Me and others have commented before about ADD issues which can be read about here and here. Well this story is a little bit different, but in the end same results - I needed to replace the ADD actuator unit.
I went on a 3-day backcountry trip a little while ago. Had no issues during the entire weekend and got off the trail Sunday and we drove into town to gas up. We used the local coin-op car wash to spray off the excess mud in the wheels and stuck to the bottom of my truck. Got back on the highway and about 15 minutes down the road my VSC OFF dash light comes on. I've had this occur before and thought, oh, it's just a wheel sensor harness that got wet during the power-wash and will dry out in day or so. And typically it does dry out and the light goes away after a day or so.
Couple days go by and I start thinking something else might be wrong, especially because now the 4WD light starts flashing after driving for exactly 30 minutes from the time I start the engine. I took it to friend's garage and they pulled all sorts of codes that indicated all the wheel sensors and the ABS ECU. *Slight Panic*
Another friend had a wireless OBD-II scanner that we could reset the codes and then drive around and watch the codes pop up. He could select which metrics to monitor and selected the wheel sensors, the actual speedo sensor, the ABS and 4WD ECUs. He could manually turn the VSC OFF light on and off with the scanner tool so that verified it wasn't a freak bulb or wiring issue to the dash indicator. The wheel sensors matched the actual speedo, sigh of relief. We shifted to 4Hi and 4Lo and back to 2Hi. So the scanner had suggested that it was something between the front axle sensor (ADD) and the ABS ECU (but not the 4WD ECU), possibly a ground /fault in the wiring harness. We checked the ABS fuses and wiring harness and everything looked good. At that point I felt pretty confident that it was the ADD unit. We crawled underneath (now that my skids were removed) and looked at the unit. First thing we notice is that the breather tube was disconnected. The port on the side of the ADD was open to anything. Ohhhh, that was a bad sign.
I pulled the ADD off and opened the housing this past weekend and thought I'd find a little sediment or something that I could clean out of the worm gear or something easy. First thing I notice when I pulled it off was that the shift collar was in the ON position meaning that the passenger side half-shaft was engaged with the diff. Not a huge deal to the running gear, but would explain why the truck thought it was in 4WD (VSC OFF light positive), but didn't act like it. And when I shifted it to 4Hi, it might have been disengaging the shift collar? Dunno yet. I'm guessing the flashing 4WD light comes on after 30 minutes of the ABS and 4WD ECU's trying to sort out what's happening.
Here's what I found inside the ADD housing - muddy water, motor corroded and the micro-switch (detects engagement) is probably not working. Called Sam Stewart right away and have a new one arriving this week. For now the old one is cleaned up and back on the front axle housing. I will get the new one on this weekend and update with any progress.
I went on a 3-day backcountry trip a little while ago. Had no issues during the entire weekend and got off the trail Sunday and we drove into town to gas up. We used the local coin-op car wash to spray off the excess mud in the wheels and stuck to the bottom of my truck. Got back on the highway and about 15 minutes down the road my VSC OFF dash light comes on. I've had this occur before and thought, oh, it's just a wheel sensor harness that got wet during the power-wash and will dry out in day or so. And typically it does dry out and the light goes away after a day or so.
Couple days go by and I start thinking something else might be wrong, especially because now the 4WD light starts flashing after driving for exactly 30 minutes from the time I start the engine. I took it to friend's garage and they pulled all sorts of codes that indicated all the wheel sensors and the ABS ECU. *Slight Panic*
Another friend had a wireless OBD-II scanner that we could reset the codes and then drive around and watch the codes pop up. He could select which metrics to monitor and selected the wheel sensors, the actual speedo sensor, the ABS and 4WD ECUs. He could manually turn the VSC OFF light on and off with the scanner tool so that verified it wasn't a freak bulb or wiring issue to the dash indicator. The wheel sensors matched the actual speedo, sigh of relief. We shifted to 4Hi and 4Lo and back to 2Hi. So the scanner had suggested that it was something between the front axle sensor (ADD) and the ABS ECU (but not the 4WD ECU), possibly a ground /fault in the wiring harness. We checked the ABS fuses and wiring harness and everything looked good. At that point I felt pretty confident that it was the ADD unit. We crawled underneath (now that my skids were removed) and looked at the unit. First thing we notice is that the breather tube was disconnected. The port on the side of the ADD was open to anything. Ohhhh, that was a bad sign.
I pulled the ADD off and opened the housing this past weekend and thought I'd find a little sediment or something that I could clean out of the worm gear or something easy. First thing I notice when I pulled it off was that the shift collar was in the ON position meaning that the passenger side half-shaft was engaged with the diff. Not a huge deal to the running gear, but would explain why the truck thought it was in 4WD (VSC OFF light positive), but didn't act like it. And when I shifted it to 4Hi, it might have been disengaging the shift collar? Dunno yet. I'm guessing the flashing 4WD light comes on after 30 minutes of the ABS and 4WD ECU's trying to sort out what's happening.
Here's what I found inside the ADD housing - muddy water, motor corroded and the micro-switch (detects engagement) is probably not working. Called Sam Stewart right away and have a new one arriving this week. For now the old one is cleaned up and back on the front axle housing. I will get the new one on this weekend and update with any progress.
