There was no way to know back then how popular the 400 would become with many groups of car owners. Truck owners of the 1500, 2500 and 3500 series trucks loved them because they were durable. Hot rodders and drag racers fell in love with the 400 because of durability benefits and how well suited it was for super fast and hard shifts. A drag racers dream.
As I mentioned in a post on the 4L80E, the 400 is the 3 speed section of the 4L80 transmission. When you have a product that is so successful, why not use some solid technology from such a successful source? The 4L80 is becoming a legend as the 400 has become.
To a transmission person this may be interesting, although a non tranny person may derive some satisfaction knowing the T400 operates a bit different than a 3 speed automatic transmission that uses a band for 2nd gear. The T400 uses a clutch pack for second gear. The beauty and life improving benefits from having clutch plates over a band for second gear is as such.
Clutches do not have to release before the 3rd gear shift can be made. A 2nd gear band has to release before the 3rd gear shift can occur, or a tremendous bind up (you might think someone hit you from behind) happens. The 2nd gear clutches in a clutch type (2nd gear) transmission do not have to release to cause a 3rd gear shift, thus a cleaner more efficient shift which translates into more life.
Enough mumbo jumbo, rebuilt T400 transmissions are a super deal, good enough to make looking for an old one not cost effective or a good value. T400 transmissions were discontinued in the early ’90’s, so locating a used one that has life left in it is not very feasible.
When you consider used in this case as being very used since they have been out of production so long, you are filling a short termed stopgap at best. For seemingly hardly any more cost buying a rebuilt T400 for your 3500 series Chevy truck will cost less than you expect and exceed your expectations by a mile. Read some of the testimonials on GotTransmissions.com home page if you want more .