Originally Posted by bobeeker
Ok I checked all hoses and no leaks. I checked the vacuum solenoids and they are working as well. I cant tell though if they are fully working or not as I dont know how to test them other than felling the vacuum.
That's about the best way. If you had a vacuum gauge, you should see both sides being equal, and I'm sure there's a spec, but it shouldn't take much to actuate the Center Axle Disconnect. I assume you checked for vacuum at the actuator too? Also, you should not have had vacuum on BOTH solenoids at the same time, correct?
Is there anything else that it could be.
That leaves either a problem with the CAD itself, of the differential guts, and neither one is a cheap or simple fix. I've never played with the actuator manually, but I've been told that you can pull the boot back and inspect the shaft where it slides in and out of the actuator. JMC is a bit more familiar with those guts than I am, so it would be worth an e-mail to ask. Tell that Canuck I sent you, but make sure you type slowly and use small words LOL!
What are the solenoids actually pulling in. Is it possible that what ever they are pulling in is not going in fully.
The vacuum actuates the center-axle disconnect on the front axle. Basically, in 2wd, it breaks the passenger side axle shaft between the diff and the halfshaft. That allows the differential carrier and front driveshaft to stop turning when in 2wd. The spider gears in the front diff are still driven by the driver's side halfshaft, but as long as the fluid level is good, they don't pose much of a drag on the system. But I digress...
The center-axle disconnect has a vacuum diaphragm and actuator that slides a collar over the two halves of the axle shaft. I suspect that either the actuator is sticking (in which case it probably wouldn't engage in the first place) or it may not be fully engaging (they sometimes get rusty or gummy and only engage part-way). It's also possible that the fork itself is bent or broken, or the nylon feet that engage the collar have worn enough to allow the gear to disengage under extreme loads. Without taking it apart, I have no idea.
I am leaving for the coast in like 3 weeks for 2 weeks and still dont have a 4 wheel drive truck. What would be your next move if it was you. Thanks again for all your help.
I would do one of two things: Take it to a good driveline shop and have them drop the front axle to see what's going on, or hope a dealership doesn't rake me over the coals on the diagnosis and repair. The only other option would be to disassemble the CAD (If it can be done without dropping the axle... I don't know offhand). If you're dropping the axle, I'd pop the cover and see what you can see in the front axle too. It's possible a chipped spider gear could cause the problem... if it gets to one particular gear alignment and pops out, that could do it, I suppose, but there's no way to know without removing the cover.
(My million dollar idea: a portable auto X-ray/fluoroscope. You'd be amazed at what you can see without opening up a part! We have one at work and the info you can get is truly amazing!