You honestly think we recommend standard ATF because we want peoples trainsmissions to fail? That is insulting. I love talking to our customers every day, but no way in hell do I want any of them to call me saying their pride and joy is broke down because one of our transmissions failed. We are all enthusiasts here at RPM and would never want anyone to be sitting on the side lines because our part failed.

We build over 300 4L60e/65e/70e transmissions a year and not a single customer do we recommend synthetic fluid to. We see less than 10 repair transmissions a year and 99% of those are from over heating the transmission. The temperatures these transmissions have seen a synthetic fluid would have done NOTHING to save them. We have put standard ATF down the 1/4 mile at 9.04@160mph in a C5 Z06 time and time again. ALL of our shop cars run standard Dex 3 ATF. O'reilly auto parts brand to be exact.

If you want to put trans fluid in and forget about it for 100,000 miles, then synthetic might be right up your alley. But when your high performance transmission is baked because you over heated it you will be draining the extra money you spent in fancy fluid into the spent oil barrel.

If top site transmission sponsors are telling you that synthetic isn't worth the money doesn't that tell you something?

 

This is always a touchy subject...

It all boils down to money..

Synthetics aren't better when you don't have the money to use them, or you don't want to incur higher expenses to provide them.

People will say 87 octane is the same as 93 and 93 is a waste of money when they only have enough money for 87 octane..

I'm sure dollar store fluid will work fine, doesn't mean it's the best you can get, and I think anyone that says all fluid are equal is either lying or doesn't live in reality.

 

Well all I can say is we offer a two year warranty and me Id rather see the trans stay cool then have expensive fluid in it. While I have no issue with sythetic fluid its hydraulic and will do the job and will stand up to higher heat without breaking down, to me its just extra money if you can afford it and you have a large cooler allready sure get it. But If your making a choice between large cooler and 12 dollar a bottle ATF get the cooler. Also if the expense of the fluid is going to limit your ability to change the fliud and filter regulary I would rather see a once or twice a year fluid and filter change with cheaper fluid than a change every few years or when you start having and issues which is generally when people decide to change it anyway. When its to late.

Also Of note I have torn down many a 150000 mile trans with regular ATF the fluid black as tar but the seals and the clutches look good as new after you rinsed the black off so the regular stuff is not bad in any way.

Reqardless of fluid type if the temps go over 230 for any length of time the seals will begin to harden and the trans life will be decreased considerably. Transmissions are not engines while they do require some lubrication there biggest concerns are maintaining hydraulic presure and keeping seals alive by keeping temps down.

There is actually very little internal friction in a transmission this can be proven by plastic washers that are used in the 4l60e for example in most cases even at very high milage on tear down provided there has been no failure pushing metal through the lube system or loss of lube you will find these washers ussually look like new also.

The trans itself also makes very little heat for instance we can run one on our dyno a very long time with the cooler looped in to out and it takes a very long time to even get the trans warm as long as the the converter is kept locked. The converter the bigger the stall even more so is where the heat comes from. All energy not sent to the wheels (converter slip during stall up and at low speeds unlocked) does not disapear it is turned into heat energy which IMO is the biggest enemy and that heat is not the result of more or less lubrication but is a by product of the converter itself changing unused energy from the engine into heat.

 

If i remember correctly when I got my Yank Converter there was a note in the box advising not to use Synthetic Trans Fulid with their product.

 

There is a lot of truth to that statement. If you can afford a $1500 trans then you can afford an extra $50 for Synthetic.

I would never advocate not using a cooler. Synthetic fluid is not a replacement for using a cooler, obviously. It can tolerate a lot more heat for a lot longer than any conventional. Using a non-synthetic will not cause your trans to fail over night and probably not within 2 years but it will definitely wear out sooner. There is plenty of friction in a trans or they wouldn't get so hot. There is no comparison when you do long term wear test with conventional and synthetic. The synthetic wins by a large margin. You can keep using conventional and it will work fine for several years but if you would have used synthetic you would probably double (and likely, more than that) the life of the trans...strictly from a wear/friction standpoint. You can run a 9 second car on WalMart oils...for a while. The traditional wisdom of oils and change intervals is more tradition than wisdom. Technology has advanced in lubrication (too) not just mechanical/electrical items.

