I just stripped my drip rails down to bare metal this evening with a high speed grinder and small wire wheel. It is clean and shiny. What kind of prep should I use before going with the new seam sealer? Should it be sanded to give it some tooth and then Prepsol? I wonder if I should use POR15 under the seam sealer in case it decides to crack and leak just like the OEM sealer? Any thoughts here? Are you supposed to use primer under the seam sealer?

I always epoxy prime then sand and do my urethane primer and after it is sanded run the seam sealer. After the sealer drys a few days I reprime and then sand before painting. Be sure to get a flowable seam sealer that is activated and you won't have any problems. Duramix, Fusor, and Plastomix are a few brands that offer it.Don't use the old 3M one part sealer it is like the factory crap and will shrink and crack up.

How does the flowable sealer work on the vertical sections of the drip rail? Do you do it in two stages and tip the cab forward, on its nose, when you do the vertical, rear, section?

Just be sure to get the control flow and you won't have any problems.

i'll second the comment about the old 3m, the "fast and firm" is neither fast or firm, it could dry in 2 hours or two weeks, different every time, and it stays soft. its very close to the stuff that you put around a sink. i stick to my rule of not using anything that doesnt catalyze.

Do you guys mean the 3M Drip-Chek 8531? If so I had better return mine before I open the tube...LOL! I just realized that this is the one part so it must the stuff you are referring to. Someone told me that it worked great.