anyoldiron

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470reasons

I did a fluid exchange "from the top" on my external trans cooler equipped 2004 GX470 this past Monday. Purchased this GX with 108,000 miles on the odometer and now have 155,000 miles on it. I could not find any reference to a trans flush in the MyLexus maintenance history. The previous owner seemed to have all the servicing done at Lexus (even the wiper blades). Figured the GX must surely be due for an ATF exchange by now. When I drained the pan, the old fluid coming out looked good and smelled good. I almost stopped right there. But, I had already purchased all the new ATF and had psyched myself up to do the procedure NOW. Here are my observations and comments on the procedure:

• Buy a cheap BIG blue tarp and drive the GX on to it. Whatever method is used to change out the ATF, IT WILL BE MESSY!
• Hardly any fluid came out of the cooler hose when it was disconnected from the oil cooler. NO fluid came out of the disconnected hose while doing the procedure, no need to plug it.
• I used 1/2 ID thin wall tubing for the drain hose. 3/8" ID would have worked better. Probably would not have needed the hose clamp with 3/8" ID hose.
• The fill hose was about 6' of thick wall clear plastic 3/8" ID hose. The thick wall hose did not kink when routing the hose up through the fender well. The hose can be tucked up under a corner of the exhaust heat shield to keep the hose from melting.
• A plastic garbage bag was used to protect the fender. Not a good idea! The ATF melts trash bags! I was lucky and didn't damage the paint. Maybe a chunk of blue tarp would work better?

Procedure I Used to Exchange The WS ATF.

Make sure fill, overflow, and drain plugs loosen up before going further!

Drain trans pan and refill pan (through funnel and hose) with same amount of fresh fluid. (Actually, I put in about 1/2 quart extra fluid.)

1. Connect drain tube to upper oil cooler hose barb. Place drain tube in a plastic gallon bottle labeled "OLD".
2. Set your phone timer to 23 seconds.
3. Start phone timer.
4. Start GX.
5. With foot on brake, at idle, run shifter through all transmission detentes twice and return shifter to 'P'. When timer beeps shut off engine. Approximately 1.5 qt old ATF will be in the bottle. Slowly pour the same amount of new fluid into the funnel. Repeat and repeat and repeat until new fluid comes out of drain hose. (I added a little extra fluid during each cycle.)

• The procedure for checking the ATF level at the proper temperature is explained elsewhere on the forum. When I did the final level check, I was about a quart over the correct level. No harm done I guess.
• Rechecked the ATF level after 25 miles of driving. A few drops came out the overflow port. Added some fluid and redid the check. Just about all the fluid I had just added poured back out. The level must have been spot on the first time!
• My GX has a lift kit, so I wasn't sure how that would affect the fluid level check. I placed a magnetic level on a frame rail. The GX wasn't level so I had to drive up on some 1.5" wood blocks.
• Install new crush washers on the drain and overflow plugs. Buy extras in case rechecks are required. Toyota part number for the drain and overflow washer is 35178-30010.
• The overflow plug was the hardest to remove. The plug wouldn't budge and I was worried about stripping the socket. I dug out all the dirt with a jeweler's screwdriver to get the 5mm bit to seat all the way into the plug. It came out! I replaced the overflow plug. Toyota part number 90341-10021.
• Got the fill plug O-Ring at Ace Hardware. The Ace O-Ring is slightly larger than the original but should work fine. #12 O-Ring, 13/16 x 5/8 x 3/32 (Correct size is 3/4 x 5/8 x 3/32)
• This is crazy, but with spillage and overfilling, I ended up using 17.5 quarts of WS ATF. The Toyota parts counter guy said a normal full ATF exchange takes 16.5 quarts, so I wasn't far off. Be prepared with enough fluid on hand if you're doing this procedure! I had to go back and buy four additional quarts, as I thought 15 quarts would be enough.
• The "from the top" method sure beats using a hand pump on quart bottles!

Well, that's my input on the subject. Hope this helps!

Drain hose connected to external transmission cooler top hose barb. Plastic hose connected to oil cooler. No flow from disconnected hose even with engine running. No mess!
Funnel on side of GX. New fluid goes in here.
Level on passenger side frame rail. The aftermath!

anyoldiron

my mistake, need glasses

chiph9

This Taco also has a "sealed for life" transmission. And the fluid is scary bad.
Do regular transmission fluid changes on your GX if you want it to survive!

Note that the GX refill procedure is different from this one.

Chip H.

borgunit

From a certified Toyota mechanic.