 

Or we can listen to the people who build them...

 

 

Lucas dex 3

 

Experience beats what you've read and heard.

And what about transmission builders recommending conventional fluids to increase wear and rebuild intervals?

What do you expect everything you've read or heard about synthetics to say? Do you think they're going to say it's just as good as conventional but you should use it and use it for longer? Oh boy less mess if you can go double the miles without getting dirty doing fluid changes, just buy the fluid that costs three times more.


Heres one thing I've experienced when I was 13 in the mid 80's. My uncle owned a large rental equipment shop. He became an Amsoil dealer. The Amsoil rep came out with a 3 HP briggs and stratton engine with a plexiglass side cover. He filled it with amsoil, ran it for a few minutes and drained it. He left it at the shop running all day with no oil in it. That was supposed to say amsoil was great or something.

So being a kid, hanging out on summer break in a junkyard full of old broken rental equipment, I got the idea to take the same style 3 hp B&S engine from an old edger in the back, drain the old oil out of it, took it way in the back and bolted it to an old crane. I ran it for two weeks with no oil in it and no pre-treatment. I would fill it with gas all during the day, and at night I'd fill it and leave it running.

Sure it may be an apples to oranges comparison, but thats not something I read anywhere.

 

agreed!

 

I would still disagree that transmissions have alot of friction and that makes them get hot to the contrary locked with a good cooler I have seen trans temps drop to near ambient air temperature in a car and on the dyno locked in a 50 degree room I can tell you from experince it takes forever to heat one up. With a trans the heat producer is the converter and of course all the hot things around it like exhaust and the engine itself.
The fliud argument is as old as the hills my view is get the best you can afford or like and change regularly as keeping the filter clean is actualy even more important to me anyway than the color or fluid condition. Mostly though spend the money to cool the trans the best you can as that will do more than anything to help a trans life long term but like fluid still wont make it take any more power.
There is no magic fluid that will make your trans take even 1 more HP than another anymore than there a magic additive that will fix your trans or make your car fast in the little bottles at the auto parts store (NITROUS OXIDE EXCLUDED) LOL

 

I understand that the converter is the major heat producer but you can't run one without the other and they share the same fluid. I guess maybe I should have referred to it as a Transmission "Assembly" (all parts together).

This is EXACTLY my point...and it is not conventional

 

What I have read and heard ARE people's experiences!!! I am sorry if I haven't had the chance to run a hundred different transmission combinations myself and test everyone. Just because you didn't have the experience/results yourself doesn't mean that it is false.

 

Any fluid is good, as long as it performs all of its functions: lubes, cools, keeps seals/o-rings pliable, provides hydraulic pressure behind pistons, runs hydraulic logic circuits, and cleans...

the last two functions mean you should change fluid/filter often, regardless of synthetic or regular... the fluid is cleaning normal-wear clutch/band material and dumping it in the pan as light/fine sludge, which the filter picks up.

 

One thing not mentioned here is the fluids effect on the co-effiecient of friction of the various clutches and bands in an automatic trans.

Every builder here has the EXPERIENCE of building HUNDREDS of units and seeing the results later down the road.
We also all have a recipe for success that is based on experience (our own by the way)of calibrating a transmission to shift a certain way to quickly apply clutches without hurting hard parts.

If the clutch apply becomes even milliseconds slower due to a lower co-efficient of friction, that equates to more heat at the actual clutch friction and steel. The fluid used DOES affect the apply. This is one reason why I have for years recommended NOT using Type F for my builds.

Frank has given a good reason why the synthetic isn't really needed in an automatic trans. The seals and friction bonding material will be cooked long before even conventional ATF has reached it's failure point.

There are some special instances where I recommend a different fluid but it still isn't synthetic.

Keeping in mind the converter also typically has friction material in it now is another reason why conventional fluid is typically recommended for performance applications where PWM apply is eliminated or greatly reduced.

