Transmission drain and fill High mileage

No matter the high miles I never power flush but I do flush. I just let the transmission pump do it.

Pan down and cleaned, new filter, and on an AB60; a new solenoid D. Pull a return-from-the-cooler-hose and use a length of clear tubing to direct the old fluid into a clear 1 gallon container. Add two quarts more than was drained out and start the engine. When the gallon container is full turn off the engine, empty the gallon container, and add four more quarts of ATF. Repeat until the fluid coming out looks like the fluid going in. Put the return line back together and check the final level. It's faster on a lift and/or with a a helpful helper but I just did one solo.

I do it on anything I buy used - that way I have a known-baseline for the future. The world is full of fools and The Stupid - who knows what kind of nonsense the previous owner was up to? Or when? <g>

My opinion is that new fluid is always better than old fluid. I just cannot see that leaving old fluid is ever better than replacing it. If anything is going to hurt the transmission - my money is on it being the Old rather than the New fluid. <g>

Oh that reminds me: I told someone else earlier that I would measure the height of one quart in an AB60 transmission pan. I better go tell him the results.

 

I’ve been watching this tread with interest for quite some time. Not saying anybody is right or wrong. Just throwing another opinion out there (which is not even mine.) I have a close friend that owns and runs a small trans shop. Been doing it over 25 years now. I bounced the same age old question off of him about high mileage and old fluid with a modern transmission. This is what he told me: if they get a transmission in for fluid change on a high mileage engine, they pull the pan for a thorough exam. He said they look for metal, sludge, deteriorated fluid. Based on years of experience on what he sees, he says yes or no to the change. He did say 80% of the time he changes fluid but weekly will decline a fluid change due to the above conditions.

 

So, basically 1 in 5 of incoming vehicles to his shop fits the bill of what I've brought up in other threads. That is, the horror stories we hear, borne of:

• Someone did something stupid and/or their transmission is behaving funny as if on edge of failure (slipping, weird shifts, missing gears, etc.)
• Quietly take it to the local shop for a fluid exchange and/or some form of service
• Transmission fails a short time later, as it was destined to do anyway because of [stupid action by owner] or [transmission in poor health already]
• Blame the transmission shop and/or blame the transmission being higher mileage w/unknown service history

I suspect this is probably the wild majority of cases where it's happened. While the "detergents in the new fluid broke free a deposit that jammed up a passageway or solenoid!" is an awesome, potentially plausible reason why a full fluid exchange could do this, I legitimately doubt it's ever actually the cause.

That's incredibly smart on his part to be proactive, but it also must be time/labor intensive, I hope he's charging an hour labor on each of those preinspections.

 

Because I am tired of looking for that other ATF thread - which had an very interesting post about the need for absolute precision in adjusting ATF fluid level / the impacts of thermal expansion on ATF levels - I'll just write it here:

I recently had an AB60 pan off for inspection / cleaning (found just the slightest gray dust on the magnets at 100,000 miles since last service) and afterwards added 1 quart to the clean pan. This produced a 1/2" level in the pan. The top of the level-checking-overflow tube is 1 1/2" up from the bottom of the pan.

I volunteered to do that because a gentleman in the other thread had worked out the thermal expansion characteristics and determined that they are pretty much lab-grade differences only. That is: the difference in volume between 70º ATF and maybe 130º ATF was slight. I believe his intention was to point out that the has-to-be-at-exact-temperature-to-check-level mandate, while accurate, meant relatively little in actual field application. I had earlier come to the same conclusion on my own, but via the internal swirl of how my brain works, rather than by three decimal place calculations. <g> I well understand that Toyota has to supply an exact target to aim for, of course, but I'm sure they were extremely reluctant to offer any acceptable tolerance. <g>

I bubble-leveled the frame by the way. By myself I didn't use a scanner but I did have an insulated thermocouple on the out-to-the-radiator line.

When I put it all back together this time I also added two quarts over what I thought to be full and watched it drain. To start out the flow column was a cylinder the same diameter of the overflow plug's threaded hole. It only lessened after between 2-3 pints had drained. For the last pint or so it changed quickly from full-stream to pencil-sized to almost-pencil-lead size. My point being that so long as the draining fluid column is not full-stream - you are within a pint of perfect. Waiting for the last dribbles to come out seems meaningless in my opinion. I also know from previous experience that even with low ATF levels a surprising amount of drips still come out the overflow - due to turbulence is all I can picture.

Even a full quart over full would only increase the ATF fluid level 1/2" above the top of the overflow tube and any reduction in the overflow rate means you are lower than that. So my conclusion is that to be correct level you have to have a slight stream out the overflow - not just drips - but not a full stream.

Now while I do agree that you can't hit a target that you don't know or aim for - there are other rings outside the bulleye that are still on-target. <g>

 

I'm not a mechanic...

