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FAUEE 03-30-2013 10:21 AM

Mechanical/Driveline Experts - 2 speed PTU?
So I was thinking about this new 2 speed PTU a bit, and based on my previous experience, thought that this didn't make a lot of sense.

Correct me if I'm wrong, but the PTU only receives "half" (this could be varied so it might not necessarily be half at all times, could be less) of the output of the engine, the first "half" is diverted to the front wheels. So having a 2 speed PTU would only engage a low range for the rear wheels, as the front wheels were never involved in this gear changing.

Compared to a traditional TC setup, the TC sits before the rear wheels in the driveline, and so it splits up power before hitting a set of wheels, allowing all four wheels to be put into low range.

This is based off previous experience with an AWD vehicle that was FWD based - the FWD models can have the same driveline, and they just don't bolt on the PTU, rear driveshaft, etc. While it seems like it could be possible to somehow put the PTU in line before either sets of wheels get power, that seems like it would be horrendously expensive to allow for a 2WD and 4WD model.

Is my thinking right here or do I need more coffee this morning?

Marlon_JB2 04-01-2013 10:43 AM

Re: Mechanical/Driveline Experts - 2 speed PTU?
More coffee. Read: 2014 Jeep Cherokee, the Liberty-replacement SUV: can it measure up to its legendary namesake?

This isn't your traditional PTU setup. It's entirely different and new. Might as well call it a transfer case...

loveracing1988 04-17-2013 02:34 AM

The ptu has outputs for the front 2 wheels and the rear axle, it is the same no matter what ptu you get, either the 2 speed or the 1 speed, the 2 speed just adds a planetary gears et for gear reduction. A lot of ptu's are the same, gm's epsilon program, gm's small car ptu's. The difference is the cusw ptu has a disconnect in it where as the others don't.

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