Used engine flush, now rear main seal leaking.

[OR VietVet]

So, in no scenario at all does all fresh flushed fluid, say that 5 times fast, ever knock out whatever is left of the clutches? In the scenarios I laid out, it would seem then that each vehicle was going to fail within a week or two, whether a flush was done or not. To me, that does not make sense but I ask because this old dog can be taught new tricks.

I don't doubt what you are saying at all. You are the specialist after all. I just want to understand better so I can recommend and warn my customers the correct way.

 

[NickTransmissions]

So, in no scenario at all does all fresh flushed fluid, say that 5 times fast, ever knock out whatever is left of the clutches?

IMO, It's a matter of perception vs reality (the customer's perception vs mechanical and chemical engineering reality).

Key phrase in your above, "what is left of the clutches". In other words, there's basically nothing left so failure was imminent and the timing of the flush coinciding with subsequent failure was coincidental, not causal...So, just using your example, would it be fair to say that the flush caused the problem or simply hastened the failure by maybe one or two drive cycles where the complete and total lack of maintenance or use/abuse did the other 99.99% of the damage and the flush amounted to just wasted money spent on the part of the customer? Of all the flushes you have performed, what percentage of those transmissions failed within one or two drive cycles of your flush service being performed?

If you alluding to pressure-driven forces knocking off clutch material on an otherwise healthy unit, consider this:

A transmission (all sealing elements across all apply circuits) sees between 50-175+ PSI on a continuous basis throughout a given drive cycle over literally hundreds of thousands to millions of drive cycles in a given lifespan (perhaps 100-150k or more miles)...That's 50 PSI across all idle time and up to 175 PSI at stall rpms constantly while on the road driving. Are we saying that 30 minutes or so on a flush machine one time is delivering more wear and tear to that transmission than all of the previous drive cycles combined? Think about it - does that make any sense?

If these machines are truly causing transmissions to fail, wouldn't it happen every single time a flush is conducted? Wouldn't there have been/be countless class action lawsuits brought by consumers over the decades where shops are doing transmission flushes? Would we still see that particular service being performed at all anymore?

Unfortunately, this myth has a lot of meat/staying power to it (almost dogmatic) and numerous shops refuse to provide needed transmission service to customers whose vehicles are over 75k, 100k and need it (they all have varying cut-off thresholds where they won't do it if the vehicle has that many miles or it or more) and the customer has to go elsewhere or without if there's limited service shops in a given area.

My advice to any service tech or rep when it comes to transmissions is to either follow the factory-recommended intervals for fluid changes faithfully or more frequent if the application is beyond the scope of a daily driver (for example, if someone consistently tows or hauls materials/supplies with a vehicle like our Tahoes or Yukons, I recommend increasing the fluid change frequency by 30% or so). If the OEM doesn't publish an official fluid change cadence (i.e. BMW, MB and some other manufacturers) I recommend every 30-35k if using conventional or 50k if using synthetic in a DD application.

All that said, if you have someone come in w/high mileage and wants a flush, query them on any drivability symptoms and check fluid regardless of mileage but especially if they have 125-150+ on their transmission (or they have no idea how many miles) (I figure you have already been doing this for years as a tech) and do your normal checks of the dipstick, fluid condition/level...if you see any hint of colors other than bright red, don't offer the flush as it's a waste of money...Tell them a pan inspection should be done first to see if they have burnt clutch/other signs of wear first. Protects both of you against any misunderstandings and helps diagnose the trans more effectively.

Otherwise, if you do the flush and the trans fails shortly thereafter, they will (of course) blame you (the technician/shop). They won't consider the possibility that their transmission's already decrepit state and subsequent failure was due to lack of maintenance and/or just age. They will blame you simply because you were the last to touch it, thus they perceive you to have caused the failure...This is the real reason why many shops don't do flushes when mileage climbs past a certain amount. Not because flushes themselves cause the failure but because customers simply perceive it as such. Perhaps we as technicians aren't doing enough to educate the customer on transmission maintenance, servicing and the like and thus allowing the myth to perpetuate over time.

My 2.5 cents for what it's worth...

 

[nonickatall]

I want to understand what @nonickatall and @NickTransmissions are saying. Scenario:

I was in and ran shops for 35+ years. I have seen a vehicle come in the shop for a second opinion of a recommended transmission flush for aged and dirty fluid and after a road test it was determined that the auto transmission functioned fine, shifted as it should and after talking to the owner, they said the same and was just in for an engine oil change and the previous shop had presented him with the transmission flush recommendation.

We agreed that the fluid was dirty looking, light brownish color and the owner did not know the last time the fluid and filter had been done. He trusted our shop and the recommendation was bothering him so he asked us to do the filter change and the fluid flush. We did it and within a week, the shifting norms changed and vehicle was back in the shop with even worse looking fluid than when it was originally offered to us the week before.

