To change or not to change.

[AHTex]

Hey all,

Ive seen a lot of info out there, but figured Id ask specifically for my situation. Ive been slowly bringing my 2wd,97, 2.7 auto back into drivable shape after a 4/5yr hiatus from driving. Ive gone through most of the mechanicals and have been driving it daily. About a week ago, the plastic top of the radiator cracked, so I picked up an oem from the dealer and replaced. In doing so I obviously had to disconnect the trans lines. This is when I noticed that my atf was a bit dark, almost brown. No weird smells or anything. My initial thought was to do a drain/replacement of fluid, but now im second guessing myself. Ive had no issues with shifting or anything indicating a trans problem with 266,000 on the odometer. I do need to replace what I took out when changing the rad, but thats it. So my question is, is this a situation where if it aint broke, dont fix it? Ive heard horror stories about tranny failure after changing the fluid. What do yall think?

 

[spartacus]

Old atf looses it's potency and gets impure with clutch material over time. Changing it or doing a full flush with dex-iii should be fine. You can also drop the pan and replace the atf filter.

 

[mtbtim]

I would not do a full flush if your fluid is looking dark. At most, I would just a drain and refill exchanging out around 4-4.5 quarts.

The risk your talking about is real. For a trans that has been abused with infrequent fluid changes, excessive wear has occurred. That dirty fluid could be holding suspended friction material that your trans is relying upon to shift properly and not slip. Also, new ATF has excellent detergent qualities. The fresh detergent could act upon sludge build-up in the trans, breaking it free and that sludge could get trapped in fluid pathways, like in the valve body and starve the trans of fluid.

If it's a case where the trans is in bad shape and the clutches are on their last legs, a fluid change could be the end of your transmission because it was relying on that suspended clutch friction material. But, your trans in this scenario was probably close to having major issues anyway and who knows how many more miles you could have gotten out of it.

So, entirely up to you, but if it were me, i'd risk the drain and refill and see how it goes from there. I'd rather know if my trans is on it's last legs because I take long road trips and wouldn't want to get stuck 3 states away from home needing a new transmission.

 

[thennen]

I would not do a full flush if your fluid is looking dark. At most, I would just a drain and refill exchanging out around 4-4.5 quarts.

The risk your talking about is real. For a trans that has been abused with infrequent fluid changes, excessive wear has occurred. That dirty fluid could be holding suspended friction material that your trans is relying upon to shift properly and not slip. Also, new ATF has excellent detergent qualities. The fresh detergent could act upon sludge build-up in the trans, breaking it free and that sludge could get trapped in fluid pathways, like in the valve body and starve the trans of fluid.

If it's a case where the trans is in bad shape and the clutches are on their last legs, a fluid change could be the end of your transmission because it was relying on that suspended clutch friction material. But, your trans in this scenario was probably close to having major issues anyway and who knows how many more miles you could have gotten out of it.

So, entirely up to you, but if it were me, i'd risk the drain and refill and see how it goes from there. I'd rather know if my trans is on it's last legs because I take long road trips and wouldn't want to get stuck 3 states away from home needing a new transmission.

Tim, I don't know anything about transmissions, and your explanation brought a question to mind. In light of what you're saying, would a slow process of 'dilution' be another option? For example, drain a quart and add a quart, drive for some period of time, then do it again, for X number of times? You would never end up with a full flush, but over time would increase the clean fluid ratio. Might also let you notice small changes earlier. Again, I know nothing other than what I read here.

 

[mtbtim]

Tim, I don't know anything about transmissions, and your explanation brought a question to mind. In light of what you're saying, would a slow process of 'dilution' be another option? For example, drain a quart and add a quart, drive for some period of time, then do it again, for X number of times? You would never end up with a full flush, but over time would increase the clean fluid ratio. Might also let you notice small changes earlier. Again, I know nothing other than what I read here.

It's harder to just replace one quart at a time unless you disconnect the trans cooler return hose, run another hose to the cooler nipple, start the engine, run one quart out into a container with graduated volume markers, re-hook up the cooler line and then add a quart into the trans dipstick tube. This is the process we use when doing a DIY flush. Trying to drain just one quart out of the pan would be a very messy operation because you have to put the drain plug back in while fluid is still pouring out.

The dilution process does work really well to keep your fluid in good shape. I do a drain and refill on my trans pan every 10k miles. There's no need to do a full flush ever if you do regular drain and refills.

