Sealing transmission pan

It was interesting to see that Mopar RTV that had been updated from an AA suffix to now an AD suffix. I'm familiar with that - some of you may know what Threebond 1217-F RTV is that has also ratcheted up the suffix through the years as well.
i use a lot of threebond (a carry over from two wheeled work) and that stuff certainly works great in specific applications. i'm always hesitant to recommend it for anything that requires "frequent" service or inspection because it's such a bastard to clean up.

but when it absolutely, positively has to seal and you've tried everything under the sun? it's time to break out the hylomar...