It is pretty costly to do the tranny/diff fluids, cause the fluid is pretty expensive. I have been able to get them to do it for 120.00 at the dealership, with a coupon.
Robbie did it for me once and his price was very reasonable.
They recommend doing both the first time at 60k, then again at 120K and then not again until another 120k. I think.. It gets longer after the first 2 changes.
After 2008, FJCs and 4runners come stock with synthetic oil, should say that on the plug. Pretty much the same process I am guessing as your 40 for the rear diff. The fronts are kind harder, I think you have to remove the OEM skids.
If your runner is the off road version, I bet it has a breather up in the engine bay for the front diffs, so fording water is no big deal. After a few deep water crossings in the Delores, I changed my rear diff on my FJC, cause I had not done the rear diff breather yet. I thought for sure I had taken in water and when they changed it, it was perfect.
My point is just change the diff fluids when they recommend, regardless how much off road your doing. You also might want to do the rear diff breather, if the 2010s don't come with an elevated breather.
There is a great thread on how to do it in the FJC forum. I bet the same parts will work on your 2010, cause I think the FJC still shares the same rear diff with the 4runner.
Hope this helps.
Note: I just realized my comments are all on your diffs more than tranny stuff.
Last edited by Caribou Sandstorm; 10-13-2013 at 11:09 AM.