Auto Box Fluid Change

[is200 Newbie]

I cant see on the service schedule that the gearbox fluid ever gets changed - there is a note to check for signs of transmission leakage along with an inspection of the rear diff fluid at 80k miles

Are there any benefits in changing the auto box fluid - car is coming up to 90k and a lot of short miles are done so the box does work hard and I am thinking it would benefit from an oil change.

I have looked through the forum for anyone that's done this but cant find any mention - has anyone actually done it? Any pictures available as to where the drain plug is located (if it has one?) and how easy it would it be to do this or is it recommended to have Lexus or a good garage do it?

Also, does the box have a filter installed inside its pan?

[ChumpusRex]

You can't easily drain the fluid, as only a small amount of fluid sits in the pan. You would need to take the oil pan off, and even that won't get much fluid out.

The other issue is refilling it. Refilling it requires a special tool as there is no filling port.

[BillNick]

On that basis I wouldn't bother if it was me.

Diff oil is still every 20k though is that right on the auto??

[johnatg]

I think diff oil is 25K intervals (that's what I do anyway) - same on auto. It's not an interval you need to be too precious about.

Re the auto transmission fluid - the refill hole is behind a cover on the left hand side of the box - the cover is secured by two bolts. You do need something which will pump the oil horizontally, but then you need that for the diff oil too.There are two plugs in the oil pan - the drain plug is the rearmost one, the other is an overflow plug and is used to check that the level is correct.

There is a bit of a complicated rigmarole for checking the level and on the whole it's probably best not to mess. But having said that auto transmissions do benefit from a fluid refresh after 100K miles or so or if the change becomes jerky. Note that you can only drain 1.5 litres (out of 7.2 litres total) by removing the drain plug, so doing a significant refresh involves quite a few bites at the cherry!

There is a strainer between the oil pan and the valve body (ie above the oil pan). But I wouldn't go beyond the drain/refill of 1.5 litres unless there's a definite fault.

[is200 Newbie]

Cheers guys

I think I will leave well alone - I have read a bit about it now that confirms what you have said John ... a lot of confusion in the states as they consider this to be a sealer unit with no need to change the oil as..!?

When I do decide to get it done (if I still have the car then) it will be a dealer job I think. I can feel the gear changes when in auto and I don't think its as smooth as it was when I first got it but I cant really be sure. I was thinking that a gearbox oil change would improve it.

If the diff is at around a 20k interval then that will be coming up next year.

[jackcramerr]

What millage does manual state for gear oil change and differential oil change in UK/Europe where conditions are different.

[ChumpusRex]

Cheers guys

I think I will leave well alone - I have read a bit about it now that confirms what you have said John ... a lot of confusion in the states as they consider this to be a sealer unit with no need to change the oil as..!?

The unit isn't sealed, but there is no dipstick to check the level, and there is quite a palava to check the level and you are supposed to use a special tool to do the check and fill.

The unit uses a very special fully synthetic fluid which is designed not to degrade under normal use. Under extreme stress (towing), the fluid can break down and the friction characteristics can change. The ECU monitors this, and when it detects fluid degradation it will trigger the engine management light/check VSC with a diagnostic code for transmission fluid degradation, which indicates that the fluid should be changed.

[is200 Newbie]

aaahhh

I had a fault light a couple of months ago - LED me to the gearbox and when I checked it out it was one of those spurious codes that comes and goes with no real consequence - gearbox condensation on a sensor was what I remember reading reported a couple of times in the USA??!! Possible first indication of an oil change needed but has not come back since clearing.

Will keep an eye out.