Transfer Case Lock Health Check

[Skyhawk13205]

I have been trying to find a simple way to determine if the transfer case locks. The only ways I can figure is to:

1: get it stuck and see if front and rear spin at the same rate.
2: check the c7 clutch pressure vs main.
3: check for binding on turns on a hard surface.

The safest and least damaging method I can think of is to just check the clutch pressures, but that involves some work.

My gripe is that the C7 clutch pack pressure is not monitored, there is no failure indication besides getting stuck and noticing the tires are not spinning. Any other clutch failures would give ratio errors or some type of feedback. It would be good to have some test or tryout to know of the failure before attempting to drive through an obstacle. I was thinking installing a pressure switch that would annunciate a light if the clutch pack is pressurized would be a great upgrade.

 

[Ronmar]

Well C7 pressure still isn't a "health check" it just means it is trying to send pressure... You could also look at the diff-lock indicator signal, which it alters when the difflock is commanded by the transmission via the mode indicator signal. These trucks use that signal(trans wire 125) to drive a VIM relay(SF04) in WTEC2 trucks or relay K34(differential lock relay), in the power panel on WTEC3+ trucks. that relay in turn controls the center axle power divider air solenoid.

When I did my standalone 4X4 switch I thought of using wire 125 to indicate diff lock, but the allison programming is reversed logic. IE: it is active/completing a circuit all the time and goes inactive/open circuit when the center difflock is commanded. So SF04/K34 is energized all the time and de-energizes when difflock is engaged, and it uses it's de-energized contacts(pin 30-87A) to complete a circuit to power the power divider air solenoid to get to 6X I guess I could use 125 to drive an AWD light that would go out when 4X4 is selected