Differential fluid change

I just recently bought a 2009 4wd drive tundra with 155k miles on it, I asked the previous owner if the diff fluids were changed while he owned it and he said no so I was thinking it would be a good idea to give it a change. Does anyone have any insight on this? I own a 2002 Tacoma that's front diff went out due to no attention to changing the fluid, when I went to change the fluid it caused both the front and back diff's to leak. The front was fixed with a new seal but the back continued even with new seals. I would like to prevent this with my tundra I just got, any thoughts or has anyone change there fluid there selves?

 

Would you happen to know what kind of gear oil the tundras take?

 

I'm using Mobile 1 75w-90 LS. LS only means that it's OK to use in limited slip diffs. (Marketing thing) Some folks run with M-1 85w-140 in heavy towing situations.

 

Are both of those brands synthetic?

 

https://www.google.com/#q=is+mobil+1+gear+oil+synthetic

 

I use 85W-140 during the hot months and 80W-90 during the cold months. Conventional is cheaper so I use that since I frequently change the gear oil anyway.

 

I just completed this and posted a DIY here:
https://www.tundras.com/threads/diy-front-differential-and-transfer-case-fluid-instructions.10743/