en11871

Hello,

I am very confused in many opinions in regards to transmission fluid. Some say DON'T flush and some say DEFINITELY flush. Some even said it will DAMAGE the transmission and some say it is WONDERFUL for the transmission. What gives? I just want to know the real story, if there is one. I mean has anyone ever done a flush and their transmission has failed on them? My 2LS has 140,000.

sonyman

It's fine to flush if it's a machine or technique that let's the transmission pump do all the work. What color is your fluid? (Pull the dipstick, and touch it to a paper towel.) Depending on how dingy the fluid looks, you might not need a flush. Are you experiencing any transmission trouble?

Neofate

iTrader: (1)

Flush is fine, you won't damage anything that wasn't already damaged before.

Sony is right, no need to flush if your tranny is clean. Waste of money.

Do some checks yourself before going into a shop for a tranny fluid change.

I would recommend change the fluid out, have a shop do it (easier).. but the flush process is something you can determine if it needs to be done. A shop is 99% of the time always going to tell you you need it.

If you are experiencing Tranny trouble be careful.. Do as sony says -- ask the shop to explain their flush technique -- Be specific on if the pump is involved doing the work and so on. Some techniques can hurt transmissions that are failing to some degree.

That is where your conflict comes in. People who report problems with a flush usually have some sort of problem in the tranny beforehand and the technique used made it worse.. or pronounced it. (Allowed leaks to get larger, broke some seals that had formed over time , moved some gunk to innappropriate areas and so on).

If your transmission is running just fine, again, no worries on the flush.

en11871

Sony,

...at a Lexus dealer...they should have the machine type that you mentioned right? Actually it was suggested that I mix half new fluids in there, of which I did. I guess I just wanted to flush it in the first place. The fluid was pretty black. My car has 140k right now. I have some things coming up in regards to maintainence and would like to do everything. By no means I'm having troubles with my transmission, but I'm pretty sure that the fluid has never been flushed either. Either though it was recently changed half new fluids, as a peace of mind, I would still like to flush. Let me know your opinion(s)...you too Neo. Thanks.

Neofate

iTrader: (1)

I'm not sure if Lexus has a flush, but it is fairly common so I don't see why they wouldn't. Also yes, if you brought it there to get it done, don't worry about your tranny. If it gets screwed up Lexus is the place you want it to be to take responsibility/liability. (It isn't though)

Your fluid color is normal, all you've explained is normal. Flush it out, you might feel some improvement you hadn't noticed, otherwise you'll just have peace of mind.

Bill Dowd

flushing a trany can break old deposits off and they will go thru the trany some times causing problems when they block up small holes that the trans fluid goes through. If you are able to get under your lexus there is a drain plug on the transmission pan that you can drain about 2 quarts of oil from the trans. If you try this it is recommened to do it a few times to get out a lot of the old fluid I think the trans holds about 10-12 quarts of fluid most of it being in the converter. Also be careful not to over tighten the drain plug bolt you might also get a few gaskets that go on the drain plug from the dealer or auto shop. I put a trans cooler on my 91 lexus and pump the trans from the trans cooler pumping 4 quarts of fluid at a time. I also make sure the trans fluid is warm to flow better. I have 200,000 miles on the same trans and I use mobil one synthetic trans fluid. I have seen the lexus trans go 568,000 miles on the same trans with good maintence also don't forget to have someone drain the rearend oil some later lexus's need special oil for the non slip rear ends. Good luck.

sonyman

Call your local dealer and find out. Some dealerships use a BG transmission flush machine that connects to the cooler lines and uses the transmission pump to exchange the fluid. Ask to speak with one of the shop foremen if you can't get a definite answer from a service consultant or technician. Since your fluid is black, it may also be a good idea to drop the transmission pan and have the screen cleaned out. Your transmission uses a reusable mesh screen filter and additionally has magnets inside the pan to trap ferrous particles. There may be some buildup on the screen and magnets that will remain inside the transmission unless cleaned through a pan drop. Normally this isn't needed, but normally the transmission fluid is not allowed to turn black.

Neofate

iTrader: (1)

A bit extra cautious there -- but sound advice,.. You'd have to tell the mechanic to do that if you are incapable of doing this yourself.

If it worries you, just get the fluid changed, regularly. A little remnant of the old will remain, but 95% of it will be new, and it will be fine.