If the transmission is so fucked that it requires a bunch of clutch material, sludge and what all else in the ATF to continue to operate then why remove even a quart or two of this needed crap in the ATF, just to see what happens?

 

Good to know for someone like me who has always had a fill port and dipstick for ATF service. But no longer with a 2006. Sigh

 

God, the wealth of information in that fantastic thread makes me so jealous that one doesn't exist for 2nd Gen's. Like, im not qualified enough to know whether that information still applies to 2nd Gen Tundra, so I would naturally use third-party oil and air filters, since that's what everyone does on every car I've ever seen. It's hard to know what you don't know.

 

I hear everyone screaming about not dropping the pan to clean it. but isn't there a magnet on the bottom of the pan? so we pretty much just live with the magnet being full of metal debris? or is there a way to clean it without dropping the pan?

just a thought

 

If there's any substantial buildup on your pan magnet(s, since I think there are more than one), dropping the pan is the least of your worries.

 

Funny I didn’t even see this thread all day while I was doing my drain and fill. I always just feel it out when tightening drain plugs. I could feel the trans pan was a little softer metal so I kinda eased off on the torque. Glad I did. I was probably 1/4 turn from stripping it. Yikes.

 

Yep, that and the transfer case drain plug are very easily stripped

 

I'm curious, why is it that these kinds of bolts are not given torque specs? If they're so prone to stripping that it's a commonly-known problem, why have car manufacturers not published a recommended torque that is safe? Or have they, and it's just that no one bothers looking it up?

 

It's not the plug to housing that strips, it's the tool to plug interface that strips. A large Allen key isn't the best way to transmit torque.

 

The only thing I can possibly think of, and I'm not an expert on the subject, just thinkiing about it logically: You're dealing with a bolt that holds lubricant. Lubricant getting into threads is a recipe for over-torquing, this is why I never use antisieze on my spark plugs.

Say your torque spec is 30lbft. With no lube, the tension on the threads as you approach the actual value of 30ftlb will be reached at the appropriate time. If you lubricate that thread, when you go to torque the fastener, the lubricant acts as a friction reducer (which is why we use it!), and when you're actually reaching 30lbft of seated force, the lubricant will still be reducing friction, causing the bolt to go in farther than it normally would.

Like I said, this is just my take on it. I could be totally wrong. But I've heard so many people who've added lubricants onto threaded stuff and stripped them due to overtorquing more times than I can count on fingers and toes in my lifetime. I won't use the stuff unless the OEM calls for it, or there's a compelling reason. And I never use lubicants or antisieze it if the receiver hole is in an aluminum/alloy housing. Only steel.

To that point, if the receiving hole is cut into alloy/aluminum and the fastener is steel, I'm always going to be more gentle with my torquing. For example, with our trucks:

• Valve cover bolts - the cylinder head is alloy
• Spark plugs - the cylinder head is alloy
• Transmission pan bolts - the transmission body is alloy
• Transfer case bolts and plugs - the case housing is alloy

Rear diff plugs? IDGAF, steel housing, steel plug. I want to say the front diff housing is same, but I don't recall, so I'm not going there at the moment

 

There are manufacturer torque specs. I believe some have been torquing to the spec when it strips. Likely due to factors shifty explained well. Take a less experienced/skilled person like myself, but wanting to be thorough and precise, we may follow the torque specs. Not having learned yet the importance of context and application for that procedure. All things so valuable and shared in this forum.

To say nothing of someone doing it themselves for the first time and removing a bolt/plug that was over tightened by someone at the quickie lube who surely cared a lot. Or a previous owner. My transmission plug stripped trying to remove it when the truck was new to me. Not a well designed plug with that small Allen head, imo

 

Torque specs for every material, size, and thread bolt is available in mechanical engineering manuals. And on line although I don't know where exactly.

BTW: the engineering specs are often separately listed as being for lubricated and non-lubricated threads. What often counts in terms of holding/power is bolt stretch but what is measured is torque - which varies by resistance to turning.

 

Days late for the OP but I did my first drain and fill this past August (2025) at 375k (ish) miles. I had owned the vehicle for 150k miles leading into that and never touched it. No clue what the prior maintenance on it was so take it with a grain of salt.

No transmissions issues before or after complete drain and fill. There was plenty of shimmering in the bottom of the pan however which should probably give me cause for worry but I have other stuff needing repairs before even thinking about the transmission

 

Ah, fair enough, good answers all around, than you. I think having lubrication on the threads is definitely a major culprit, but also, I didn't realize people were talking about the drive being what strips. I always assumed it was the threads in the aluminum pans that were stripping, not the bolt heads themselves.

 

Was defnitely talking about the threaded holes, not the fastener/bolt threads or heads.