Transmission service

Gdetrailer wrote:

OK.. I will bite..

Have you ever thought that the manufacturer would like to ENSURE they will get future sales?

Transmission oil DOES break down, but at a much slower rate than say engine oil..

Transmission oil is basically HYDRAULIC oil, only with a few "additive packages" blended in..

I can tell you this, with owning a tractor with a front loader and backhoe, hydraulic fluid CAN get worn out by contamination from the AIR.. More specifically MOISTURE in the air. Hydraulic fluids are "hygroscopic" , in other words it ATTRACTS MOISTURE..

Learned that the hard way one extremely brutal cold winter when my hydraulics FROZE.. Yeah, the water suspended in the fluid FROZE and plugged the filter..

So, in some respect, "refreshing" your transmission fluid IS A GOOD THING TO DO if you wish to have a transmission with a long, long life.

I will however disagree with folks that feel the need to change out the entire volume of fluid by using a pump exchange or needlessly changing fluid at 30K or less intervals.. I would however recommend reading your owners manual and use their figures for the mileage especially while under warranty.

Forced pumping risks damaging pump seals and many newer transmissions require a HEATED exchange (IE transmission has a thermostat that needs warm fluid in order to open the external cooler circuit).

Personally, I simply dump the fluid that is in the transmission pan (newer vehicles often have pan plug other wise you will need to remove the pan). Then refill the pan.

I have waited as long as 80K miles for the first time since most of my driving is highway miles which helps drive out any moisture that the fluid may have attracted.

Doing this several times over the life of your ownership of said vehicle will refresh the oil.

So far, this has worked well with my 2003 F250, has 200K miles on the transmission and still going!

You are right on all counts but I still stand by my words and let me tell you why. These new automatic transmissions are sealed for a reason. The sealing keeps out dirt, dust, grit, and to some extent the water you are talking about. The engineers have designed a transmission that if left alone, will last a certain lifespan. I don't know off hand however on the tundras like my 06, I expect 250,000 on an average truck. If you drain and refill the fluid, yes you are refreshing the additives and draining contaminants however you are also possibly admitting dust, dirt, grit, and moisture to the inside of the transmission. Yes, a tiny amount but still not what the transmission was sealed up with. The lifetime oil means for the life of the transmission which is has been very reliable across the Toyota product range, aside from some mid nineties Camrys.

On the contaminants, the transmission is designed to function correctly with those contaminants floating around in there. If you look at the filter, it is just a coarse mesh strainer now, designed to catch any big chunks. Much like plain engine bearings like con rod bearings, that are designed with a soft base metal like brass that will imbed big particles that aren't caught by the engine oil filter, the trans is designed to function perfectly with junk in the oil.

Toyota engineers figure the best lifespan of the transmission is to follow what is written in the owners manual because the engineers wrote it. It's there in writing forever and if it is there in writing, Toyota knows some lawyered up yuppie can and will come after them in the future if what is written in the owners manual is bad info.

In the end, you can feel free to second guess the engineers, the legal team, or Toyota as a company but understand you are probably not a mechanical engineer with a lot of schooling and experience to draw from.