Thoughts on Changing Transmission Fluid

[JCL]

By request, a summary of the adaptation capabilities of the ZF transmission. The easiest document to search on was the ZF patent, so here is one of the main ones. Related patents are linked on the page.

Therefore, the problem on which this invention is based is to make a method for control of a transmission of a motor vehicle available which, for each of the different influences which impair a gear shift, a separate adaptation can be carried out from which can be deduced the respective right reaction for an optimization of a subsequent gear shift.

Note that each shift is monitored, and then adaptations are calculated for an optimization of a subsequent gear shift. The system adapts, therefore, to each of the different influences which can impair a gear shift. Full details of what they measure and how those measurements are applied to the reference condition are contained in the patent. Pretty heavy reading, but some may find it interesting.

Brandon: I humbly submit that fluid condition as it changes over time is an influence which can impair a gear shift of a wet clutch pack (each clutch pack forming a shifting element). I think we agree that fluid quality over time is an influence. ZF got a patent based on adapting to each influence. Ergo, they are adapting to fluid quality, not by direct analysis of the fluid, but by measuring the performance of the fluid.

Patent linked here:

Patent US6569060 - Method for controlling a transmission of a vehicle - Google Patenter

Interesting side note again: The patent references a specific benefit of adaptive pressure control, namely that transmission manufacturing cost is reduced due to the ability to open up the manufacturing tolerance limits. Those tolerances can be opened up because the adaptive pressure control can handle wider tolerances than a 'dumb' system. We often think of modern vehicles as being much more complicated (which they are) and at the same time more precise, which would mean more demanding on things like fluid specs and quality over time. Here is a case where precision was reduced, intentionally. That intuitively fits with the transmission being more tolerant of varying fluid condition, which is where this discussion started.