I want to change the rear diff fluid in my 2012 GS 6M and cannot find the drain plug for the diff. I have checked a number of how to sites that shoe the plug between the rear spring and cross member but I do not find it on mine. I am also changing the Trans fluid as well and would appreciate any recommendations for fluid to use in my 6 speed. The car has 37000 miles and is not tracked or used hard. Any input is appreciated.

 

Don't bother changing the dif fluid. There's a reason that the owner's manual doesn't list it on the maintenance schedule. Because it's good for 150K miles.

 

I swap mine every few oil changes. The drain is under the pumpkin, the fill is through the cooler lines. Its an E clip that holds the cooler line in place. If you decide to do it, get a replacement E clip since those have been known to break on removal. Look up Z06 differential fluid change since we share the cooler setup.

I personally use redline D4 atf in the trans and M1LS in the diff

 

Pretty sure those are 60K mile service items. Did mine then. Not too bad. My clip didn't break, but I had a spare just in case. Guess I was lucky. Any reason for wanting to change yours now?

 

At 37K, leave both the diff and trans fluids alone.

As for fluids when it comes time for the change (read around the 100K range), use the OEM fluid, and not an after market fluid.

The break down on the trans, is that it'ssynco's required the specified fluid for them to last the longest. Use a fluid that has too much slip, and the syncro's will not lock up as intended. Use a fluid that does not have enough slip, and the sycro's end up locking up too fast isntead. Both of these later conditions will cause the syncro's to wear out faster than normal.

On the diff, before you think fluid change, put a torque wrench on each axle nut set to 100lbs, and with just that tire up in the air/trans in gear as you check, axle should not start to slip/turn until you hit the 100lbs. Again, we are using the OE fluid since it has the correct percentage of slip modifiers, and if say you where using a fluid will too much slip, going to cause the diff clutch packs to slip before the 100lbs torque (read a lot of peg leg burn outs). Now at the 100K range of just street driving and the clutch packs are not holding to 100lbs of torque, then it's time to pull the diff apart to replace the worn cluck packs isntead (read do the fluid change when putting the diff back together).
Note, have seen the OEM diff clutch packs burn out in less than 20K with lot of road course work. So again, first check on the diff is the torque wrench to see the torque value of where the clutch packs are allowing release. If below 100lbs, then either wrong fluid being used (not the oem fluid), or clutch packs need to be replaced.