So, if somebody wanted to be really careful, they could drain out just one quart out like I described. It's just more work than simply opening a drain plug and exchanging out 4-5 quarts.

In the OPs case, if he did want to start renewing his fluid the safest way possible, 1 quart at a time would be safer than a drain and refill of the pan and certainly leaps and bounds safer than a full flush. Doing a full flush would be taking your life savings, putting it all on red and spinning the roulette wheel.

Since it relates, here's our video of doing a DIY Trans Flush:

<iframe width="560" height="315" src="https://www.youtube.com/embed/RumPXivBlk8" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

 

[spartacus]

I vé heard of Trans back flush causing issues in transmissions but the myth that old atf keeping your transmission working because of buildup is a fallacy. A damaged transmission on its way out is inevitable. Speculating how many miles before it fails debatable. Good Atf is better at lubricating and heat dissipation which is the key.

 

[mtbtim]

I vé heard of Trans back flush causing issues in transmissions but the myth that old atf keeping your transmission working because of buildup is a fallacy. A damaged transmission on its way out is inevitable. Speculating how many miles before it fails debatable. Good Atf is better at lubricating and heat dissipation which is the key.

Well, there's lots of people who would disagree with you including myself. I've done lots of research on this subject and the findings I have found show their is a significant risk changing out the fluid on an abused transmission. And, it wasn't just situations where people got a power flush.

There's just way too much information out there to back up what I'm saying. Anyone who bothers to do a search will find plenty of information to support my claim.

 

[TheGrasshopper]

OP, I was in a situation very similar to yours. My trans fluid was very dark (and low) with 300k miles on the truck. I am not the original owner, and I had no idea when or if the fluid had been changed. I did a drain and fill, and got about 4 qts out. This noticeably smoothed out my shifts. I have put 15k miles on it since then, and it still shifts great.

Edit: I also did a drain and fill on a couple of other 4runners with about 250-260k miles with no issues. One of them had the fluid changed one time in the past. It is a good idea to change the transmission drain plug gasket. This is a different gasket than the oil drain plug, but I used an oil drain plug on my runner because that is all I had at the time. I used Valvoline Max Life full synthetic ATF. WalMart online had the lowest price.

I have heard of some people saving the dirty fluid in case the fresh fluid causes slipping. You can also try a transmission fluid friction modifier if you have slipping. These would only be band aid fixes to a larger problem, of course.

 

[spartacus]

Well, there's lots of people who would disagree with you including myself. I've done lots of research on this subject and the findings I have found show their is a significant risk changing out the fluid on an abused transmission. And, it wasn't just situations where people got a power flush.

There's just way too much information out there to back up what I'm saying. Anyone who bothers to do a search will find plenty of information to support my claim.

I have and what I found was more of opinion, speculation, conjecture and not definitive. May be I missed something conclusive that you read to come to your opinion.

 

[AHTex]

Thank you guys for all the comments! This 4runner has been in the family since about 15,000 miles, but I couldn't gather any info as to service of the transmission, hence the question. I think ill take the risk of a drain and refill and see what happens, and then continue to do that at an interval. I picked up some valvoline maxlife as a replacement. On a side note, Tim thanks for all your videos! They have really helped me out along the rehab process. Ive always taken a methodical/ by the book approach and its clear you do as well. Keep on keepin on and ill post the results!

 

[mtbtim]

I have and what I found was more of opinion, speculation, conjecture and not definitive. May be I missed something conclusive that you read to come to your opinion.

Well, we probably have read a lot of the same stuff, I imagine. Is there anything conclusive, like scientific proof? No, I don't have that. All I know is there have been enough reports of problems after a full flush for a transmission that hasn't seen regular fluid changes that has me believing there is something to this.

Who knows, it could all be BS and conjecture like you say. But, would I exchange out all the fluid on a transmission with an unknown history or a history that shows very long fluid change intervals? No, I wouldn't risk it.

The safer bet is to do the fluid exchange gradually with drain and refills spread out, say every 5k miles. Drain and refills are a dilution process but they will get your fluid in great shape if done regularly enough.

I don't buy into the waiting a certain amount of miles for a full exchange because the life of your ATF directly relates to the temperatures you have been achieving. For anyone who regularly drives in the mountains, waiting 30k or more miles to introduce new fluid is a mistake in my opinion. I think this is the reason most owner's manuals will say a 30k interval for ATF renewal and a 15k renewal if you tow because towing will raise your ATF temps and thus reduce it's effective lubricating life. Anyone who monitors their trans temp knows the temps they're hitting while climbing grades. As the temps go up, the life of your fluid goes down. I like giving my trans some fresh fluid every 10k because I do drive mountain roads quite a bit so the trans temps I'm seeing are much higher than the person who uses their rig as a grocery getter.

