"Lifetime" Transmission Fluid Change Dilemma (1 Viewer)

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I purchased a 2005 GX470 a while back with 165k miles. Currently it's sitting at 170k miles and the transmission has mostly felt fine except for cruise control erratically shifting on hills occasionally.

I know these transmissions come with "lifetime fluid" in the sealed units and I assume the fluid has never been changed since the previous owner did all maintenance at a dealership and I see no record of it being done.

Looking around, it seems like there's a belief that if the transmission fluid hasn't been changed for a long time (100k+ miles), then it should NOT be changed since the sludge in it actually helps with not slipping.

Another camp is that no fluid is lifetime and should be changed.

What should I do in this situation? Take the chance on the fluid change or keep driving around with original fluids and wait for the transmission to break?
 
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I think the advice to not change high-mileage fluid may be an old wives tale. Perhaps the reason it may have caused issues for some folks is if the fluid was changed by simply draining the pan through the drain plug and adding new fluid through the dipstick (thereby stirring up sediment in the pan and sending it back through the transmission), rather than doing a full flush where the pan is removed and cleaned.

I changed my fluid at 135K and it was dark but not totally cooked. The right way to do it is a full flush where the pan is dropped, sediment is cleaned out, the filter is cleaned or replaced (I just replaced it because the pan gasket set came with a filter), and all of the old fluid is flushed out and replenished from the transmission cooler behind the grille. This will get 99% of the old fluid out and get the sediment out before any new fluid goes in. I used Valvoline Maxlife ATF (half the cost of Toyota WS fluid and listed as an equivalent) and it's been fine since, but really not shifting noticeably better than it was before I changed it. There was a nice layer of sediment on the bottom of my pan, but not excessively so.

FWIW, I also changed the fluid in a GM4T65-E transaxle (no where near as bulletproof as the Aisin A750F the GX has) at somewhere around 150-170K in this manner. That transmission shifted SO much better with new fluid, it was like a new car. It was still going strong when I sold it at ~210K on the original transmission.
 
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Keep the principle in mind. Tires are designed to last a lifetime... their lifetime. So "lifetime" fluids are based on the "I drive XX miles a year, and this car will last XX years before I trade it in" thought process
 
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I would get it serviced even if they will just drain it and fill it. Do it every six months to rid of all the old fluid and prolong the life of your transmission.
Lifetime is good until the warranty rans out then it's all on you. ;)
Thats not the best idea. The pan only holds ~4 quarts and the transmission holds ~15 total, so it would take at least 4 changes to get it. And the new fluid would still be contaminated with some of the old. The flush from the cooler is the right way and gets all of the old fluid out plus pan sediment.
 
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It doesn't matter which is a better idea, bottom line is prolonging the life of the transmission. Being a 2005 and only got 170k previous owners probably use it around town or short trips which is not really good for any transmission. I worked for Lexus for a bit before getting into fleet and they did not do any flush they drain and fill it unless there is some problems that the customer would like to diagnose. I worked for Chrysler for 21 years and transmission issues are top of the list problems since the 90's and when they started coming out with vehicles after 2010 with " Lifetime fluid" we all had a good laugh. :rofl:
 
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IMO: After doing 4 drain and fills a few years back on my 460… no regrets it doesn’t have a dipstick, Overfill a little bit..no biggie…get up to check temp and drain it off via the check tube.

Not a AT dipstick fan after experiencing these easy changes.
 
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I just posted a write up on the drain and fill procedure. It really is not that bad to do. It took me a few hours one evening after work and it was good to go.
 

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