Good find with the lines!
I have seen some TCCM's do some funky things with the IWE's, but I find it interesting that yours grind once engaged. But that being said
@Idaboy did what I've had to do on a few vehicles, and change the hubs as well. I've seen the IWE teeth wear the hubs out as well. But that's usually on the 4A trucks, which you said you don't have. But it could happen if for some reason the truck is losing its vacuum intermittently while driving and causing those teeth to engage and disengage over and over again.
With the vacuum issue though, I find it odd that 2 solenoids would be shot. So if you're feeling up to it you could do a couple of things to steer you in the right direction.
- First I would check that fuse 39 in the BJB is good. It's a 10A. Either visually, or stick a test light in pin 1 (SBB39 WH-RD) of the solenoid connector to ground and see if it lights up. If it doesn't you could have a blown fuse or high resistance in that circuit.
- Jump the solenoid manually to battery voltage and check for vacuum on the exhaust port (upper port) of the solenoid. If there is vacuum, and if your power circuit has been verified to be good (first step) then you need to check the integrity of the control circuit (wire to tccm)
- If you know how to do it, I would then perform a voltage drop test on the control circuit (CCF05 BN-BU) from the solenoid to the TCCM. It's possible the connector pins or the splice inline (S100) may have high resistance.
- If all that is good, then you may be looking at a TCCM issue, or switch problem.
Hope this helps at all lol
Here's a picture of the circuitry.