouldn't want burnt fingers ) to see if any of them make a rattle when they are jiggled.

 

make sure the exhaust isn't close to anything as it moves quite a bit under load

 

Maybe engine overworking?

 

Sounds like detonation/pinging, put some higher octane fuel in it and see if it goes away. Will only do it under load, and will be more prone to doing it once it just shifted at low rpm like you said.. Added load of the 35's may do it, may learn itself as well. I'd start with disconnecting the battery (touch ground to positive once the ground is 100% disconnected). Reconnect it and drive it, toss some 91 in it for a tank and see if it goes away. Could be bad/crap gas as well.

 

thanks mike.. i'll give it a whirl.. you're scaring me with the ground touching the negative though.. i thought the ghostbusters said never cross the streams?

 

The automatics are notorious for wanting to shift prematurely. That puts too much of a load on the engine. I can only imagine what that would be like with bigger tires and no regearing. I had to have my engine replaced at 18K. When I got it back, the whole Jeep was a different vehicle. The transmission shifts like it's supposed to and holds the gear out as long as I have my foot in it. Come to find out, I didn't have the latest PCM reflash, and when they reprogrammed it from the engine swap, I got the latest one. The difference was literally night and day. I am actually HAPPY with my Jeep again. I would suggest maybe you go to your dealer and see if it has that latest reflash. It may not. If it does not, AND you have bigger tires without regearing, then that could be your whole problem. The trans is shifting into ahigher gear before it should and causing too much load on the engine making it detonate....at least that's what it sounds like you're describing.

 

I’m pretty sure that my noise isn’t detonation/pinging. It doesn’t sound internal to the engine/transmission. It almost sound like a bolt has backed itself out partially and the washer is jingling around on the bolt at certain RPMs. I’m definitely going to check the heat shields, exhaust, etc.

 

I think I have the same noise. I notice mine when the engine is over 2,000RPM and I'm accelerating or climbing a steep hill. It doesn't do it all the time though.
Funny thing is, it sounds very similar to the noise my ATV makes, which I know is a heat shield.