To be fair, I myself had cautioned the owner of the flush because I had heard, I am not an auto transmission specialist, from transmission friends in the business that doing a flush can at times be a shock to the clutches and cause later problems. This scenario was repeated at least a half dozen times in my career in shops. Each time a pre flush road test was done and each time the owner said the transmission gave them no concern except that they were warned of dirty fluid.

Are you saying that each time the transmission was actually in the middle of failing and the owner and shop tech did not know it or feel it? I just gotta know because I still do work on the side and have done a few transmission services but have not done and will not be doing any flushes here.

Let's go at it logically, what do we have in an automatic transmission, that comes into contact with oil?

We have the clutches, that have a metal side and a friction lining. These carry out the actual shifting processes and wear out due to the brief friction during shifting.

Then of course we have bearings from the shafts, mostly they are needle bearings, or plain bearings, then we have gears from the planet wheels and, in front-wheel drive vehicles, from differentials, that are integrated into the automatic transmissions. And we have the valve block in which usually some pistons or valves work which are controlled by a solenoid or by solenoid valves which actually control the flow of oil to the clutch pistons.

The bearings and the clutches in particular suffer from old oil, because the old oil changes the coefficient of friction of the clutches and the clutches wear out more. That is also why you notice that an automatic transmission shifts hard, when it has old oil.

And the lubrication is reduced, so it's bad for the bearing and pistons in the valve body.

And as I said, the abrasion from the clutches is constantly being pumped through the automatic transmission and ends up in all channels, pistons and so on.

And then you have the seals of the case the pan and additionally axle seals.

What exactly should happen there or how should it be that the old oil protects the gearbox and the new oil destroys it?

From a technical view I don't see any reason. And as I said before, in the engine you have also plain bearings, and seals and axle seals. They are made of the same material like in the automatic transmission, why you should make and oil change of the engine as often as you like and its good for your engine and at the transmission it should be bad to change the oil?

Incidentally, General Motors also stipulates that the transmission should have a transmission oil change, I think every 45,000 miles.

In Germany we have quite funny situations, e.g. BMW who install ZF transmissions says that their transmissions have lifelong oil filling, and if you ask ZF the manufacturer, they say you should change the oil every 60,000 km. BMW does this in Germany, because in Germany the cars are judged by business people, based on the cost per kilometer driven and if such, an oil change is not done or long-life oils are used, which i don't think much of either, then that lowers the costs and leaves the car cost to look good.

I think if you watch the life from a new transmission until the failure on let's say 200,000 miles the situation that in the beginning when the car is in guarantee and regular service, the oil is changed every 45,000 miles that don't lead into damaged transmission, then probably comes situation where the car was spot used was not treated well, probably by a young men made many kick downs didn't change oil and then after a while the people who drive then the car think, now we can make a service. But if your clutches are worn, your unit will fail someday. Probably it's a psychological thing that people have the feeling I did not do a proper service for my car and the drive very carefully and when they make the service, they think now I have guarantee, everything is okay, I can drive normally make kick down or big asseleration.

And that give the transmission the rest...

So in my in my garage experience I didn't have the experience that people have more damaged units when they make an oil change.

And with the best will in the world, I can't think of any technical reasons, why this should be the case.

 

[rockola1971]

Let's go at it logically, what do we have in an automatic transmission, that comes into contact with oil?

We have the clutches, that have a metal side and a friction lining. These carry out the actual shifting processes and wear out due to the brief friction during shifting.

Then of course we have bearings from the shafts, mostly they are needle bearings, or plain bearings, then we have gears from the planet wheels and, in front-wheel drive vehicles, from differentials, that are integrated into the automatic transmissions. And we have the valve block in which usually some pistons or valves work which are controlled by a solenoid or by solenoid valves which actually control the flow of oil to the clutch pistons.

The bearings and the clutches in particular suffer from old oil, because the old oil changes the coefficient of friction of the clutches and the clutches wear out more. That is also why you notice that an automatic transmission shifts hard, when it has old oil.

And the lubrication is reduced, so it's bad for the bearing and pistons in the valve body.

And as I said, the abrasion from the clutches is constantly being pumped through the automatic transmission and ends up in all channels, pistons and so on.

And then you have the seals of the case the pan and additionally axle seals.

What exactly should happen there or how should it be that the old oil protects the gearbox and the new oil destroys it?

From a technical view I don't see any reason. And as I said before, in the engine you have also plain bearings, and seals and axle seals. They are made of the same material like in the automatic transmission, why you should make and oil change of the engine as often as you like and its good for your engine and at the transmission it should be bad to change the oil?

Incidentally, General Motors also stipulates that the transmission should have a transmission oil change, I think every 45,000 miles.

