Change transmission fluid? (1 Viewer)

[Drecolkris]

I just got a 2000 LC with 293K. Transmission has never been opened up. Was cared for by an old school Toyota mechanic who told the owner to never open it up unless problems arose.

No leaks and it shifts well with no problems.

Leave it as is? Or open it up to change out fluid?

 

[nissanh]

How does the oil looks like? Brown?
I think the best is to drain and fill than a complete exchange/flush.

 

[SteveH]

At least you have a dipstick. Wipe it on a clean white towel and smell it. If it has truly never been changed, it will be dark cherry red and may smell burned.

I would drain the pan, fill it with as much as came out, and then pull a trans cooler line, start it, let the engine run until you pump out about 2 quarts, shut the engine off, add 2 quarts, and then repeat until clear, pink, new ATF comes out of the cooler line. Reconnect, run hot, check level, and you are done.

 

[TexLexican]

Drain and fill every oil change. You’ll get about 3 qts out of the pan.

 

[Malleus]

Never replacing fluid in an automatic transmission is the worst voodoo old wives' tail. The fluid does not last forever and flushing it will remove crap from the case that doesn't need to be there.

You don't need to open anything to replace the fluid. You can use the transmission pump to pump out the old fluid and pour new fluid in the dipstick tube. Replacing the pan fluid is not cost effective - you won't get enough fluid out to make a difference. There is less in the sump than in the cooler circuit.

Remove the top hose form the cooler at the front right corner of the engine compartment and connect a clear drain tube to that nipple. Run that tube into a clear container (you'll need several gallon containers) marked so that you can see how much is coming out. Put in as much as is being pumped out, starting and stopping the engine if necessary to change containers. When you've replaced 3 gallons, you're done.

Do not overfill the transmission. If you do, you will have to pull the drain plug.

 

[TexLexican]

Never replacing fluid in an automatic transmission is the worst voodoo old wives' tail. The fluid does not last forever and flushing it will remove crap from the case that doesn't need to be there.

You don't need to open anything to replace the fluid. You can use the transmission pump to pump out the old fluid and pour new fluid in the dipstick tube. Replacing the pan fluid is not cost effective - you won't get enough fluid out to make a difference. There is less in the sump than in the cooler circuit.

Remove the top hose form the cooler at the front right corner of the engine compartment and connect a clear drain tube to that nipple. Run that tube into a clear container (you'll need several gallon containers) marked so that you can see how much is coming out. Put in as much as is being pumped out, starting and stopping the engine if necessary to change containers. When you've replaced 3 gallons, you're done.

Do not overfill the transmission. If you do, you will have to pull the drain plug.

I’ve heard many people say that if you haven’t touched the fluid and you’re over 100k miles do not drain all at once. But that could be an old wives’ tail as well.

 

[Chrisek]

Personally I change my drivetrain (transmission and all 3 diffs) every 30,000 miles. Most manufacturers (trucks) say every 60k is fine.

 

[Malleus]

I’ve heard many people say that if you haven’t touched the fluid and you’re over 100k miles do not drain all at once. But that could be an old wives’ tail as well.

I'd be curious to know what the reason is, beyond "I think that's the way I'd do it..." That's kind of like only washing part of your car at a time.

There's no magic inside an automatic transmission; it has wet clutches whereas the manual transmission has a dry clutch. It has planetary gears instead of spur gears, but that's just to save space (planetaries are the most compact gear trains - they also hurt your head more), since they have to also have an operator (fluid pressure within the fluid passages)- since you're not doing the gear changing with your foot.

Wet clutches slip more, so there has to be more of them. More parts to wear, more wear happens. That clutch friction material has to go somewhere, and the somewhere is in the fluid. You could strain it out, but the fluid also has detergents in it (to wash the friction material out of the clutch packs), which break down over time, so that's not really cost effective.

The more friction material you leave in the fluid, the less effective the clutch friction surface(s) are at holding any given gear. The less securely the gear is held, the more the other clutches in the pack slip, and the more friction material winds up in the oil. The cleaner the oil the better the clutch plats hold against the steels.

That's simplistic, but not far from the rest of the story, as Paul would say.

 

[Les Summer]

anyone know how much room for error there is for overfilling a 100 LC?

 

[Chrisek]

anyone know how much room for error there is for overfilling a 100 LC?

Since yours has a dipstick, You’ve got room. Doing it yourself, it is actually difficult to drain the whole amount of fluid. Just have patience when refilling Switch to quart/liter size bottles (or only use them) and it will be difficult to overfill as you will get on the dipstick before overfilling.

 

[BullElk]

Wonder how many more trouble free tranny miles I could get if I changed clean fluid as much as y’all recommend. If I did, my Hundys would become high maintenance vehicles.

 

[Les Summer]

Since yours has a dipstick, You’ve got room. Doing it yourself, it is actually difficult to drain the whole amount of fluid. Just have patience when refilling Switch to quart/liter size bottles (or only use them) and it will be difficult to overfill as you will get on the dipstick before overfilling.

I recently did a drain of about two quarts out of the dipstick pipe.

Since yours has a dipstick, You’ve got room. Doing it yourself, it is actually difficult to drain the whole amount of fluid. Just have patience when refilling Switch to quart/liter size bottles (or only use them) and it will be difficult to overfill as you will get on the dipstick before overfilling.

