Automatic Transmission Fluids (ATF) full 12qt flush, 100 series.
In 2025 I create a AT Alert thread on wire harness and wire housing block. Drawing ATF from AT. We want to check this wire housing block. As a first step and as a PM.
In 2025 I create a AT Alert thread on wire harness and wire housing block. Drawing ATF from AT. We want to check this wire housing block. As a first step and as a PM.
- Park on level ground. Set E- brakes and chock (block) tires.
- Drain ATF from Automatic Transmission (AT) pan, by removing the 14mm drain plug and washer (gasket). Yields ~3 qt. (assumes, at factory set level) from cold transmission. Measure, exactly what comes out and record on ledger. I use a 2-gallon catch bucket, with 1 qt gradation marks. A catch bucket, that is short enough, to fit under AT of stock height 100 series. Note: By raising front of vehicle, we can get a little more from pans drain plug.
- Reinstall the 14mm drain plug, using a new crush washer. As always, when installing any threaded plug, nut or bolt. Thread in/on by hand, all the way. Torque to 15ft-lbf. Mark drain plug, indicating torque to spec.
- Fill AT pan through: dipstick, AT fill hole or ATF return line. With same amount of ATF that came out of AT pan, plus 1/2 qt. (usually ~3 1/2 qt. or more if frt veh. raised) It's okay, at this point to overfill a little. If 98-03, I fill through dipstick. Otherwise, I run hose to fill plug hole. Some, use a pump, filling through return hose.
- Disconnect ATF cooler return hose, form 10mm OD metal return pipe of oil cooler. Hose is attached to metal pipe, that comes from ATF oil cooler, on way back to AT. It’s, found on, RH side near top of engines’ coolant radiator.
- Attach a (IIRC, 3/8” ID) sung fitting clear drain hose, to 10mm OD metal return pipe coming from AT oil cooler. Run other end of clear hose to catch can (drain bucket) that you've marked with 1qt level hash marks.
- Start engine and let it idle with AT in P. Watch to see that ATF is passing through clear 10mm hose, into catch can. As engine runs idling, AT pumps out ATF, using its own pump. We add new ATF into AT as it pumps out. ATF pumps out of AT, faster than can add. I can add ~1 qt, as engine idling, as AT pumps out ~2 qt of ATF. Turn off engine, to stop AT from pumping out more AFT. We should have, 1.5 qt remaining in AT pan. Do not run AT pan dry.
- Add more ATF to AT pan, while engine off. Making up what came out, less what you were able to add in step #7. Bring ATF level back up, to the 1/2 qt overfilled we started with. At this point I’ve 5qt out, 5 ½ qt in.
- Repeat steps #7 & #8, as needed to get out 12 qts. Holding back 1/2 qt on last fill, through dipstick (98-03). We’ll now have on ledger, 12 qt out, 11 ½ qt in. This will leave us ½ low, which we can later add through dipstick, if needed. Without dipstick (04-07), I overfill by ½ qt. ledger will show; 12 qt out, 12 ½ qt in.
- Remove clear hose we ran to catch can, from oil cooler return pipe end. Reattach return hose to oil cooler return pipe. Place clamp, back in position/impressions it left on rubber return hose.
- Check and set AFT level. This must be done at proper ATF temperature (see notes: for proper ATF temp, for year), while engine idling, after shifting and pausing in each gear ~15 to 30 seconds, on level ground. With AT in N or P. 98-03 check with dipstick. 04-up, check by removing check plug, from bottom of AT pan.
- 1998-03, check with ATF #1 temperature at 158F to 176F. I add ATF, through dipstick pipe. Which in 98-03, we should need ~1/2 qt. To get too high “hot range” mark on dipstick.
- 2004-07, check with ATF #1 temperature at 97F-115F. I remove check plug from AT pan. I get ~1/8th qt. if started with level, at factory fill (3/8 qt low).
Warning: Do not load AT, in reverse gear. Doing so may damage transmission. Do shift and hold in "R", but only while engine idling and foot on brake, not raising RPM.
