Don Verity says:

The oil pan on 727 transmissions can be quite difficult to get a good seal on. There are less bolts than on the iron TF to hold it tight against the pan rail. I start by making sure the pan is straight across the bolt holes. I do this on the edge of the bench with a ball peen hammer. I use a 12 inch machinists rule to check flatness. I then use my air grinder with a 2 inch 36 grit roloc disc to rough up the pan surface. The gasket needs something to bite to, so it doesn't squeeze out while torquing. Mixed fiber gaskets seem to work the best.

The next step is to bolt up the pan to the trans case without the gasket. Just snug up the bolts. Take a .010 feeler gage and see if it fits between the bolt holes. If it does, tap it down with the hammer. The gasket will take up and slight differences at this point.

Next, remove the pan and install the gasket. Do not use sealer. Torque the bolts to 8 foot pounds, and then to 13. Go around once more at 13 and you should have a leak proof seal.

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