4L80E & TH400 Tech.

[clinebarger]

I thought I would share some Tech for 4L80E & TH400 transmissions.
These units have very few weaknesses. But can be made better with a few mods.

Dual Feeding the Direct Clutches is hands down the best mod you can do.


From the factory the Direct apply piston is divided into 2 separate sections. In factory form, 3rd gear oil only uses the smaller of the 2 sections to apply the Direct clutches.

However, Reverse uses both areas to apply the Direct clutches.

The first diagram is D3/D4...Directs clutches applied.
Second diagram is Reverse.