09 Subaru Impreza wagon centre diff ratio
When you turn slowly you feel like you get a
kick in the backside
You maybe experiencing a problem with the transfer cases internal clutch system. I would get it checked cases waiting too long can get expensive really fast.
There's no way to "check" the transfer case. What happens is that the Teflon coatings on the bearing seats are worn off. Try adding a small bottle/tube of TransX Posi-Lock (or similar name) gear additive after changing the old ATF from the tranny. Within a couple of figure eights you might notice the "crabbing" go away. If it doesn't within a day or two you may have ruined the transfer case. Some cheap wrenches use a shot glass of brake fluid instead, but better to use the Posi-D additive. Works wonders...but do start with clean ATF, as even dirty ATF can cause the problem. If yours is a STICK then the problem is invariably a worn-out center diff called a "viscous link", that freezes up instead of loosening when turning. It's a single $500 or so "pumpkin" that's pretty easy to swap in behind the manual trans. Good luck. Ern