Change transmission fluid or not?

Take the residue and rub it between your fingers, this matter suspended in the fluid enhances the friction characteristics. Remember the old admonishion to inspect the fluid by withdrawing the dipstick, running it through your fingertips, and inspecting the color, aroma and grittiness? The aroma of burnt fluid is partly due to the additive package having been cooked off. Replacing the old fluid brings in a refreshed additive package that includes friction modifiers and detergents. The friction modifiers can cause the clutches to slip where they didn't before and the renewed detergent can dislodge built up varnish deposits that might migrate to the valves in the valve body and casuse them to bind. John

It doesn't enhance the characteristics. It changes them, but this isn't an enhancement. If the filter is doing its job, the particulates should be in the sub 20 micron size range. If you can feel particles of that size with your fingers, you are a better man than me.

Sure do. It is a good idea to do this reasonably often. However, if you can feel grittiness, then you likely already have serious transmission problems.

If the clutches are so badly worn that new oil make them slip, then they need to be replaced. And the negative affect on other parts such as the oil pump, bearings, etc., from debris in the oil, far offsets any "benefit" to the clutches. I still don't buy the theory that this makes the clutches work better, but even if true, I still wouldn't leave such oil in my transmission. This theory is like saying that blowing the brake dust off of the brake linings on your car will make the brakes less effective. Often such particles serve more of a friction reduction role due to the "ball bearing" affect than anything else.

I don't think dislodging varnish will cause any problem. And transmissions generally don't create much sludge as they don't have the heat and combustion products that afflict the engine. I'm sure you could abuse one enough to cause problems, but you'd really have to work at it.

Matt

Undocumented, unsupportable assertion.

This assertion does not gain veracity regardless of how many times you repeat it.

All wisdom and knowledge will indubitably die with you.

And your "assertions" are "documented and "supported"? Where?

And your opinionated assertions are more veracious than mine? Assertions, both yours and mine, are just that in the absence of documented fact. When you have statistical evidence that the majority of high mileage fluid changes have no ill effect you can prove that my assertions are false, not before. John

Toss theory aside and try it for yourself.

Never denied that. If the trans wasn't already in dire straits the fluid change would have no adverse effects.

Again, no disagreement. But IF a fluid change DOES result in the clutches slipping or other adverse effects, that the fresh lubricant's benefit to the pump, bearings, etc. is moot. The trans is inoperative.

When brake shoes are suspended in oil that analogy is pertinent.

Obviously you have little experience at transmission overhaul. Many unmaintained high mileage units are coated inside with a brown patina of varnish. Considering that valve to valve body clearance is in the neighboorhood of .0005", it doesn't take much to bind up a valve in its bore. John

Yes, because mine agree with *actual* theory of the type followed and understood by engineers, not pretend-theory of the type cooked up by those who let their imaginations pick up where their knowledge leaves off.

I have. I've never felt anything in ATF or engine oil in any vehicle that didn't have a terminal illness. If the particles in the oil are large enough for a human finger to feel, you've already got a serious problem.

And it won't have any adverse effects in any event. It may even help prolong the life until ultimate failure.

I've never seen this happen, never seen it documented in a reliable way, never read a warning from a reliable source (car maker, transmission maker, ATF maker, university research lab, etc.) against changing the fluid in a high mileage transmission that has never had a prior change, and simply don't believe it is true. It doesn't pass the logic test.

Never denied they have varnish. Just said that dislodging varnish won't cause any problems as there isn't enough material to worry about. And

0.0005" is 12.7 microns. You won't find particles even close to that size in a film of varnish. A thick layer of sludge could cause that problem, but you don't get sludge in an automatic typically.

I just did a quick search on transmission filters and they advertise anywhere from 6 micron down to sub-micron capability. Even a filter than catches 10 micron particles will easily handle a tranny with

0.0005" clearances.

Matt

A woman I know never changed her oil for 13,400 miles. The car still ran. Therefore everybody should not change their oil until 13,400 miles. In fact it will cause problems if you change it earlier. I know this because I was there.

Re-read the tread, idiot.

Forget it John, this guy will never be conviced of anything. I've read your posts over the years and know I can trust what you write. As for these other two, that remains to be seen.

Ya know, one thing about this discussion that I am seeing really concerns me a great deal, and it is this idea that a fluid change could ever "not make a difference"

I think most people see John's assertion as a bunch of baloney, insofar that the idea that a trans fluid change (if done with the right fluid) would ever _harm_ a transmission. But what is really insipid is that he is also making an inference that in a trans that isn't high mileage, that it will neither harm or hurt a transmission to change it's fluid. That is a terribly destructive idea, ie: the idea that it's OK to put off maintainence.

In short, John's argument is fundamentally to never change your trans fluid, because the older and more varnished the trans gets, and the more worn out and broken down the fluid gets, the better the fluid is for the trans!

I think that it should be made clear to anyone reading the thread that a trans fluid change if properly done will ALWAYS HELP the trans to last longer!!! If the old fluid was in excellent shape, than the extra lifespan the trans will get may be minor. But, it's ALWAYS going to help it to last longer - assuming it's properly done, and the trans isn't 10 miles away from a complete breakdown already!

Ted

Your opinions are just as misinformed no matter how many times we read the 'tread.' Unlike a fine wine, they don't improve with age.

Pot, kettle, black. That was a good one! Keep telling us tales about the guy you know, and the knowledge you derive from him, it makes for entertaining reading.

Geez, for an engineer your reading comprehension aint worth shit. What an imbecile.

I certainly have, and those particles are an extremely slippery "goo" that feels about like grease. So how can these pulverized particles that are NOT ATTACHED to the clutch plate help it grip the steel plate?

Probably so, at least on a few of the plates. But that still doesn't answer the question of how this alleged free-floating clutch material in the fluid which isn't attached to the clutch disks, helps them grip.

And even if it did, who in their right mind would consider that a "working" transmission?

Don't know how you got that impression, I'm of the opinion that changing one's fluid daily wouldn't be excessive. The subject is not the value of fluid changes per se, but the risk of changes in HIGH MILEAGE units that previously had NO fluid change. Learn to read.

Nice mushrooms? Once again, learn to read.

Show the line where I said that, time and date stamp included.

That's the basis of this argument, if you have absolute proof of that statement, post it. Otherwise yours is just another opinion. John

In the early part of the last century, engineers computed the maximum speed the human body could endure; it was in the neighboorhood of 40 mph. In 1957 engineers computed the minimum elapsed time it would take a wheel driven vehicle to accelerate through the quarter mile, it was in the 8 second range. I could go on. John

Don't get me wrong, I have great respect for John. If you've ever read his posts in alt.hi-po.mopars, its clear he's forgotten more about Mopars than most of us know. We're just disagreeing about our interpretations of the same observations we've both made, and in an area where as far as I know nobody has ever done a serious engineering study to rule out coincidences and establish a clear cause and effect (or lack thereof, as I am arguing). At least from my point of view, there's no disrespect at all.