So I get the fuel economy "issue" but I'm way past worrying about that running E 70 right now...
But has anyone ever attempted to make our AWD system all time? Now that I've already had RDU replacement and I know exactly what it feels like when its bad I wonder if anyone has attempted this. If there was a way to eliminate the clutch system and use a solid "shaft" type system in place. Even now with my my new RDU when I hard launch I feel when the clutches slip and I hate it. It's sucks still having traction problems with our AWD systems and having it shut off when we need it the most. I wonder if it would be possible. I don't see why not.
I think if you had it on all the time the PTU wouldn't hold up.
I would like to be able to control it during launches when it really matters.
Maybe adjust the PWM a bit more.
Well you'd have to some kind of slip between the front and rear axles. Otherwise you'd end up with the same problem a 4x4 truck does locked into 4HI on pavement. Without the ability for the front and rear axles to spin at different RPM's there will be binding...problem is the front tires have to take the long way around a turn. The rear tires get to take a shortcut...therefore there needs to be a way for the front axle to turn faster then the rear axle to allow smooth turns.
For example, the AWD system Ford uses on the F150's like whats in my wife's truck. In 4A mode it uses a clutch pack inside the transfer case that is PWM by the TCM. It uses wheel speed sensors and pedal position and steering wheel angle plus about 100 other inputs to determine how much it can engage the transfer case clutch. By allowing slip at the transfer case around turns it eliminates the binding that would occur. Those same transfer cases in 4HI just simply lock the clutch at 100% DC all the time which causes the truck to act like a normal 4x4 truck in 4HI or even 4LO for that matter. Hope that makes sense!
Just to be clear, no clutch pack in the PTU, only in the RDU, and it is isolated from the gears, so the RDU fluid never touches the clutch pack.