98-03 AT #1 fluid temp, should be at 158F to 176F to set level. I use full synthetic ATF. Since synthetic runs cooler, so can take longer to get to temp range. I set level, with ATF temp #1 near lower range of temp. This allows me to get max ATF in AT. Once ATF temp reached. Simply check the level on AT dipstick. While engine idling, AT in P or N. After shifting through all gears. I shoot for High Hot mark on dipstick. With ATF temp ~160F. I like to nail, the High Hot mark on dipstick.
04-07 AT #1 fluid temp 97F to 115F, level set temperature. I like to also set level, with ATF #1 near lower range of temp (97F). Here we simply remove check plug, while engine idling. We need to see a good flow. Then replace check plug, once flow stops.
04-07 were, underfilled at factory, by about 1/3 qt. We cannot use dash light blinking trick, as seen in FSM. To get indication of ATF #1 at proper temperature. TSB: lowered ATF #1 temp to 97F – 115F.
Once ATF temp reached. Simply remove the "check plug" from AT pan, with a catch can under it. If AT was overfilled, ATF flows out overflow tube. Once ATF flow, slow to just a trickle/drip. Replace check plug with new washer (gasket) and torque to 15ft-lbf. This is done, while engine idling, AT in P or N on level ground. I shoot for ATF temp ~97F.
In 04-07 when checking level, with ATF temp at 97F. If I don't see a flow from check plug, I'll raise AFT temp. If still no flow from check plug, as I near ATF #1 temp of 115F. I'll add 1/2 qt more. To add: With engine off. I add through the return hose (RH side of radiator), with a very large syringe I have I use to pump in ATF.
Which fluid is best for which year 100 series. See your owner’s manual (OM):
1998-02; Dexron II or III
2003; Toyota T-IV ATF
2004-up; Toyota WS ATF.
Use which brand you like, that states it meets your Toyota OM recommended. Best, we don’t mix brands or types. One reason for the full 12 qt flush: Is we don’t know, what ATF have been mixed in over the years.
IMHO any full synthetic ATF rated for the year of your 100 series, type, Is fine. But in the 2004 up. Toyota WS ATF is your safest bet and yields best gas mileage.
ATF I use:
EDIT: 7/27/25 I'm now questioning the use of Mobil MV FS ATF. I've emailed questions to upper level tech support at Mobil, not being answered. CONCERNING! I also know of Toyota Dealership using BG ATF in place of Toy WS, without issue.
In the 98-02 I use Mobil 1 multi vehicle (MV) FS ATF ((Mobil 1 lubes, are all full synthetic (FS)). "I'd use in all years, if Mobil 1 would rate for them all" But they don't.
2003, Toyota IV ATF.
04-up, I had used Toyota WS ATF.
Interesting: The Toyota ATF are made, in a joint partnership Toyota/Exxon Mobil plant.
Mobil 1, does have an approved ATF for WS. But, for some reason, NOT sold in USA.
Notes:
By using a ODBII device wirelessly hook-up to smartphone. The ATF temp can be read while under the hood or under the vehicle. In the 04-07 this is super helpful.
Right (RH) side. It’s your RH, when sitting in drivers set.
Some say flat side of crush washer (gasket) out, other say in. I’ve not seen, leak either way, when new properly torqued down 15ft-lbf.
In 04-07, I start procedure with engine cold, warm at most. Since I fill plug, is near exhaust pipe. Which hot exhaust pipe, will burn my arm reaching up past exhaust pipe to fill hole.
I use tech streams (accurate), to read ATF temperature. Or Use IR gun, shoot within 3” of center of AT pan (not accurate). To see ATF #1 temp. Using IR gun, OAT and radiated heat from surrounding effect read on IR gun.
FWIW notes:
Using a torque wrench.
Hold handle at designated point (near back of handle) with one hand. Other hand can’t touch wrench, but can touch/hold extension between wrench and socket. Always turn slowly to ft-lbf spec, once and stop.
Drain & fill D&F vs full 12 qt flush.
The D&F is considered safe. Draining the AT pan, and add back same amount of ATF. Safer, in that, if the AT is gummed up with crud/insoluble in fluid, and clutch plates friction material trashed. Full flushing, removes insoluble that were creating friction in fluid, acting as if clutch friction material. Then, clutch plates loose friction and slip. Which reveals, a bad transmission. Accorded to a top transmission shop. Toyota clutch friction pad. Are glued to clutch plates with water soluble glue. Toyota TSB, indicates Toyota WS is hygroscopic. By warning us, to not use bottles that have been opened. This is arguable, one of the reasons 2004 up are sealed ATs.
