Been working on my jeep, and today I drove to the auto hobby shop on my base to try fixing a freeze plug on the back of the block because it's leaking coolant and I'm pretty sure that's what it is. On the way there I noticed it shudders when stopping and stopped while in drive. It feels like its the transmission but I can't be sure. If I put it in neutral or park it stops.

 

Could be a bad transmission mount. I just changed my. It helped with some noises I was hearing.

 

That's the rubber part on the cross beam underneath right?