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@Xengineguy Ok, i got a chance to take some readings. I don't have a 3 Ohm injector or solenoid to measure into so these were taken into a 85 Ohm 12v relay coil. Readings taken with a Fluke 87. My A0 WTEC2 TCU won’t enable diff lock until the engine is running. with the ignition on I get...

Ok, MY 4WD problem is solved. It was my VIM delete. A friend of mine shared some info about an issue he heard of where the 4WD failure turned out to be a bad 161-163 circuit. This pointed me back toward the VIM as that circuit does go thru the VIM. I misidentified that circuit when I did my...

Low impedance and peak/hold PWM to vary the current allowed more rapid and precise control. it makes sense to have just one control scheme and stick with it, even though the C7 solenoid really only needs to be an on/off. In the 3060 troubleshooting manual it states that the H solenoid(3060...

You would need to limit current flow with direct DC otherwise you would cook the low impedance C7 solenoid coil. i am not sure if the C7 solenoid valve vents when open, but I was able to feed air into the clutch port and engage it, with little apparent leak-down, and the air I shot in blew...

I checked the diff-lock light/power divider signal(wire 125) and it is also not changing state with mode either, but the trans display indicates mode and shifts to the 5 speed limit… this is starting to look like TCU output for my issue, grumble grumble. I will pull the TCU out and see if I can...

Ok after checking today i see no signal change of state when selecting or de-selecting mode so I am going to have to look into this further. What I do see is 7.4Khz pulsed at a 29% duty cycle whenever the ignition is turned on. Allison uses a 2 stage peak and hold Pulse Width Modulation...

You know I have looked at that diagram in appendix B of the troubleshooting manual about a hundred times over the years and never managed to pull that 7/16-20 note out of it:) thats exactly what I needed, thanks… 1/4” or -4 ORB, same as what is on our hydraulic cylinders. Have plenty of...

There is no debris in the case or strainer, drained it this summer confirming speed sensor source and tooth count. Dont think they are a failsafe config, i guess I will be finding out. I did notice the controller output for the diff-lock light(wire 125), that we use to control the power...

Dont have them on yet. It has had to wait untill i could get my cab suspension fabricated. The C7 pressure isnt monitored, which is why I will need to hook up a pressure gauge. The solenoid electrical circuit is Monitored, Which is how I know it has a good circuit, because it sets a 45-23...

Did you ever resolve this? Was backing up in the snow into my garage today and discovered I only had the 70/30AWD split in mode… the TCU is monitoring a good circuit thru the solenoid(threw a code when I disconnected it), so either the TCU isnt sending the signal, or the valve is not opening...

This could be as simple as that C7 valve down in the transfer not opening fully. If it were something else leaking I would expect to see a significant drop on main pressure, but if it was driving thru gears fine in mode it does not sound like that was the case...

Also which main did you check? I suspect they used the retarder control circuit(solenoid H) to control center diff lock(note in the schematic shows H and output speed sensor either going to retarder or transfer case). Main pressure is fed aft into the transfer case housing and down. There is...

Was that with C7 engaged? My reason for asking was if you had something gushing i would expect to see a drop in main pressure. I am sure it is normal for all the clutches to leak to some extent and the pump makes up for that with enough volume To maintain adequate pressure. But if there was...

probably the slower speed of 1st allowed enough torque to pass the friction material so it appeared to be working in first… did you by chance check main pressure?

Well thats weird. I suspect if it were a pressure issue it would have issue engaging in 1st and mode, but since it engages in 1st and NOT in mode, this almost sounds like a programming issue… your gear range drops to 5 when you select mode right?

Hmmm. Engages in 1st, but not in mode... thats weird as the signal comes from the same place. first off, how are you determining that it is locked or not? The center dif valve is in the transfer. The signal for it as well as output speed sensor run thru a cannon plug on the front side of...