When I start it up or put it in park the cherokee will start vibrating and it sounds like knock (I really hope not) but when I put it in any other gear it stops immediately. I noticed there is a switch one for power and one for comfort... What setting am I suppose to have it? I assume comfort since I am just driving normally with it.

 

it sounds like you have a part contacting something else causing the vibrations. especially if it only happens when you are parked. on my truck, the tail pipe used to vibrate against the leaf spring bolt in park and would go away when i drove it.

on the trans, that switch changes the shift points. for what its worth, i drive with mine in power and in the later models, the trans was just hard wired into the power mode.

 

Thanks I will take a look at it.

 

any more info?

can you feel it anywhere? i have the same thing going on.. i can feel it on my shifter and the 4x4 one too.. what about off ldie too. can you tell where its coming from?

mine is the trans mount. when i push my tc with my foot it makes the same knock ( with the truck off )

hope this helps

 

Mine has a similar problem that I've been trying to track down for a year or so now. [Although to be fair, I haven't tried very hard; it's been doing this for 65,000 miles, and I'm not dead.] My sound is exactly like the rattle you'd hear if the catalytic converter shroud were rattling...except obviously the XJ doesn't have one! [The shroud, that is.]

I'll check my TC with my foot and see if it makes the same noise. I wouldn't be surprised if it were my transmission mount.

 

Could be a vibration dampener going bad. Mine did the same thing, when I looked at it, half the rubber inner ring was gone. Replaced it and my vibration in park went away. Just a thought.

 

I assume the vibration damper is on the motor mount right?

 

Nope. Large pulley on the snoot of the crankshaft. But I'd also check your engine/tranny mounts as well.

 

There's a thread already posted on this forum with some good info on the crankshaft pulley/vibration dampener replacement. I was unfamiliar with the terminology, other manufacturers call it a harmonic balancer. Most of the repair shops use that term also. It sounds so much more exotic and expensive. If you search crankshaft pulley, you'll find the post. Autozone sells the part for about $60. It's not nearly as difficult a job as I had imagined. I changed one out on my 95 Cherokee. Took about 2 hours.

 

x2 on the motor mounts/tranny mount being loose.

 

+1
Mine does the exact same thing when in Park. I would check that first.

 

My jeep did this recently, but I am pretty sure I broke my U-joint on my lovely dana 30.