How to replace a flex plate in a 1992 jeep cherokee

wrong flex plate ---if starter shimmed wrong shim --

I am pretty sure that the crank sensor is what fires the injectors. Make sure the sensor is good and that it is receiving the signal from the flex plate.

great but no transmission stated.
a/t
42RE? or 45RFE?
check bolts on flex plate? (TC flex plate to fly juncture)
seem like a torque reaction , caused squeak, ( i cant hear it so...)
the mounts, spray them all with silicon spray, try that first before
a new $2-3000 trans..
U-joints? spray them next, if now gone ,bingo>
keep in mind noise can telegraph. that means
noise can travel far , from origin. fooling any one with a stethoscope.

Other possibilities can be bad trans mount, heat shied on cat or bad catalyst conv. Or engine mount leaning on frame

Did you re-use the flex plate? A cracked or broken one can sometimes sound like a rod knock.

As long as both are 4.0 engines it will work. You will probably have to change some sensors and use the wire harness from you old engine. Also you may have to change the intake. You may also have to change the flex plate or flywheel from the old engine. Be sure to double check this stuff. Also the engine mounts might be different but they bolt on so you can change them with the old ones.

Four things can give you a knocking noise. 1. failed rod bearing 2.failed main bearing 3. Bad piston wristpin 4. broken flex plate (auto trans)
If It's a bearing, likely you are seeing lower than normal oil pressure. Any bearing repair requires the pan to be dropped but to do the job correctly requires engine removal, crank re-grinding or replacement and oiling system cleanout (expensive). Wristpin (piston/rod assembly) can be serviced without engine removal but pan and cylinder head need to be removed. Flex plate is pretty much a trans remove and replace, with new wheel.
Only a good experienced tech can differentiate between the noises so I suggest you seek aid in your diagnosis, though, if either bearing or piston is the problem I'd likely find another engine before considering the repair.

To remove crankshaft, engine must be removed from vehicle. It is bolted to the flywheel/flex plate of your transmission. Even if you found a way to remove it, it would be really difficult to replace it correctly. If you are going to replace it due to a bearing failure, keep in mind that debris from that failure likely has migrated into oil galleys and is waiting there to damage new bearings. At the very least all passages should be blown out with high pressure air, preferable is to strip engine down and also check cam bearings which may also be worn from pressure loss during failure and debris.
good luck!!

try autozone.com to see if they have your car listed for diagrams pictures and step by step instructions if your car is not listed then try your local library they have all the car manuals and even copy them for you

try www.autozone.com to see if they have your car listed for diagrams pictures and step by step instructions if your car is not listed then try your local library they have all the car manuals and even copy them for you