Originally submitted by T:
When General Motors first invoked hydromatic gearboxes decades ago
they made the conscious decision that gear shifts would be imperceptible.
Part of the process of making the changes so smooth was the oil which is why Dexron oil was developed for them.
Not using the recommended oil in these gearboxes will result in "bang" shifts, gearchanges
that are noticeably abrupt and which reduce the life of the band and clutch packs.
The Trimatic was introduced with the LC and HG model range and used a cable kickdown mechanism.