As most of you all know I had my trans swapped not too long ago. Well, I know I had some issues with my transfer case not always engaging (even before the trans swap). I took my boat down to a local fishing spot and ended up getting my truck stuck. I engaged the 4 Low and I could hear the transfer case lock in and the drivetrain got stiffer but when I went to give it gas the front tires had absolutely NO power, my back tires just spun out. When I took it back to the place that did the trans swap they said they had noticed it wasn't working properly and the mechanic said he thought the vacuum line had pulled trans fluid up into the diaphram in the vacuum canister (under the battery). I have NO clue about 4x4 systems. Does this sound right? How much does this part cost and can I replace it myself???

 

If you notice a difference between 4HI and 4LO in your butt dyno, but are only getting rear tire slip, its a possibility that your front diff is not engaging.

Your mechanic's assumptions may be correct. Those vacuum diaphram's tend to rot out after awhile and no longer engage your front diff.

Not too hard from what I have read on here about pulling it out and inspecting it. Good luck, and let us know what happens.

 

X2 on the diaphram it is located under the battery tray and it dry rots pulle the batter tray and take a look