Auto transmission fluid - drain and refill or complete change?

Looking to change the automatic transmission fluid on my 2005 Lexus RX300 and the Owner's Handbook lists the capacity as 3.5 litres for a drain and refill. I'm assuming that that figure doesn't include the fluid that would be in the torque converter, so my question comes in two parts:

  1. if doing a full change, does anyone know what quantity is required?
  2. Is it better to do a full change or just a drain and refill? Or maybe even to do a drain and refill, run it for a few thousand miles then do another drain and refill?
Reply to
John
Loading thread data ...

The snag as you guessed is you can't drain the TC which contains quite a lot of fluid. Although some have attempted this by disconnecting a pipe to the cooler and running the engine while adding fluid.

But if the transmission is OK, probably just changing some of the fluid will be good enough. If the fluid is very dirty due to contamination from the friction materials, it probably isn't long for this world anyway.

Reply to
Dave Plowman (News)

The correct way is to hook it up to the machine that pumps through fresh fluid and filters it at the same time, your Lexus dealer will do this for a reasonable fee. If you want to do it yourself then drain all you can, put in a couple of litres of fresh Toyota fluid, run for a while, redrain, if it looks reasonably cleam, then fill, if it still looks bad repeat the 2 litres till it looks better. Change every 60,000 is usual.

Reply to
MrCheerful

I've done ZF & GM auto tranny changes and found that if you take the sump off to replace the filter and then remove and empty out the valve body you gets about 7/8ths of the fluid out instead of about half.

I've tried the pump it via the cooler method and it's ok, but you do need to make sure you've got wide bore pipe (too narrow and it just won't flow back in) and a good method of attaching the ends or it gets messy quickly.

Reply to
Scott M

John expressed precisely :

Thanks guys, think I'll go the drain, refill, run for a while and repeat route.

Reply to
John

Are you not going to replace the filter?

Reply to
Scott M

Autos don't generally have filters as such. Or rather the type of filter that cleans the oil - as in an engine. They may have a 'half brick' filter to stop debris entering the pump. If undamaged, just clean if needed.

Reply to
Dave Plowman (News)
[...]

Autodata has no fluid change interval for the auto box, and Google suggests neither does the owners handbook.

Cautious owners in the US advise 30K miles changes. Early cars have a metal screen filter in the transmission sump, but this was later changed to a paper one. These are available, but the metal ones are not.

If the OP wants to maximise transmission life as a DIYer, I would suggest dropping the sump and replacing the filter with a paper one regardless of what is fitted now.

Chris

Reply to
Chris Whelan

full talk through of the whole procedure here:

formatting link

Reply to
MrCheerful

Dunno what you mean by half-brick but 21st Century ZF & GM ones have sealed flat metal boxed filters most of the size of the sump in there. There's usually quite a lot of fine metal mulch stuck to the magnet so I'd not want to do a fluid change without replacing the filter.

As I said before, removing the sump & filter and emptying the valve body drains way more fluid than just draining alone and, with the cost of some of the auto fluids[1] and the palarver of doing half a job, I'd be damned if I didn't change the filter!

[1] the Esso one for 6 speed ZF boxes is horribly expensive with no cheap alternatives.
Reply to
Scott M

Correct. Many don't have a specified service interval.

Cautious owners in the US seem to change oil etc like when it was the old pure base stuff and cost a few cents a gallon. Some every 1000 miles.

The E39 I've just got rid of had about 100,000 miles on it, and 18 years old. Transmission and gearbox oil never ever changed. And both as good as new.

Auto transmission fluid doesn't get bits in it - unlike a synchromesh box can do. Only when things start breaking up. If a decent filter was a help, I'd say the makers would fit one. And list a service interval for it. So the only valid reason to change the fluid would be if it itself had deteriorated in some way. If it looks very dirty, the box has already started to wear out - as everything will - and changing the fluid may not make any difference.

BTW, the final drive in my SD1 has never had the oil changed. Getting on for 200,000 miles and over 30 years old.

Reply to
Dave Plowman (News)

They changed from a 'for-life' metal screen to a paper filter, and in the US dealers replace it as a service item. The metal screen is no longer available as a replacement. Make of that what you will.

Yep, I would concur with all of that. However, there is lots of evidence online that suggests that the box on this particular model is a weakness, hence my advice lifted unashamedly from a number of US Lexus-specific websites.

Chris

Reply to
Chris Whelan

The one on my GM box isn't full sized. But there is a stated service interval for a fluid change. But it is easily cleaned if undamaged. A more sophisticated large filter is probably designed for the life of the box.

Most boxes have no provision for draining. That on its own tells you something.

Reply to
Dave Plowman (News)

The difficulty is to be certain that changing the fluid actually does increase the service life dramatically. Very few people run a car for a high enough mileage to be sure - and even then it's impossible to do controlled tests. Makers of the thing are more in a position to do such testing. And although makers do tend to want extended service intervals for things like an engine oil change, they don't seem to apply that principle to other things at a major service. Brake fluid and coolant still needs a regular change. So why leave out the gearbox if it really does need one?

Reply to
Dave Plowman (News)

Conversely, it's not the most difficult thing to so - handful of M10 cap- heads, and unless particularly portly you don't even need to jack it up - and in terms of the running costs of an RX300 it's not that expensive, so why not do it 'just in case'?

Remember too that the 'for-life' metal mesh screen has been deleted, and substituted by a replaceable paper element, so it seems likely to me that the manufacturers are at least hinting that scheduled replacement has been found to be desirable.

Chris

Reply to
Chris Whelan

I think he means a strainer (gauze/mesh like a tea strainer) that might stop a half brick getting into the pump but not wear material from burnt clutch plates or bits of worn clutch basket splines.

Humm.

Nissan PUT a drain plug on the RE4R01A auto box starting from May 1990.

Perhaps at 125K miles I ought to change it. The accumulator ticks very loudly when stationary and has done for all of the 35K miles I've done.

There is a strainer and each solenoid has a "filter" on its inlet. Pilot filter and lockup solenoid are on top of control valve assy and not easy to get to.

Reply to
Peter Hill

Quite. Usually to prevent lumps of breaking up friction plates. By which time an fluid change isn't going to matter much.

Reply to
Dave Plowman (News)

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.