In this episode, Transtar’s Dave Hritsko explains why the 4L60 2-4 band has so many holes in it. This transmission has been around a while and many people don’t realize when they have issues with the band burning up after a rebuild what the real problem stems from. The big hole allows for a constant
The secondary path of the charge/TCC-release oil is regulated to some degree by transmission parts within the confines of the converter. In some units, the charge oil is regulated by the orifice created between the raised area on the stator shaft (or support) and the impeller hub. In other units, it is regulated by restricting the flow of oil through or around the input-shaft bushing mounted inside the stator support. The Allison 500 series is a unique example because it uses both methods to regulate oil flow, as it both enters and exits the converter.
Most torque-converter rebuilders understand how oil flow within the converter harnesses engine torque and helps drive the vehicle. Unfortunately, many rebuilders have little knowledge of the many secondary paths and functions of converter oil flow.
The 4R100 has come by its flow problems honestly. It has inherited them from the E4OD.