89 XJ 4.0 auto 4x4 111,000 miles.

Quick update. Since changing plugs, wires, distributor cap, rotary button, cleaning TB, & oh yeah changing those God aweful melted battery cable wires, that luckily did not catch fire, the jeep has been running probably better than ever as far as just running.

I still have the exhaust pipe knocking at the cross member. Really do not know why as no hangers are broke, and my transmission mount is only a year old. I do have a very small exhaust leak near the cross member and it certainly knocks worse when cold so probably just need to spot weld that hole first off. That's not what this about though but I hate a knocking exhaust.

I am still wondering what this noise is when shufting from R to D and vice versa. Posted a video down below. Hopefully you can hear the sound I am talking about. Any suggestions & thank you. Just thought I need to try this with the jeep off.

https://youtu.be/0zauD88-JnQ

 

Check your U joints. Might just be slop there.

 

other things to check would be control arm bushings, brake caliper bolts, leaf spring bushings/shackle bushings and rear drive shaft u-joints. also check front driveshaft and axle shaft u joints, but in the video you only have it in 2wd. my guess would be control arm bushings.
but don't rule out other things like exhaust hitting cross member, as you torque your engine/trans as it cycles from drive to reverse, also motor mounts/trans mounts.

so, as you can see, it could be a number of things. so you just gotta get someone to either do the shifting or head poking, but just get under there and start looking.

 

My dad had a way of checking driveshaft u-joints that's kind or funny, but works. With the trans in park, or a manual in gear, rock the vehicle back and forth with your hands on the bumper. You may have to put your back into it. Bad u-joints will ring loud enough to hear them. Just something I remember from my childhood.

 

If you have a manual, put it in gear with the engine off please.... Hahahahaha....