Stopping a common Rattle
One of the common problems with Jeep Cherokees withe AW4 automatic transmission is that the flex plate bolts back out after a while.
The flex plate is bolted to the torque converter with four relatively small bolts. With age and time they get loose.
The noise is often diagnosed as a rod knock or something more severe and the Jeep gets sold cheap or scrapped. If all the bolts fall out the Jeep will have no drive in all gears and be misdiagnosed as a transmission failure.
Inspecting the bolts is a relatively easy task. They are hidden behind a small metal plate at the bottom of the transmission bellhousing.
This little plate is very well secured to the transmission. It had two large bolts with 18mm heads and two smaller bolts with 13mm heads.
If your Jeep is like most, this area will be covered in mud and oil from a leaking rear main seal. So it may take some digging to find the two small bolts.
One big issue with this task is that the bolt on the left side of the transmission will not come out unless you also remove the exhaust pipe. However for just an inspection and tightening, you can get by without totally removing this bolt. Just loosen the nut so the bolt can be moved back against the pipe.
With the other bolts out you can pull the plate back enough to see the flex plate bolts and get a 15mm box end wrench on them to snug them up as necessary. If you want to work in a torque wrench or put on some locktight, you will have to remove the exhaust pipe.
Once the bolts are tight, you can turn the transmission with the wrench on the bolt. There is just enough room to bring one bolt to the bottom and be able to access the next one at the top of the opening. There are four so keep count and you will know when they are all checked.
Inspect the flex plate for damage while you are there. If the bolts have been loose for a while the holse my be elongated or the plate cracked. If this is the case, you will have to remove the transmission to replace the flex plate.