Well I am pretty sure I have a problem with the 4WD vacuum system on my truck. For a few months it has been giving a very noticable grinding noise when under load from 40-50 mph. At first I thought it was the cat shields, because mine are all bent up from putting in the hi-flows.

My 4WD still works, no doubt.

The other day when putting it in 4WD for the first time in months it took a few seconds to engage and even though I wanted to put it in 4-Low in went into high. Then when I went back to High it went to Low. Then when I tried to disengage it took a few switches on the **** to get it to unlock, then it worked fine.

Sounds like the solenoid to me, right?

 

I would check the vacuum lines first and if that's not it, then move on to the solenoid. It happen to my 06, I had a small hole on the passenger side down by the exhaust manifold.

 

Well, remember that when you turn your 4wd on, you remove vacuum from the IWEs. So, it is possible that you would have a slow leak which causes the IWEs to partially engage even though you have selected "2wd", but when you select "4wd", you remove vacuum, and the IWEs engage correctly.

If you have been noticing a grinding noise for some time now, I would be looking to change the hubs as well as the IWEs, and maybe even the front axles. Only partially engaging the IWEs can lead to some pretty significant damage to the teeth on the hubs and shafts... I agree, though, start with trying to isolate vacuum loss as that is the most inexpensive route. But if time is money, IWEs can be changed out pretty quickly, and you might not have to go hunting for a vacuum loss.

Good luck, man. Keep us posted.

 

How did you find the hole? I have a hole in mine and I can't find it

 

I have heard that you should not go long periods of time (months) without putting it in 4x4. Crap can build up on the non-moving parts and lockup bearings/CVs and such, and prevent 4x4 from engaging. I drive on gravel a lot during summer so at least once every 2 weeks i drive it in 4x4 a bit. If you can, find a dirt road or gravel road and throw it in 4x4 for a short period every month minimum. Not sure if this is related to your problem, but just good practice.

 

Is this issue common to both manual and electric transfer case?