4.0L HO or Aw4 vibrating/knocking

[tj00xj91]

I have a new to me 96xj. I got the jeep with a blown 4.0l. I got another 4.0 from someone who said it came out of there jeep and it was supposedly running fine, well its not. Anyways the issue is motor starts and runs smooth until 1000k-1800k RPMS, then something knocks. It does this in neutral, park, and in gear. Runs smooth lower than those rpms and runs smooth with higher rpms. Also I did have someone else hit the gas while i climbed around underneath and the knocking seems to be coming from the Aw4. The motor seems to be strong and pulls hard as well as the tranny seems to shift and hold gears fine. Is it the tranny or fly wheel? or What do you think?

Have already checked:

1. Exhaust to see if it was hitting anything and its clear.

2. Double check to make sure the torque converter is tight.

3. I currently have the fly pulled out and looking at it seems to not have any cracks.


Now what to do? I have a fly and torque converter from another 4.0l but I dont want to install this if it is something else in the tranny. The tranny seems to shifts fine and hold the gears fine in the limited driving I did do before pulling the fly out.

 

[tj00xj91]

ttt

 

[90Blue_XJ]

Did you install them as a unit or were they married together after the engine was installed? I ask because the flexplate is difficult to get torqued very tight while on an engine stand, also the bolts that bolt the converter to the flexplate, when loose can make a knocking noise.
I seriously doubt that anything inside the AW4 is knocking itself.

 

[j33pownr]

My 92 4.0L has had the exact symptoms for almost a year now. Its my DD so I havent pulled the flywheel or aw4 since it drives fine like you stated. I have also inspected and tightened the flex plate like you to no avail. In the last few months I have replaced most of the sensors due to another issue (iac,tps,o2,cam,crank) and the noise still persists. The only thing I havent done is replace the injectors. The only reason I say injectors is because the vibration feels like a slight miss fire where the last two injectors arent getting a good voltage signal in that certain rpm range and I know the new sensors are good.

Since you have the aw4 and flywheel out with everything looking good, can you start it and run it through the rpm range without the aw4 attached to eliminate it from the problem if the knocking still continues?

 

[tj00xj91]

Did you install them as a unit or were they married together after the engine was installed? I ask because the flexplate is difficult to get torqued very tight while on an engine stand, also the bolts that bolt the converter to the flexplate, when loose can make a knocking noise.
I seriously doubt that anything inside the AW4 is knocking itself.

I installed this motor, fly, and torque converter to existing tranny. I havent tried to install extra fly or torque converter that I have. I did not pull the motor out of the jeep, so i will be installing the fly with the motor in the jeep. All the bolts where very very tight when i removed the fly.

 

[tj00xj91]

My 92 4.0L has had the exact symptoms for almost a year now. Its my DD so I havent pulled the flywheel or aw4 since it drives fine like you stated. I have also inspected and tightened the flex plate like you to no avail. In the last few months I have replaced most of the sensors due to another issue (iac,tps,o2,cam,crank) and the noise still persists. The only thing I havent done is replace the injectors. The only reason I say injectors is because the vibration feels like a slight miss fire where the last two injectors arent getting a good voltage signal in that certain rpm range and I know the new sensors are good.

Since you have the aw4 and flywheel out with everything looking good, can you start it and run it through the rpm range without the aw4 attached to eliminate it from the problem if the knocking still continues?

Well i dont see how i can start it without the fly or tranny connected to the motor. The starter mounts to the tranny housing i do believe. I am out of town at the moment so I cant really say for sure.

 

[j33pownr]

Yea I know you needed the flywheel to start it but I am a bone head and forgot about the starter mounting to the tranny .

To achieve what I was asking you could remove the torque converter but bolt the fly and starter up. Then that would eliminate the tranny from the equation.

 

[tj00xj91]

Just to let everyone know in case they have the same issue. I removed the old flywheel and installed another from another motor I had and the Jeep runs great now.

 

[j33pownr]

Thanks for the update.