I would definitely recommend changing it via an exchange (not flush) if you plan to keep your 4Runner. There are how-to threads available; be sure you understand the process whether DIY'ing it or discussing with a shop.

Without going down the rabbit hole of the big debate on this, a manufacturer's definition of "lifetime" is usually different from an owner's:

Manufacturer: while the warranty is in effect (typically 100K miles)
Owner: While I own the vehicle (no set mileage/time limit)

There's also a suggestion that manufacturers declare fluids as "lifetime" because that enables them to avoid paying an advance disposal fee imposed on imported vehicles under the assumption that non-"lifetime" fluid will have to be disposed of one day.

In any case, your fluid is now old enough to vote so @SurferUK really nailed the bottom line: "Fresh fluid good, old worn fluid bad!"

I concur. Get that old stuff out as per the drain-fill process noted above. There's nothing that old fluid can do for your tranny that new fluid can't do better.

You'll be disgusted when you see the color/condition of that old fluid.

Just bought a 2004 V8 with 181k miles and was thinking about swapping the ATF. Sounds like it might not be a bad idea.

Any tips on not breaking the pan bolts when trying to drop the pan?.
Am trying to drop the pan, 3 bolts broken already, what am i doing wrong???. I dropped it 4 yrs ago and didnt break a single bolt,
Somebody help

When you dropped the pan 4yrs ago did you clean the threads on the bolts and pan before you installed it? Also did you torque them properly? They only take something like 7ft.lbs IIRC. The two biggest factors for those little bastards breaking are corrosion and improper installation (if it's been done before).

In the case of the corrosion, I would see if you can find something specifically designed to eat the type of corrosion that forms between aluminum and steel. Though I'm not sure if there's anything out there that will be aggressive enough to dissolve/loosen the corrosion without damaging the pan or transmission case (if you find something that works, please link it for us!).

But in lieu of that soak the crap out of them in something like Seafoam Deep Creep and try just "cracking" them loose a quarter or so of a turn, soaking them, and then trying to turn them again. It's a tedious ***** to do it that way, but I have had some luck when I have had to deal with crusty cars...

Also the bolts themselves are M6x1.0 and are about 25~30mm long I believe? So in terms of drilling and tapping you should use a 5mm drill bit. If you don't have one, a 3/16" is slightly under and a 13/64" is slightly oversized, I'd start with the 3/16" and see how well it lets you thread the hole, if it's too tight go with the 13/64", last thing you want is to break a tap in it.

I'm not sure if heating up the aluminum portion of the case a bit to help "wick" in the penetrating oil will help in this case, it's such a large heat sink it probably won't be worth it.

so, i have realized my mistake. rookie error.,for some innane reason i wanted to crack the bolts first before draining the tranny fluid. after the last bolt broke,it just struck me that the weight of the fluid could be the cause of the bolt breakage i drained the fluid and all the bolts came out freely.

Learning Point: always drain the tranny before attempting to loosen the bolts.


for drilling out the broken bolt,the upper part of the tranny housing where the bolt sits is a closed end, its likely that i would hv to drill through this closed end while attempting to drill out the broken bolt. this shouldnt be a problem, i hope?

You made no mistake by not draining the fluid first other than the mess it would've caused trying to catch the fluid coming out by not draining via the drain plug, the bolts were either seized or over tightened to the point of about to break, or you turned them the wrong direction trying to remove them.

There's no way only 3 or so quarts of the fluid in the pan could weight enough to put undue strain on the bolts to cause them to break.

You don't want to drill the broken bolts any deeper than the length of the bolts or you could cause damage to the transmission, it's possible that you might not cause damage but it's best to err on the side of caution just to be sure, besides being there's no reason to drill them any deeper.