Anyway, I think I've beaten this subject to death enough. Everyone should do what they feel is right for their rig.

 

[brillo_76]

I had a 98 with 215k on the clock. When I exchanged the fluid and cleaned the magnets and changed the screen filter.

It now has 260k on it and so far working well.

I did the same thing to a 02 camry with 160k on the clock now it's a 200k.

These transmissions didn't have issues at all. If they did have damage they will fail no matter what.

Essentially, old fluid dosent have any lubrication left and your basically sand blasting your transmission system with all the containments being carried around in the fluid.

Wither you do a quart, gallon or all of it once is up to the owner of the rig. I can see concerns about whether or not to do it.

I do know that they fail if you do nothing. My 1990 Camry failed at 200k miles on it. However everything wears out eventually. So it's up to the owners on what they decide to do and how.

It also seems that the transmission fluid by most owners is never touched. Even the newer transmissions that are supposedly sealed and never needed changed I dont agree with. That fluid gets contaminated just like ours does. So I personally exchange it. But this is me.

Sent from my SM-J337V using Tapatalk

 

[D'arce]

I vé heard of Trans back flush causing issues in transmissions but the myth that old atf keeping your transmission working because of buildup is a fallacy. A damaged transmission on its way out is inevitable. Speculating how many miles before it fails debatable. Good Atf is better at lubricating and heat dissipation which is the key.

I have a Passat TDI that was driving and shifting fine. No quirks and no codes. I changed the fluid (darkish) and around 100 miles later trans took a dump. Coincidence? Possibly. Who knows but I was awful suspicious having just changed the fluids/filter. I made lemonade by swapping to a 5 spd so it worked out in the end. My .02

 

[thezentree]

I would not do a full flush if your fluid is looking dark. At most, I would just a drain and refill exchanging out around 4-4.5 quarts.

The risk your talking about is real. For a trans that has been abused with infrequent fluid changes, excessive wear has occurred. That dirty fluid could be holding suspended friction material that your trans is relying upon to shift properly and not slip. Also, new ATF has excellent detergent qualities. The fresh detergent could act upon sludge build-up in the trans, breaking it free and that sludge could get trapped in fluid pathways, like in the valve body and starve the trans of fluid.

If it's a case where the trans is in bad shape and the clutches are on their last legs, a fluid change could be the end of your transmission because it was relying on that suspended clutch friction material. But, your trans in this scenario was probably close to having major issues anyway and who knows how many more miles you could have gotten out of it.

So, entirely up to you, but if it were me, i'd risk the drain and refill and see how it goes from there. I'd rather know if my trans is on it's last legs because I take long road trips and wouldn't want to get stuck 3 states away from home needing a new transmission.

A friend of mine back home has owned a transmission rebuild shop for decades and has told me almost exactly what you posted.

 

[BoomerBob]

Thank you guys for all the comments! This 4runner has been in the family since about 15,000 miles, but I couldn't gather any info as to service of the transmission, hence the question. I think ill take the risk of a drain and refill and see what happens, and then continue to do that at an interval. I picked up some valvoline maxlife as a replacement. On a side note, Tim thanks for all your videos! They have really helped me out along the rehab process. Ive always taken a methodical/ by the book approach and its clear you do as well. Keep on keepin on and ill post the results!

I think you've got a good plan. Do a drain and fill (about 2.5-4.5 quarts depending on if it's 2wd or 4wd). Even better; drain, drop the pan and replace the filter/screen but a drain and fill will do. In a 1000 miles do it again and again in another 1000 miles. These transmissions hold almost 3 gallons so at most you're only changing 1/3 the fluid at a time.

FWIW, when I bought both my rigs they both had dark trans fluid, but not burnt smelling though. One had 147k and the other 173k. I opted to do the low pressure fluid swap so I replaced all the trans fluid. Both have been great so far. The low pressure pump isn't like the high pressure type they use at a shop which can dislodge particles then clog passages. It flows the fluid in at about the same pressure the transmission circulates it. It's the only safe way to do a complete fluid change. I figured I could always add some Lucas transmission friction modifier if either of them started shifting weird or slipping. I could always do a drain and fill with the old fluid too but thankfully neither was necessary.