VW Transmission Question (mileage, buy, engines, replace)

[TCMaster]

I was just reading about the VW Phaeton, and I read that the V8 came with a 6 speed auto, and the W12 came with a 5 speed auto. Why? Shouldn't it be the other way around? Isn't a 6 speed better?

[ferretkona]

The 5 speed is likely built for more horsepower.

[Innovator831021]

REALLLLLLY powerful engines have a 2 or 3spd behind them.

[stanman13]

It's all about keeping the engine within the power band. The 12 cyl likely has enough torque over a wide enough range that it doesn't need the extra gear. More gears for gears sake isn't automatically (pun intended) better.

[M3 Mitch]

I'm guessing here, that the external envelope for both transmissions was the same, the 5-speed can have bigger (wider) gears, clutches, etc. which it needs to cope with the V-12's torque, said torque means it does not need as low a first gear, and/or can have bigger gaps between the gears (ratio-wise, not physical space) for about the same or better performance.

[TCMaster]

Wouldn't a 6 speed get better mileage?

[M3 Mitch]

Originally Posted by TCMaster

Wouldn't a 6 speed get better mileage?

Theoretically, if the ratios were selected to optimize mileage, probably it would. But I think the average V-12 buyer, at least people who buy them new, don't care that much about mileage.

That and VW would prefer not to have to replace trannys that blew in the warrenty period, etc. etc.

Again I think the point of using a 5-speed was to get physically bigger, wider gears and bigger clutches into the space available, or, even more likely, they had a 5-speed design available that would take the V-12's torque and the 6-speed design wouldn't.