Please explain why replacing burnt xmission fluid can be bad

[SyberTiger]

Specifically, my question is in regards to what many of us have been told. That is,

"If the transmission has not been regularly service with a fluid flush/filter every 25K miles and you let it get to the point where the tranny fluid is old and burnt you don't want to flush it out with new fluid. Putting new fluid can actually make your tranny symptoms/problems even worse".

Can someone give me the specific reason why this is true? What will the new fluid do to cause more problems that old dirty burned fluid won't? Specifically, I would like to know what transmission components would be negatively impacted by new fluid.

 

[fedyfedz]

the new fluid has cleaner stronger detergents that will casue servo bands or clutch pack to fail.

Picture a screw being held on only by old grimy oil, when you replace fluid with new cleaner fluid might break down the connection holding something together.

 

[Dave_H]

SyberTiger, I am not an AT expert at all and I have wondered why people say this as well...I would think you are going to do more damage to all of the other moving parts if you do not get good ATF back in there. There are so many posts here about how important it is to keep your ATF as clean as possible. I would love to hear more opinions from those experienced working on ATs.
FedyFedz, In your experience where Servo bands fail with new ATF, is it because they have warn or degraded to the point where they are no longer doing a good job of grabbing the clutch drum? or a servo piston is not working well? can these bands be tighted in the explorers if they are slipping?

 

[apanello]

Good luck changing it. It would make it so much easier if ford had installed a dipstick

 

[Artbaileyjr]

..... What will the new fluid do to cause more problems that old dirty burned fluid won't? ....

I've been a moderator on another forum for many years and the same question has been debated ad nausium.

There seems to be two schools of thought. One is that changing fluids after prolonged use (meaning a bazillion years) will cause immanent and relatively rapid transmission failure.

The other camp contends that replacing the fluid and filter will benefit and prolong the useful service life of the transmission.

Having picked up my first Explorer a few months ago, I elected to replace the fluid and filter with new, as my transmission was displaying some shift issues. (150,x.. miles) I was told by two transmission shops that they would not do a service, but instead, a complete overhaul was needed.

After reading numerous posts on this board, I decided to roll the dice anyway. I figured that the worst thing that could happen is I would have to have the trans rebuilt anyway.

The pan was dropped and the fluid was the color of used motor oil, but did not have a burnt smell, but it DID have a strong odor. The pan had no sediment in it, which to me, meant that the friction material was mostly still on the bands/clutches.

Just over 6 quarts of Mercon V were needed to replace fluid lost in the "pan drop"; Just about a 50% change of fluid.

The transmission began working better within about 10 miles. the shift issues disappeared within about 100 miles.

Another pan drop took the fluid to roughly 75% new.

I'm now about 3,000 miles down the road and the transmission now shifts perfectly with no slippage. (It actually never had slippage)

I collect/restore Lincolns and currently own 9 running Lincolns and brought 12 back from the dead. (A4OD transmissions - A couple had over 200,000 mi on the clock when I collected them.) I have replaced the fluid in the same manner, usually doing three consecutive fluid replacements. I have had NO ISSUES, but many say that I have dodged a bullet. Perhaps I have.... But had I listened to the other camp, I'd have had a half dozen transmissions rebuilt by now.

I'm a believer in changing fluids first, then making hard repairs if necessary, after I'm convinced that they are actually needed.

Just my experience....

Art

 

[matt0248]

When the fluid is old and dirty AND there is a lot of clutch pack wear, the fluid itself with all the dirt in it has more friction, so it kinds of assists in the clutchs grabbing. When teh fluid is changed out with new clean fluid, the fluid is more "slippery" and COULD cause slippage. I have seen this before on Chrysler (junk) transmissions. It was usually with a transmission that had some shifting issues to begin with also.

 

[SyberTiger]

I was told by two transmission shops that they would not do a service, but instead, a complete overhaul was needed.

That sure sounds familiar! Some may have read my post in another thread about my experience with this. An excerpt follows....

