TH400 and similar units (4L80-E) Archives - Transmission Digest
Playing with Transmissions

Tech-support hotlines have been burning up for years with phone calls concerning rapid gear-train failure in GM TH400 transmissions after routine rebuild or repair. It’s time to address the issues that cause this and reverse widespread confusion surrounding gear-train setup on this and similar units. Today we will clear up the mystery in setting proper endplay for this transmission. If tolerances are not set correctly, costly comebacks can result.
Understanding these basic checks on the 400 will give you back-ground knowledge in setting build procedures that will be used with similar gear sets, such as 4L80-E.