TOD discussion

[Tone]

I don't know if this has been mentioned in this thread but realize when you open the circuit to the clutch it is NOT in 100% 2WD mode, there is still plenty of torque going to the front wheels, enough to snap the front drive shaft when on a 2 WD Dyno - been there, done that. That is also a factor why gas mileage does not measurably increase with the current TOD disconnects out there. Good luck and I hope ya'll can make the whole thing work as planned.

[mbeach]

...but realize when you open the circuit to the clutch it is NOT in 100% 2WD mode, there is still plenty of torque going to the front wheels.

I did not know that.
I was hoping that it would be in 2wd until the VSS tells the TOD that the truck is moving faster than 5 mph.
That means that there must still be a mechanical connection somewhere.

I'll see what the PWM signal is at <5 mph vs. >5mph.

Also, there's a few suspect pins on the connector. There is a 4wd output at pin 3 that I want to look at in addition to the solenoid wire at pin 4.

[mbeach]

Eureka!

Please bear with me.

We are working on motion distribution NOT torque distribution.
We should be concentrating on torque distribution via the electromechanical clutch.

There is no axle disconnect on the VX, and the transfer case has no allowance for any 'freewheeling' of the front axle. The design of the transfer case is such that the front axle (and wheels) are ALWAYS driven at the same speed as the rear driving wheels. Rotational speed is NOT torque. Torque only exists when there is resistance to this rotational movement. This resistance is applied by two things: the electromechanical clutch, and the ball/ramp mechanism (see figure 3 and 4, as well as page 16-17 of the patent). The ball/ramp design of the coupling mechanism is NOT self locking UNLESS there is a control input. Resistance to movement (at the front wheels) provides this control input just as well as activation of the e-clutch.

This explains Tone's snapped driveshaft. The solenoid was deactivated, yet the speed differential between the front and rear axle was great enough to allow the ball/ramp clutch to force the rotor away from the connecting sleeve -this action transferred (almost) 100% of the available torque to the front axle and BOOM. Tone, did your dyno graph suddenly fall off just before your driveshaft went?

The E-clutch provides a means of modulating torque by applying measured resistance to motion according to a predetermined pattern.

Assuming that I haven't completely lost my mind, there is NO WAY that we will ever have true 2wd without an axle disconnect feature.
So, that leaves us with modulation of the e-clutch's holding power via PWM. This can be done only as long as both driveshafts are turning. If the front driveshaft should stop suddenly (like it is dropped into a hole under power), expect the ball/ramp clutch to do its work, regardless of what setting the manual TOD switch is in.

[newthings]

So, if a CV joint is broken and you have unlocking hubs and you lift the blue wire, the front diff will still spin the broken joint/axil?
Roy

[Maugan_VX]

Let me be the first in this thread to say....

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YAHTZEE!

[mbeach]

Newthings, I am inclined to say "yes." To tell for sure, one of our dyno jockeys could leave the drive shaft in and jack up the front of the VX during their next 2wd pull.

Maugan, if this is something that you knew for certain, please save me the trouble of figuring it out for myself. If it weren't for Tone's post, I would have completely ignored the ball/ramp mechanism, which would have led to big trouble had I decided to test my 'new' 2wd mode by doing donuts in the parking lot.

This doesn't mean that we can't modulate the clutch to go above the 15% that it seems to like (in '2wd') however.

It just means we can't have true 2wd. We might be able to use locking hubs to disconnect the wheels, but that driveshaft, diff and those axles will still turn.
I still want to pull the signals off of some wires to confirm this, but I believe that this (the mechanical connection) is certain and un-bypassable (?) in a non-SOTF transfer case.

There is a TOD Trooper in a friends' junkyard nearby...

[Maugan_VX]

I know not about the drive shaft issue.

All I know is that we're getting close to a dial on my dash for Torque to front!

and that's cause for silly celebration

[Child's Play]

Man, this sounds sweet. I'm in the same boat as VehiGaz. If I could just have 4-High constantly at the turn on a knob or push button, that would be enough for me. Anyway, I'm completely lost in the post, but I did see this on E-Bay and thought it may help you guys out. Thought I would try to help out in some way, since I don't have clue one about what you guys are talking about. Here's the link:

http://cgi.ebay.com/ebaymotors/2000-...QQcmdZViewItem