If the noise goes away when you select 4WD, its most likely the vacuum switch on the transfer case.

 

The noise just started and stopped on it's own I never touched the 4X4 dash switch at all and I was in 2HI. I haven't used my 4X4 in about a week I pulled the 4X4 fuse so if it does happen again I guess it'll have to be a bad switch motor on the T-case

Thank you again for your reply
Happy Holidays

 

Classic symptom of a leaking vacuum switch so removing the fuse will have no affect.

 

Ok thank you very much Captain is there an easy way to test this? i was just thinking of removing the vacuum line from the actuator and having some one hit the 4HI button and seeing if i get vacuum and have them hit 2HI again and see if i still have vacuum, Buy the way it just happend again in the exact same spot as yesturday, I forgot to mention in my first post that I was going up hill when it happend and I was on that same hill tonight, while cruising at 80 Km up the hill the transmission down shifts and a bit later thats when I notice the wineing noise of the front diff and again once I slowed down to turn off at the same spot the night before onto the side street, once I got down to about 40km there is a slit jurk and it's gone away agian I forgot to mention that in my first post as well.


Would this still be the vacuum switch? Why would it only happen when I'm at an incline? this is really weird

sorry for the long winded post but just wanted to get all the info down


Thanks everyone for any and all help you can give

 

If you pull the vacuum line off the actuator under the battery, with the engine at idle: in 2WD there should be zero vacuum. In 4WD there should be manifold vacuum. The fact that yours is intermittent, it would be best to put a vacuum Tee in the vacuum line to the actuator, then extend the vacuum line into the interior of the vehicle and connect a vacuum gauge to the line. Be careful not to kink or pinch the line. Doing it this way you can operate the vehicle and monitor the vacuum that is being applied to the actuator while you're driving. In 2WD there should be zero vacuum at all times. When you select 4WD there should be manifold vacuum at all times, (approximately 18" Hg). When you shift back to 2WD, vacuum should drop to zero immediately.

The vacuum switch on the transfer case,



has a spring loaded ball that is operated by linkage inside the transfer case when shifting between 2WD HI and 4WD HI, (called a "mode shift"). Normally these switches get stuck partially between 2WD & 4WD which allows a slight amount of vacuum to leak past the seal in the switch. When this happens, the actuator slowly starts to engage the clutch on the right front axle, that's when you hear the grinding noise. Depending on what position the switch is stuck in, the axle clutch might be "mostly" engaged all the time. If that's the case, when going uphill, manifold vacuum decreases and the clutch could partially disenge causing the noise. Check it out and post your results.

 

Thanks again Captain for the advice, but I think I'm just going to replace the vacuum switch it's only $17 on rockauto.com, I'm ordering new Delphi O2 Sensors from them anyway so it's no big deal adding another part, so once I replace it I'll post back if it's fixed or not

Thank you for all the help