Knock/ Rattle? confused...

[SpoiledBrat]

i have an '87 XJ, 4.0 I-6, i have a knock/ rattle coming from what seems like the tranny, or maybe the exhaust? it's not in the motor, it doesn't knock all the time, and it doesn't speed up when accelerated, and only does it in park or Neutral. seldom will it knock while in gear. it's more of a banging sound than anything. it's not a rattle or tap, and is not from the motor. it sounds like something may have come loose, but not sure? any help or input would be greatly appreciated.


My Jeep Doesn't Leak... He Marks His Territory...

NOT ALL GIRLS ARE PASSENGERS

[4.3LXJ]

You likely have an exhaust pipe rattle. Check your motor mounts and transmission mount for excessive play. Also check your exhaust hangers too.

[89Laredo]

Maybe flex plate bolts, but that would be a constant...

[SpoiledBrat]

Steve, i checked all mounts and exhaust when the sound first started, i didn't notice anything lose... maybe check it all again.
Dylan, flex plate was my first thought, but it's nice and snug. :)
Thanks!

[prerunner1982]

Since it only does it in park or neutral at least you are able to get under and get a closer look. Hard to do that if it only did it while moving. :)

And Welcome to our addiction. Is there a cure for this addiction?....I don't know, nobody here is actively searching for one. :)

[89Laredo]

Use a piece of dowel held to your ear to help find it.

[prerunner1982]

Use a piece of dowel held to your ear to help find it.

The redneck auto stethoscope.

[gary63]

check your u-joints you may have one with a bad needle bering if so most likely it is one that is close to the t-case. if you have just 1 or so going bad or broken it will make nose when the driveshaft has no load and then magnify though the jeep.

[Carves]

X 2 on checking what the others have mentioned .... and maybe also ... the bash plate clearance for the transfercase.

I had a similiar issue caused by a bent crossmember ... and compounded by a worn out gearbox mount.