Service 4WD and driveshaft vibration solved!
Hey fellow WK owners!
I've been dealing with a horrible vibration at about 73-78mph since I bought it with 56k on it and the occasional "Service 4WD System" intermittently until recently when it just stayed on. I finally got sick of it and decided to fix it now that my wife has to drive 40miles a day for work.
First, the drive shaft vibration. I kicked back on whether or not to go new shaft, junkyard, or try the Dorman CV joint repair kit (P/N# 932-303). I went with the Dorman kit. I thought it would be a cinch after looking at the directions, however for the life of me the bolts on the axle side of the drive shaft WOULD NOT COME OFF!!! So I ended up changing it on the vehicle. Not ideal but was able to be done, now if I had a lift and working air tools I would have taken it off. It took me about 1.5hrs. Bolted it back up and took it for a ride and i'd say 90% of the vibration is gone. What's left could be eliminated with new tires or a balance, a little hummm from the drive train but I feel better now.
Now onto the Service 4WD. The only way to find out for sure what triggering the light is with a comprehensive diagnostic tool. The cheap Advance/AutoZone ones only read emissions codes. These are "C" codes stored in the FDCM module. Any Genisys/Snap-On/Autel unit should be able to read that sub system. In my case it was a C1417 pointing to the front Diff. Next step was to unplug the pigtail on the top of the diff and use a multi-meter and make sure it was getting a signal to activated it. You can do this by engaging 4WD low on and off. You should see a voltage fluxuation. Next check across the poles of the solenoid side and check for resistance, should get about 14ohms. You can cross check the rear to make sure your doing it right. I was showing nothing up front.
Got the new solenoid. Drained the front diff and tool the cover off. Total PITA! The top three bolt were not pleasent. Lots of swearing and long extenions and swivels and I got it off. After 20k plus miles of a vibrating driveshaft I was not sure what I would find. The gear looked great, makes me even more sure I need new tires. The solenoid takes a minute to change, put the new one in, cycled the key and voila, message gone! Put a new line of gaskets material on, bolted and filled it back up, took it for a ride and everything is good!
I also put new front brakes on, but that had no effect on anything. I hope this helps someone else out there. As for the Dorman part it has a lifetime warranty so even if I have to do it again at 100k I'm ok with that.