When I put the XJ in 4lo and give it a lot of throttle, I get a bang in the drivetrain. Sounds like its coming from the front left. Any ideas?

 

Not sure I can help but I was getting a bang under my cherokee and it turned out to be the exhaust banging on the trans cross over bracket..

 

How were you able to come to that conclusion?

 

It's a pretty common issue with Cherokees that see any amount of snow and salt. Doesn't sound like that's your issue, however.

 

Check your hub locks. I'm not sure why this would only happen in 4lo only.

 

I'm still having the problem but I think its a motor mount. I have the entire front end of the jeep torn apart though so I can't easily check it. I think it was only happening in 4lo because of the added torque it puts on it from reving much faster.