Hello guys newby here , thanks to this thread I figured that my TC was damaged and Mazda replaced under warranty all good till yesterday , I took the family for a trip and drove 60 highway miles on my 2012 cx9 with 37k on it and new tc like I mentioned before then the parking place was kind of on an inclined so when attempted to park I can hear this awful sound like something grinding then felt like it locked in place and was ok , what else could be making that sound I forgot to mention that the tc was installed only a week ago.
sorry to hear about your troubles, only thing that I can think of that may cause the grinding sound is the splines from the transmission that connects to the new transfer case, you should bring the car to the dealer and explain the grinding noise and ask them to check the splines of the transfer case/transmission connection while it's still under warranty.
just a quick question: before you realized that your transfer case was toast, did you smell any burning oil or notice leaking black oil between the two front wheels ? that's usually the first symptoms that the transfer case is going bad and shouldn't be ignored. At this point, it is still possible to save the transfer case/transmission by swapping out the oil and getting the lubrication the TC needs before it burns itself out and seizes.
this is just my theory so take it with a grain of salt, seems like your original transfer case failure caused the transmission spline teeth to shear a little, not all of it, otherwise you wouldn't hear the grinding sound at all
see this link here :
http://www.mazdas247.com/forum/showthread.php?123831170-Transfer-case-SB-03-005-11&highlight=spline
what happened in the link above seems like a domino effect:
1) transfer case oil broke down and turned to sludge
2) due to lack of sufficient lubrication, the transfer case overheated beyond it's intended design
3) transfer case internal gears got so hot due to lack of oil that the gear metal fused and seized the transfer case gears
4) once the transfer case seized; a loud "pop" was heard, most likely the sound of the transmission splines shearing off since the transfer case wasn't turning
5) car can still run but now basically a 2WD instead of 4wd because transmission is now de-coupled from the transfer case
if you read thru the thread, the worse part is that we can't just buy the damaged spline part, have to buy a whole transmission or just live with 2WD which for most is not an option in winter snow/ice.
it is safe to deduce that the CX-9 transmission is sound, otherwise 2WD CX9 owners would also be chiming in about transmission failures left and right which isn't the case. so can conclude most of the problems are from the transfer case.
there's more than enough evidence on the internet that shows the TC oil turns into sludge, do a google image serach for "Ford Edge transfer case sludge" there are photos of the transfer case disassembled.
BTW, Ford Edge uses the same exact transfer case as the CX-9
I can't stress it enough, it is imperative to do oil maintenance, there is no such thing as lifetime oil.
for the CX-9 transfer case every 15,000 miles or less
AND also do the
transmission oil drain and fill every 30,000 miles
(dealers will try to upsell the transmission flush but drain and fill is the way to go)