ZF 8HP tagged posts

Last week I have discussed the GM 8AT and the ZF 9AT, today let’s take a look at the Aisin AA80E, which is used in the Lexus IS350, GS350, LS460, IS-F and the upcoming RC-F.

Unlike other longitude mounted 8AT such as the ZF 8HP and GM 8L90, the Aisin transmission uses compound planetary gear sets. A compound planetary gear set is a planetary gear set that has multiple sun gears or multiple ring gears. There are different types of them, the one we are interested in is called the Ravingeaux gear set, which has two sun gears, two planet carriers and they share one common ring gear.

One Ravingeaux gear set can provide 4 forward gear ratios and also the neutral and reverse.

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Last time I showed you some interesting facts about the ZF 9HP transmission. Today I am going to talk about the latest GM 8L90 8-speed automatic transmission, which will be used on the 2015 Corvette.

Please do not be confused with the Cadillac CTS 3.6 V6 trim’s 8-speed transmission, that one is not the 8L90. Instead GM sourced it from Aisin and it is a completely different design.

First I would like to show you the structure diagram of the 8L90. The drawing is from the patent GM filed with the US Patent and Trademark Office several years ago. As expected in a patent document, the drawing looks terribly complicated...

Last year, Mercedes-Benz debuted its 9 speed transmission (called 9G-Tronic) in its European market E class sedan.

Although with the same aluminum made torque converter bell housing, compared to the current 7G-Tronic, this 9G-Tronic transmission changes to use magnesium alloy to construct its main casing, which is lighter and retains the same strength. The transmission oil pan is made with plastic though.

However, there is no dramatic difference of the mechanical shifting parts between the 9G and 7G transmission. Both of them have 4 planetary gear sets and 6 shifting elements (3 multi-disc clutches and 3 multi-disc brakes)...