By doing D&F, theory is. Refreshing the AFT by replacing ~25% at a time. Will help clean gunk, insoluble and moisture form fluid gently. Bottom line. IF AT valve and clutch plates, are in bad of condition. The AT will likely fail regardless. just happens slower with D&F.
The first step in either a D&F or full 12 qt flush. Is draining the pan. The fluid can be inspected at that time. If we find it really bad looking and smelly. Then just do a D&F, repeating every few thousand miles. If that makes you comfortable.
Here’s number one issues with the Toyota recommend D&F.
Unless, one, has had their 100 series, since mile one and done all ATF D&F DIY. With only Toyota specified ATF for year. Very likely, a mix of brands/types of AFT are in the AT. Mixing fluid, is never a good idea. It is what leads to fluid issues, in the first place.
I do mostly full 12 qt flushes. I have in the past, done a few D&F. Either was very low miles, I felt AT never touched (a virgin AT). Or I did have some concern with condition of condition of AT. But that was only about 2% of the time.
98% of the time. I do full 12qt flushes. If I feel the AT/ATF, is so bad off. A full 12 qt flush kills it. It’s was a bad AT. We just as well, findout now as 500 miles from nowhere.
To date, all full 12 qt flushes I’ve done or know about being done correctly. Have only improved performance and reduce ATF operating temperature. Not one has failed after a full 12 qt..
Some of these AT, do show signs of being questionable condition (weak AT). Sign is, as I bring ATF temp up in shop. It very quickly increase and even pass my target level sitting temp. This is most likely, a sign of excessive plate slippage and wear. These AT, still saw improvement with the full 12 qt flush and all are still on the road today to my knowledge.
I’ve seen many, 100 series with AT shifting and or overheating issues. Each I’ve corrected by a full 12 qt flush. Each had in its history D&F, before I flushed.
All 1998-2007 AT pans, have drain plug. Only 2004-up pans, have a check plug. Same, washer (gasket) for all.
For drain plug, I use 14mm socket. Check plug, I use 5mm hex socket. Torque 15ft-lbf
Only 2004-up have check plug (no dipstick). It plugs, a straw sticking up in pan a few inches. If ATF low, we only get a drip at best, when check plug removed. Since level below top of straws opening. If level in pan, high. ATF is then above top of straw sticking up in AT pan. So then, ATF flows out straw, when check plug is removed. AT #1 fluid temp, needs to be 97F to 115F, when setting level in 2004-07. Tip: Overfill AT before checking (check plug) ATF level, by 1/2 qt. If underfilled, we don't know how much is needed when check plug removed. As in all years: Check when on level ground, engine must be idling, AT shifter in N or P, after shifting through all gears.
Crush washer (gasket) P/N # 33178-30010, With 5mm allen wrench in check plug. Drain plugs, is 14mm 6 point nut. I use 14mm socket on.
Return pipe & hose, are on RH side of radiator. The oil cooler return pipe, passes through radiator support into engine compartment area. Return, is the top pipe, which rubber return hose is attached to. I tap in at return pipe, by attaching my 3/8" ID clear hose, and run to catch can.
2 gallon catch bucket.
The return hose can just be left open (as seen below), as we flush. It can also be used to add ATF to AT. Notice, the impression in rubber hose, the clamp left. When done with flush. Place hose back on return metal pipe and then clamp back in exact position in rubber hose' impression.
AT with dipstick 98-03, I fill through dipstick tube:
Fill hole LH side of transmission to transfer case adapter. I've a threaded adapter with hose attached to it, threaded into fill hole. Just a hose, stuck in fill hole, in is fine.
Hose run back to fill hole.
I use OBDmx on my smartphone, to watch ATF #1 temp. It wireless and easy to take I need it. ATF #2 temp raises faster than #1. I like to time, so that ATF #2 is dropping back, near ATF #1 temp (equalizing).
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read, the Owner's Manual. We know, Toyota recommends we rinsing the radiator fins.
