Originally Posted by ALISC400

It is a liability issue for them. Let me provide you with a scenario. Another friend bought a '12 LS460. Brilliant condition yet it has a transmission/oil leak. This was because the seller literally did not bother to service the car AT ALL. They just gave it to the agency/dealership and thought that would be fine. Around 81,000 miles (131,000km) when the car was bought - he had to service the car anyways. Here (in UAE/Dubai) you would get a warning during your passing stage as this is a risk so this was classified as "passed" with a warning that if this leak is not fixed then this car would not pass again. Fast forward a few days, car ends up in the garage - fluids changed, gaskets replaced and everything is fine until 2 weeks later where the transmission felt sluggish. Now, filter and fluid was changed (Fluid was drained and replaced with new fluid) however with the fluid change... the gear started making a noise. A grind-y noise where you'd feel the gears either sticking and/or not shifting as they should. That smooth change was lost. Back to the garage. Now the mechanic says when we changed the fluid, we noticed metal fragments on the bottom of the pan. You can imagine the shock and horror to the new owner who basically is in tears.

Solution? Either open the transmission OR change the transmission entirely. I opted for the 2nd route as I know opening the existing one is just going to cause a headache. THE REASON why people should not change the fluid is it actually is keeping whatever is inside together evenv if its breaking apart HOWEVER this also is a reason to really take care of this and not go on the notion where your transmission fluid will "last forever". Now what I did for both my cars was drain the existing fluid and top it up with new fluid. I've not changed the oil to some other brand or tried something radical (posted below)

Again this will be a long post but for my LS430 and my SC400, I changed the fluid and I felt a better shift and a minimal better drive at the end. My SC feels way stronger at the gears/revs/pull than my LS does? I push the car a lot but the LS does shift a bit quicker and smoother now that I changed the transmission fluid. I know some people may have different stories but I do feel you'd need to change it at some point. Just a reminder that here within the Gulf, a lot of older Lexus models are imported. They ususally sit there for ages until someone comes and buys them off a lot or off an auction house floor so you really have no idea of the general maintenance. The newer-ish models which are GCC spec (bought and sold here within the Gulf market) again are a risk cause most do not care about leaks or general maintenance of these cars especially when it is the higher end models such as the LS. So far my LS and SC have not needed a transmission change or anything like that but I have replaced the fluids but I know why people would stay away from that as you'd find out bigger issues if you did go forth.

Originally Posted by rick3242

It is my understanding that the main issue with transmissions after fluid change is how the fluid was changed. If it was flushed then the flushing process will stir the debris / shavings and end up clogging the veins of the transmission and torque converter. However, if the fluid is drained and refilled their is no high pressure that will stir the debris / shavings and the chance of clogging veins is much less. Ask me how I know and I will tell you about my 2010 tundra flush and two drain refills later. So if you change your fluid ensure that they drain and refill only. This will introduce new oil in your system without the harmful side effects of flushing. I plan on draining and refilling my transmission at 100K miles.

Originally Posted by ALISC400

Well the friends LS460, fluid was drained - no pressure added. No flush, a simple drain to replace the old fluid however a few metal fragments were in the oil/fluid pan after they drained it all out. I believe if you already are heading to failure then this will be a problem. His issue was the previous owner who must have driving this to the wall yet he did want to flush previously and that would have been a bad idea. His transmission was on its way out but the fluid change just sped that up.

I would not recommend a transmission flush at all.

Originally Posted by Thegamemhb

I my self think that flushing engine or trans can create bigger problems i am just thinking to top the oil or drain n refill without flushing it .. i had a good experience when i changed the trans oil of my 2009 land cruiser the trans was smooth it did shed some shavings but dint create any problems for me