Automatic Transmission and Differential Fluid

I own a 2005 Tacoma with 160,000 miles. I bought it from a guy with 149,000 miles on it about a year ago and can tell that automatic transmission fluid and differential haven't been changed in a while because the previous owner did not seem like the type of person to do maintenance. I've been told by my friends who are mechanics to not worry about it and dont bothering changing it at this point and that it will be fine, but I just wanted some other opinions to see if i should at least change the differential fluid.

 

Yes you definitely should change the diff oil. I question their validity if they say otherwise. It's cheap and easy. The transmission, I don't know. They can be fickle bitches but I would do it.

 

2wd or 4wd? Personally, I would change the diff fluid if I were you. If it is 4wd, I'd opt to change the front, rear diffs and transfer case fluids (redline 75-90 on all 3). I would also do a partial service on the trans (toyota fluid) - ie drain and fill.

 

Regardles of the type of person the previous owner seemed to be... either you have maintenance records for the truck, or you do not. Your maintenance decisions should be based on that information.

 

I would definitely change the diffs... As for the trans??? I have read 100's of opinions. There is the myth that the flushing machine dislodges dirt and plugs everything up... I would be tempted to drop the fluid that is in the pan and replace it with new. Let it ride for a few weeks and do it again. Do that three or four times then drop the pan and clean the screen. Hopefully we can summons the mighty @gearcruncher and get his opinions. He is one of the few that have actually been inside the belly of the beast. If you swap it slowly then you won't shock the system. There is very little love on here for Toyota WS fluid. I'm not sure, but a 2005 may not need the WS and you might even have a dipstick. If not you will have to find the threads on how to check the fluid at the magic temperature. It's not easy but it ain't rocket science either. If not going back with OEM WS fluid then valvoline Maxlife with the WS rating seems to be the universal favorite on here. If 4x4, then do the transfer case too. I have changed my power steering fluid as well and I am @55k miles. Also flush and change the cooling system. Brake fluid is another good thing to change as it absorbs water over time. Good luck!!! It has become a real pain in the ass to use the search bar on the forum, but all this is trapped in the threads somewhere LOL. Also when you are done with the trans I have really come to believe the hype of Lube Guard. Finally I would be thinking about some new spark plugs at some point.