My fluid is currently past the highest "Hot" notch with the vehicle warmed up and the fluid cycled. I'd say about a 1/4 inch. When I check my stick I make sure the stick is saturated on both sides with a full puddle of fluid on each side of the stick, and not just fluid creeping up the edges, which I don't count as part of the reading from the stick, if that makes sense.

 

[Malleus]

anyone know how much room for error there is for overfilling a 100 LC?

The answer to your question is an understanding of why overfilling causes problems in a pressure operated transmission. ATF expands as it heats up and there is air in the case to allow for this expansion. Normally only a little fluid mixes with the air, and the entrained bubbles rise out of solution in the cooling circuit and torque converter.

If too much fluid is retained in the case, it'll mix with the air, and the air won't have anywhere to go. Unlike hydraulic fluid, air is extremely compressible and air entrained in a fluid reduces the fluid's compressibility directly as the volume of entrained fluid increases. In other words, the more air you mix with the fluid, the lower pressures you develop and the more the clutches will slip. Remember, it's the fluid pressure that keeps the steels and clutches in contact. When the fluid pressure decreases, or the distance the clutchpacks can compress increases (which happens as the clutches wear), the "sticking force" keeping them together, and therefore keeping that gear ratio engaged, is lessened.

The more clutch slippage you have, the shorter the clutch life, and therefore the shorter usable transmission life, you have. Automatic transmissions are highly dependent on the amount of fluid in them to operate properly. That's why there's a HOT mark on the dipstick, and you're supposed to check the fluid level when the fluid is at operating temperature.

The point about not having a dipstick (which this doesn't address) is marketing, not science, so I'll leave that alone.

 

[Les Summer]

The answer to your question is an understanding of why overfilling causes problems in a pressure operated transmission. ATF expands as it heats up and there is air in the case to allow for this expansion. Normally only a little fluid mixes with the air, and the entrained bubbles rise out of solution in the cooling circuit and torque converter.

If too much fluid is retained in the case, it'll mix with the air, and the air won't have anywhere to go. Unlike hydraulic fluid, air is extremely compressible and air entrained in a fluid reduces the fluid's compressibility directly as the volume of entrained fluid increases. In other words, the more air you mix with the fluid, the lower pressures you develop and the more the clutches will slip. Remember, it's the fluid pressure that keeps the steels and clutches in contact. When the fluid pressure decreases, or the distance the clutchpacks can compress increases (which happens as the clutches wear), the "sticking force" keeping them together, and therefore keeping that gear ratio engaged, is lessened.

The more clutch slippage you have, the shorter the clutch life, and therefore the shorter usable transmission life, you have. Automatic transmissions are highly dependent on the amount of fluid in them to operate properly. That's why there's a HOT mark on the dipstick, and you're supposed to check the fluid level when the fluid is at operating temperature.

The point about not having a dipstick (which this doesn't address) is marketing, not science, so I'll leave that alone.

Sounds like you work on them for a living. I understand enough of what you said, although it's a bit of long follow for me.
Anyway, I notice two notches for HOT on the stick. I assume when I'm at full operating temperature I should be seeing fluid only reach the top notch on the stick and not a bit further. I'm a 1/4 inch past that, which is maybe about one glug of trans fluid too much that put me there. I sigh, I've been overfilling for a long long time like this. I never thought that little bit could really matter that much..

 

[beatle_bayly]

Change it. I believe the filled-for-life spec didn't begin till the A750 so even Toyota had a change interval.

 

[Dirt J]

Change it. I believe the filled-for-life spec didn't begin till the A750 so even Toyota had a change interval.

Maintenance interval is every 45k if operating under "normal conditions", or 30k under "special operating conditions", per Toyota maintenance schedule for 2000 model year (A343F).

 

[Zooguy]

Previously in this thread it was stated that it takes about 3 gallons using the method where you unhook the upper transmission line going into the radiator/cooler.

That process going back and forth starting it stopping it sounds like it can be rather tedious and unfortunately I have a tendency of being impatient. I have a 1999 Toyota Land cruiser that just rolled over 200,000 miles and the transmission fluid is still red but quite dark not yet Brown.

My transmission dipstick has an o-ring at the top of it and a little spring lock clamp holding the dipstick tube down in the hole. I can only assume this functions a seal. To keep dirt from intruding into the transmission through the dipstick.

So if I have a seal there and I unhook the line that feeds the trans cooler up front as the fluid is being pumped out one could assume air is being pulled in through the trans cooler through the return line into the pan as the pickup tube inside the pan draws fluid up to the pump.

Assuming that is correct and has a good hydraulic suction. .... WOULD IT BE POSSIBLE to disconnect the lower transmission hose as well hook up a clear tube and submerging that into let's say a 5 gallon bucket of transmission fluid. Start the Land cruiser and just let it run until the fluid coming out of the upper hose (drain tube) is clean and fresh looking? Then turn off the motor and reconnect the lines to the trans cooler?

With having a 5 gallon bucket that should be more than enough fluid. so that mitigates the risk of accidentally "running dry" and take substantially less time.

Has anybody attempted this or could any Toyota technicians/mechanics share their opinion on it?