In the automatic transmission racket, there have been new layouts and power flows galore lately. Your humble author has done a few articles detailing some of the more common designs in the North American market place, with the notable exception of the Aisin design. The design of a RWD manual transmission, on the other hand, is conceptually largely unchanged from the earliest 3 and 4 speed designs like the venerable M22 Rock crusher.This is not to say that RWD manual transmissions have not changed over the decades. The number of gears and torque capacities has increased, shift efforts have gone down, refinement has increased, which are all good things. This article provides some insights into the gear design and sizing for some of the more recent manual transmissions.
Tag: saturation dive
On the surface, there are many similarities between the ZF 8HP transmission family and the GM 8L90. Namely both use 4 gear sets, 5 shifting elements (3 clutches and two brakes), off axis pumps, and have roughly the same gear ratio spread at about 7:1 overall spread. The saturation dive is not about dealing with things that are on the surface. To be entirely honest as the details started to emerge on the GM 8L family of transmissions I suspected that it would end up being a ZF licensed design, the ZF 8HP after all is a very good design in my opinion. But the abstract of the paper that we managed to snag before SAE took it down revealed one very important detail – all 3 of the clutches were located in front of the planetary gear sets very much unlike the ZF design.
For those who don’t share my fascination with diving, a saturation dive is conducted at deep depths for extended periods of time at depths of hundreds of feet. I have read with bemusement the various “deep dives” that have been conducted by various publications into the workings of modern automatic transmissions. These deep dives tend to be more akin to splashing about in the shallow end of a pool. The name Saturation Dive is an engineer’s attempt at humor, namely to convey that this series of articles is much deeper than the stereotypical deep dives.