Unfortunately I have no personal experience on this one. My factory undercoating is still there and in good shape and in Texas, will probably stay that way for eternity....
In anticipation of moving to Pennsylvania, my buddy with an LJ pulled his trans to change the clutch and do some other stuff down there and while he had it out, used 3M Pro Undercoat. He is happy with the results. He cleaned the underside and sprayed it right out of the can onto the underside of his rig himself. Plan on probably 5 cans to cover everything, depending on how in detail you go and how thick you lay it on. I believe he used 6 cans on the LJ so maybe 4-5 to do the same coverage on the smaller short wheelbase YJ.
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