Very interesting article about the ZF8HP!
What an amazing piece of mechanics
Quote from the page:
Chris,
The inertia inside an automatic transmission is actually quite low. Engine rotational inertia tends to range from 0.2 to 0.45 kg-m^2. For comparison, the 5th gear inertia is somewhere in the region of 0.04 to 0.08 kg-m^2.
So while fifth gear operation is complicated, the losses are not that bad. I would estimate the losses at 5th gear and 2000 rpm with 20 hp road load to be no more than 1.5 hp.
Please remember, even when planetary gear sets are along for the ride, they still contribute to the inertia.
http://www.thetruthaboutcars.com/201...eed-automatic/