"I like you have great disdain for those local "tranny experts" who are out to screw over uninformed auto owners. I had a bad experience two years ago with a local AAMCO. I took my Explorer over to the local AAMCO to have a complete fluid flush performed. Instead of performing the fluid flush like I asked I was given the complete "scare tactics" scenario. That is, I was told the tranny was on it's last legs and how I was lucky I made it to their shop. They showed me that the tranny pan had three "chucks on metal" in it. From my observation the metal chunks were three pin bearings that appeared to be brand new and unworn as though they threw some pin bearing in the pan to scare me. They said a fluid flush would most likely make things worse so I told them nevermind and close it up and put the old fluid back in. They wanted to rebuild the tranny for about $2500. I was told that I'd probably not make it home from their shop and to call them when I broke down so they could have their tow truck pick me up. Well, that was two years ago, 6 or 7 round trips between Orlando and Atlanta, and 25K miles ago. The tranny is no better or no worse from when I first took it in for them to look at."

I just wanted to change out the fluid and filter to see if there was an improvement before committing to a larger investment in repair or even a rebuild. The experience noted above left such a bad taste in my mouth that I decided to put off any repair to the tranny. As with you, the AAMCO shop owner said he would NOT do a fluid/filter change for me and had his lead henchman use scare tactic to get me to commit to a full rebuild job by their shop. As I said, I told them to put the old fluid back in and button it up. Having read your post and looking back I'm now wondering how much more wear I put on the tranny with old/bad fluid in it. I should have just crawled under there and did the flush myself.

I called a couple of shops yesterday and asked them "the question". Both shops told me that the valve body and and the solenoids could suffer further damage with fresh tranny fluid. This make no sense to me. My personal theory as to fresh tranny fluid making the tranny operate worse is as follows. The old tranny fluid is more viscous with all the particle matter in it. As such it is more difficult for old fluid to leak past the servo piston pin. Fresh clean fluid is more likely to get past that worn servo pin/bore.

 

[SyberTiger]

When the fluid is old and dirty AND there is a lot of clutch pack wear, the fluid itself with all the dirt in it has more friction, so it kinds of assists in the clutchs grabbing. When the fluid is changed out with new clean fluid, the fluid is more "slippery" and COULD cause slippage. I have seen this before on Chrysler (junk) transmissions. It was usually with a transmission that had some shifting issues to begin with also.

This could very well be the case, however, it would seem that the notorious Ford 55R5 tranny problem oftentime rears it's ugly head around the 70K-80K mileage area. With this mileage it would seem unlikely that the clutch pack would be considerably worn for most folks. The fluid is probably quite dirty around 80K miles if if hasn't been changed out before.

I know I didn't specifically ask the question with regard to the 55R5 but this is a 3rd Gen Explorer forum. I appreciate all the answers and theories as well as the counter arguments.

 

[SyberTiger]

I asked a very large transmission remanufacturing company to answer this question. This is the answer I got via email:

"The quick answer is that when a transmission becomes used to running on the thick, old fluid, the seals inside of it adjust to accommodate the dirty fluid. When this fluid is cleaned out and the new, lubricated, thin fluid is put in, typically there will be pressure issues since it is “stretched” from the old fluid.

Does that make sense? Stretched probably isn’t the best word, but it explains what happens to the inside of a transmission."

It would sound like from their answer it has less to do with "detergents" and more to do with the new fluid being, well....more fluid! That is, the new fluid is thinner (no particle matter) and it is more "slippery". Maybe the detergents wash out some of the crud that is helping make a seal such as where the servo piston pin goes through it's bore.

 

[Artbaileyjr]

I am not an automatic transmission guru, but I AM a hydraulics guru. A transmission is a hydraulic device.