I recommend the end users go with what their builder recommends, not someone who heard from their brother in law's friend who read an opinion on the internet from a synthetic fluid dealer who said blah,blah, blah...

 

Ok, just trying to understand here ... if synthetic fluid is more slippery = lower coefficient of friction - and Type F is more granular = higher coefficient of friction - then per your argument, the synthetic with lower coefficient should cause clutches to apply with less heat, whereas Type F, with a higher coefficient, would create more heat. In other words, synthetic and Type F are at opposite ends of the spectrum, and should not be conflated.

 

You have it backwards.

Synthetic COULD cause less friction, slowing clutch apply time, creating more heat.

A clutch or band friction under high load needs to apply quickly. It is effectively an oil cooled disc brake.

Think of using synthetic as using a "slippery" brake pad, like some semi-metallics.
It will take more heat but it takes longer to stop, or more apply pressure, or otherwise has to be compensated for.
Whereas an organic pad (Type F) will grab harder but doesn't like heat.

The friction to steel interface point where the "grab" happens in a clutch pack of an automatic trans has to first move the fluid out of the way as it compresses. Think of a hydroplaning effect here. This is why some builders or in some applications a waffled or grooved clutch disc is preferred.

Once it actually makes contact, it has to start to grab. This is here fluid plays a role. Too slippery and the friction "rubs" the steel longer before it matches speed and completely engages.

The friction material has a role here as well because how "spongy" it is determines how much fluid it holds that has to be compressed out of the friction material as it engages. Spongier friction material is good, because it soaks up fluid when not compressed and expels it when it is compressed, which also rids the friction of heat.
This is why many builders use the High Energy material now because it has a very good "sponge" property.

Back to the partially applied "rubbing" mentioned earlier.
This is when the clutch is making heat. Just like a manual trans clutch. If the clutches are trying to apply, but aren't applied, they are making heat.
The heat produced is depending on the power input, the torque load on the output, the speed differential of the frictions vs. the steels, and the pressure applied.

According to some of the automatic transmission design literature out there, the fluid temp at these surfaces on apply can reach 800* F. It's a very small amount of fluid for a very short amount of time, but it gives you an idea of whats happening at the moment of apply.

If you "slip" that clutch longer than intended, the heat develops fast, and kills the frictions, warps or hot spots the steels, or warps the friction backing plate.

I believe this is why for many years the aftermarket continued to use inferior Type F fluid. It is "grabbier" but has lower temp resistance, etc. More likely to varnish.

Dexron II and III is very high quality fluid in non-synthetic form. It has very specific specifications.

I am an advocate of synthetic oils within the engine. There is no real downside to their use there.
In a stock application, the synthetic ATFs give longer service interval (one of the main reasons for their use by OEM's now who are govt mandated to have 100K mike service intervals), give good shift quality for the average vehicle buyer, live under the heat of PWM converter apply, have good extreme cold weather properties, etc. All the properties that the oil manufacturers boast about are true in that application.

However in a performance transmission application where the largest failure mode is burnt or worn clutch material from high HP WOT apply, we like to control the apply time.

Very rarely do we see any significant wear on the metal to metal surfaces of a transmission. The pump bushing is a babbit material very much like a cam bearing in an engine. It has a converter running on it anytime the engine is started. Usually these are in good shape on teardown. The torrington bearings often have no visible wear pattern on the races or rollers after 200K miles.

There is nothing wrong with Dexron III. Again I'm in agreement with all the rest of the PROFESSIONAL builders here. Use Dexron III, use a good cooler, change the fluid and filter more often.

 

We keep a 55 gallon drum of Dex III right next to our dyno for all our transmission testing. I agree with the professional builders here, a combination of regular maintenance, good cooler, and a little common sense works just fine.

Chuck/FLT

 

So, what are the builders thoughts on the new Dex 6?

 

It's a high quality fluid, like any other synthetic. Great for OEM stuff with extended service interval, smooth shifts, PWM converter apply, etc.