Transfer case experts need your help. Chain noise in 2wd.

Rizzo1 · March 15, 2017

Hey guys. I'm hoping someone on here has had this problem or might know what it is. I have a 2009 Yukon XL with a 5.3 4x4. It has the 2wd / auto 4x4 / 4wd dial. When I drive in 2 wd the chain case will start making a noise and it sounds exactly like the chain coming loose and rubbing the side of the transfer case. It take a while to start making the noise though. Sometimes it will go 100's of miles before it starts. Then when I put it in 4x4 the noise instantly goes away and its fine. I can drive around in 4x4 for a while and put it back to 2wd and its good again for a while. The last time it did it I tried putting it in auto 4wd and the noise went away instantly again and it has not come back at all so in auto 4wd it must somehow keep the chain tight. I was going to just order a transfer case and a mechanic told me to check the switch and try replacing that first? He said sometimes the switches dont work properly and will allow the transfer case to slowly allow whatever it is in the transfer case to loose up the chain? I didn't think this was possible but you never know..LOL.. So just wondering if anybody on here has ever heard of this or has some ideas? Ive searched everywhere online and cant find any problems like this one. Lots of loose chains but they make the noise all the time. Ive been driving all winter in auto 4wd and its been perfect but I know as soon as I go to 2 wd the chain will come loose again. Its just a matter of time before it grenades so I want to figure it out. Oh. The truck has 142000 miles on it. I do all my own maintenance. All fluids are topped up and I changed all the fluids in the driveline last year and checked for any metal shavings etc in the transfer case fluid. Nothing. All the fluids were perfect.

Thanks everyone.