4L60 Archives - Transmission Digest
Hydraulics Fundamentals: Accumulators & Shift Feel

Accumulators and their circuits have been used for years as the primary method for controlling shift feel. These components are designed to modify a shift by essentially acting as a shock absorber for the fluid pressure that is applying a clutch, brake or band. Cushioning of this high pressure allows the apply component to engage gradually, instead of slamming on and rattling parts and bones alike.

Déjà Vu All Over Again

When GM introduced the stamped-steel drum for the THM 200 transmission, it presented technicians with some new challenges. The 200 direct drums would crack where the inner liner (where the piston lives) was joined to the outer shell. The weld that holds the two members of the drum together is subject to pivotal flexing each time the clutch is applied. Over time, this flexing action will cause a crack at the weld.