I think an aftermarket trans cooler isn't necessary on an LS 400 -- but it most certainly doesn't hurt .. I'm sure the lower temps help longevity of the tranny. Though it is already bullit proof from the factory (as good as they get anyway). I have 230k on mine, and use NON synthetic in it, and it runs like a brand new transmission.

Bill, since you seem so 'up' on Synthetics. Is the 'leaking seal' principle applicable to a tranny? IE: If I were to switch over to synthetic in my transmission after running regular non synth for 230k,.. Would it cause any problems in the seals/gaskets or whatnot? Or is it 100% safe?


Oh,.. and my Differential fluid is factory. Nothing special about the 94 LS rearend -- How imperative is it to change that fluid? The mechanic said ever change it.. I tend to disagree. Also, same question here -- Synthetic ok in a 230k Diff ?


Thanks,

Neofate

iTrader: (1)

+1


Good advice.

Though for the pan drop I would NOT take it to Lexus. Unless you have alot of money to blow. Take it to a reputable Transmission shop around town and have them drop the pan and take a look, and clean up whatever they can immediately. Then flush/refill it. They should be able to take good care of it.

Dropping the pan isn't a big deal,.. Just requires a new gasket ..

*and they can get a good look at the condition of your tranny*

sonyman

The gasket is FIPG, black RTV silicone.

Neofate

iTrader: (1)

Yup.. A formed in place gasket is still a gasket

I prefer them actually, even though it is messy at times.

sonyman

When properly applied, it's just as good as a paper gasket. I was just making sure that the OP (or anyone else reading the thread) was informed, since elsewhere people have used paper gaskets when in fact Lexus uses FIPG.

Neofate

iTrader: (1)

Good man.

I not only think it is 'as good',.. but can be BETTER than the paper gasket. The FIPG high temp silicone is alot thicker, and molds into each micro groove/pore and can expand and shrink with the temperature. Paper gaskets are easier to work with though

Och

iTrader: (3)

Ok, here's the way I see it.

A simple drain and fill only drains about 1/4 of the transmission fluid - only from the pan. If you do it every other oil change, it will keep your tranny fluid nice and clean.

As far as flush, there are two definitions of flush.

The first is, removing the tranny drain line (the one on the bottom of the radiator), turning the car on, and letting the transmission pump out all the old fluid on its own, while continuously adding new fluid as the old fluid is being pumped out. I believe the capacity of the transmission fluid is around 8 quarts, so when approximately 8 quarts has been pumped out, thats when the flush is complete. You can also tell by looking at the color of the fluid being pumped out - once its the same color as the fluid thats being poured in, thats when the flush is complete. Now, this is a perfectly safe way to flush the tranny, it doesnt do anything that the transmission itself doesn't do under normal operation.

Now I also understand there's a filter in the transmission pan, which is basically a magnet that attracts loose metal shavings and particles, and keeps them in the pan preventing them from circulating through the transmission. It is probably a good idea to remove the pan once in a while, and cleaning these filters.

There's also another way of doing a transmission flush, which I don't recommend. It involves hooking up a machine to your transmission, which will pump new fluid in under high pressure - much greater pressure than transmission pump generates. This can be risky because it can blow seals, and distrurb the metal particles on the bottom of the pan (unless its cleaned out prior to the flush) causing them to mix with the fluid and flow through transmission. Of course this method can take some sludge buildup out, but thats not always a good thing. Sometimes you have seals in your engine and transmission that have already long failed, and the only thing that keeps them from leaking is the... sludge build up. Remove it, and they start leaking.

All in all, I'd say before doing anything, consider this. If your transmission is working nice and smooth, and your fluid is nice and red, then don't mess with it, just do the drain and fill every other oil change, and you're fine. Clean out the pan filters if you're up for getting dirty.

If your transmission is having a problem, then do the first flush method. It will be sufficient if the problem was caused by bad fluid to begin with. However if the transmission is suffering from a mechanical failure, then no matter how you flush it, it wont help. Basically if you've done the first flush method and it didn't help, might as well try the machine flush before you start spending big bucks for a new or rebuilt transmissions.

Bill Dowd

Hello to Sonyman,Neofat and Och I hope other people read your information on transmission service. I also see that I forget to say that it is a good idea to have independent transmission shop drop the pan if the trans oil is black or even dark brown it sometimes means the fluid hasn't been changed in a long time. I see you guys on other posts giving people good advise on how to take care of a lexus and found all of your information very helpful.