TCI 278000 GM 4L80E/4L85E Cast Aluminum Deep Trans Pan

This is the TCI 278000 cast aluminum deep sump pan for the GM 4L80E and 4L85E. It replaces the thin stamped-steel factory pan and drops the sump roughly an inch and a half deeper, adding about two quarts of extra fluid. More fluid plus the cast cooling fins means the trans carries more heat away from the clutches, which is what you want behind a towing, turbo, or LS-swapped combination that runs the 4L80E hot.

The casting is far thicker than the stock pan, so it stops the flex-and-weep leaks that stamped pans develop around the bolt flange, and it stiffens the bottom of the case. It ships with a gasket, stainless steel hex hardware so you are not reusing rusted factory bolts, and a magnetic drain plug. The drain plug is the real day-to-day win: you pull the plug to change fluid instead of dropping the whole pan and fighting a full sump of ATF.

Note the internals. The pan uses cast pedestals that the standard filter rests on rather than a filter extension, and TCI includes two filters of slightly different heights so you can match the one that seats correctly against the valve body. Measure flange-to-filter before you button it up.

Fitment is the one thing to check first. On some 3/4-ton trucks the factory crossmember sits close to the sump, so on a lowered truck or a 2500/3500 chassis confirm crossmember clearance before ordering, or plan to loosen the trans mount and tuck it in. On most 4L80E swaps and standard-height applications it bolts right on.