My logic is: If the fluid is replaced, particulate (abrasives) are removed and the lubricating qualities are restored. In the case of the servo bore issue, if the servo bore is worn to the extent that more fluid leaks from the worn bore than is needed to properly operate, and apply sufficient pressure to the servo, then it's already too late. The byproduct is a slipping band. I completely understand the logic here, but additional abrasives in the fluid affect ALL the rest of the components within the transmission including substandard operation or failure of the valves.

Transmission fluid is formulated to not only lubricate, but also possesses friction components to aid the bands and clutches. If the particulate in dirty fluid aids in friction, then it stands to reason that a handful of silica sand added to the fluid will help. (Isn't that what was done to the engines in the C4C cars??) This logic doesn't stand up in my mind. If the bands, clutches and servo bores are warn to the point that they won't function properly with fresh fluid, then it's time for a rebuild anyway!

The detergent qualities ARE THERE to keep sludge at a minimum and keep valves clean and working properly. Refreshing the fluid can only help to clean the residual particulate and aid in smooth operation of the valving components, not to mention better lubrication of bearings, bushings, servos and alike.

If thick, particulate ladened fluid, effectively increasing viscosity, is needed, then the end of the useful service life of the transmission is a forgone conclusion and it's time to pull out the wrenches (or checkbook) and refresh the transmission in it's entirety.

I simply can't wrap my head around the statement that "Dirty fluid is an attribute". <shrug>

Art

 

[SyberTiger]

If thick, particulate ladened fluid, effectively increasing viscosity, is needed, then the end of the useful service life of the transmission is a forgone conclusion and it's time to pull out the wrenches (or checkbook) and refresh the transmission in it's entirety.

I think the dilemma is when you or I take our vehicle to AAMCO or whoever and ask them to change out the old fluid/filter but they refuse to and tell you the age old story that new fluid will make the symptoms worse then attempt to scare you into a complete rebuild. The dilemma being that if you "believe" them as be honest then the only appropriate action would be to do the complete rebuild and forgo a smaller fix such as a servo bore fix. I say this because if you "believe" them then doing just the servo bore fix then replacing the fluid with new fluid will lead to other problems. Again, this if you believe the story about how new fluid can be bad unless you do a total rebuild. The problem is that if this isn't true then there are probably thousands upon thousand of Ford Explorer owners who had their tranny rebuilt after only 80K miles which probably did NOT need it.

I find it very hard to believe that, unless abused, the 55R5 series tranny needs a complete rebuild at 80K miles. Where I'm going with this is that my tranny probably just needed a servo bore fix at 80K miles but since AAMCO used scare tactics I passed on a complete rebuild and I also didn't change the fluid like I probably should have thus leading to even more wear and tear. More than two years later I haven't done a thing to my tranny because of all the talk about how new fluid could make things worse. My tranny still operates with it's "issues" just like over two years ago. No better no worse. Again, I'm left to wonder if I should just go ahead and do just the servo bore fix or have it completely rebuilt. I certainly don't want to do a servo bore fix if adding new fluid will cause problems somewhere else.

 

[Artbaileyjr]

I believe that if the fluid were changed more frequently, then the servo bore issue would be a non-issue. 150K service intervals is simply stupid!

I will always err on the side of frequent service. It has never failed me.

Art

 

[turborich]

If your transmission has dark burnt fluid in it then the damage has already been done. DO NOT flush it or it can fail. All of that dark metallic stuff is the friction material that used to be on the clutches. If you flush it you will be removing all of the friction material from the system plus the new fluid may free up stuck junk that may cause a valve to stick causing more issues.

If it were mine I would drop the pan, clean it, replace the filter, re install the pan & refill with Mercon V fluid. If all goes well then after 6 moths or so you could do this again. I have had good success doing this method on transmissions that have been neglected.

Just imagine a fish tank. If you change all of the water at once you can shock & kill the fish. If you only change out two thirds of the water the fish won't go into shock as easily. Same idea.

 

[matt0248]

The simple thing would be to just find someone who is willing to do the work the you REQUESTED. If they don't want you $$ than so be it.