In Germany we have quite funny situations, e.g. BMW who install ZF transmissions says that their transmissions have lifelong oil filling, and if you ask ZF the manufacturer, they say you should change the oil every 60,000 km. BMW does this in Germany, because in Germany the cars are judged by business people, based on the cost per kilometer driven and if such, an oil change is not done or long-life oils are used, which i don't think much of either, then that lowers the costs and leaves the car cost to look good.

I think if you watch the life from a new transmission until the failure on let's say 200,000 miles the situation that in the beginning when the car is in guarantee and regular service, the oil is changed every 45,000 miles that don't lead into damaged transmission, then probably comes situation where the car was spot used was not treated well, probably by a young men made many kick downs didn't change oil and then after a while the people who drive then the car think, now we can make a service. But if your clutches are worn, your unit will fail someday. Probably it's a psychological thing that people have the feeling I did not do a proper service for my car and the drive very carefully and when they make the service, they think now I have guarantee, everything is okay, I can drive normally make kick down or big asseleration.

And that give the transmission the rest...

So in my in my garage experience I didn't have the experience that people have more damaged units when they make an oil change.

And with the best will in the world, I can't think of any technical reasons, why this should be the case.

There a few here that are confusing "flushing" with "oil change". No where in here did I say to NOT change your tranny fluid. I said dont do a FLUSH.

You left out quite a few seals in your case pan and axle seal(?) example. Axle seal on a 4L60E? Are you in FWD world? The SEALS (Not pan GASKET) are internal parts and when they swell, you are done.
A fluid change is drop the fan change the fluid that is in the pan and then the filter.
A flush which can be done quite a few ways but typical is pull a tranny line and hook a machine up that pumps new or much more often filtered used fluid throughout the tranny and converter. A common practice is to use brand new fluid on a freshly rebuilt tranny (it has a warranty). A tranny that is just in for a repair such as replacement front seal or pump replacement will usually get filtered used fluid for top off. Some shops do it right and always use new fluid no matter what. Some dont.

An engine flush is a totally different evolution. You dont flush an engine with new oil. It is flushed with an "engine flush" which is petroleum distillates and other additives. Why do think on just about every label of a engine flush it mentions "conditions seals". How do you think it does that? What is actually happening when the seals are "conditioned"?

 

[Mudsport96]

I actually saw adding brake fluid to engine oil, swell up a rear main seal on a Ford van and get us home from the Lake of the Ozarks. It was pouring out more than I had seen before and I saw the leak slow way down and get us home. Amazed me.

That is an old demo car trick for getting transmission seals to hold up one last time

 

[Mudsport96]

There a few here that are confusing "flushing" with "oil change". No where in here did I say to NOT change your tranny fluid. I said dont do a FLUSH.

You left out quite a few seals in your case pan and axle seal(?) example. Axle seal on a 4L60E? Are you FWD world? The SEALS (Not pan GASKET) are internal parts and when they swell, you are done.
A fluid change is drop the fan change the fluid that is in the pan and then the filter.
A flush which can be done quite a few ways but typical is pull a tranny line and hook a machine up that pumps new or much more often filtered used fluid throughout the tranny and converter. A common practice is to use brand new fluid on a freshly rebuilt tranny (it has a warranty). A tranny that is just in for a repair such as replacement front seal or pump replacement will usually get filtered used fluid for top off. Some shops do it right and always use new fluid no matter what. Some dont.

An engine flush is a totally different evolution. You dont flush an engine with new oil. It is flushed with an "engine flush" which is petroleum distillates and other additives. Why do think on just about every label of a engine flush it mentions "conditions seals". How do you think it does that? What is actually happening when the seals are "conditioned"?

I think some of his post was lost in translation from his native tongue to English, so there is part of what you were seeing.
Im going to assume that the (axle) in question was the term for (shaft) input or output... possibly (crank) as there was also mention of engine. I deal with translated repair manuals at work and i see alot of that.




As for the OP running engine flush, and anyone looking to do so in the future.

YOU SHOULDN'T HAVE

DON'T.

DO NOT.

I had to take the pan off of the 5.3 in the Silverado to do the pump o-ring at 395k miles. It was not horrible as it got fairly well timed oil changes. I received the wrong o-ring so assembly had to wait a day, so i took the pan and related parts to work and ran then through a fresh batch of industrial solvents in the heated pressurized parts cleaner. While the parts "looked" black and dirty, buildup was not horrible. After the cleaning everything looked new, but the filters on the washer did not have any impressive debris captured and the solvent had not changed color significantly.
So, unless you remove a rocker/valve cover to fix the pcv or a leaky gasket and SEE buildup. Dont think that just because of mileage you need to run a flush. You most likely don't.
If you do see stuff in the rocker area, get a shopvac and suck it out that way. Heads tend to be hotter than the rest of the engine so you do get some coking there that you don't necessarily get other places.