Change transmission fluid or not?

Wrong. I own them and overhaul/modify them. Experience versus theory, the age old conflict.

Why do you think there are so many different types of transmission fluid? Coefficient of friction varies with the formula. For example, type "F" fluid has aggressive friction characteristics while the newer + fluids are the exact opposite. One common problem encountered when using the wrong fluid for the application is lockup clutch chatter; simply changing to a fluid with the correct friction modifiers will eliminate the chatter by making the clutch slip upon application rather than grabbing. Lots of TSB's on this. "So what" you say? This illustrates how friction modifiers are intended to increase clutch slippage in some cases. When a fluid that has had all of its additive package cooked off (including the friction modifiers), replenishing those friction modifiers can cause unwanted slippage. It's a fact, get used to it. John

My Father once had a 1963 Plymouth Valiant, which he bought when it was 5 years old, with 93,000 miles on it. At about 110,000 miles, we decided to change the fluid. The transmission was working fine at the time. About ten days later, the transmission experienced a major leak while driving home from work on the freeway. A rebuilt transmission was installed.

We were left to wonder if the same problem would have occured if the fluid had not been changed. Without knowing the car's history, we could only guess that the fluid had never been changed. In those days, the owner's manual did not specify a change interval for cars in

*regular* service. I am for changing the fluid on a regular basis, but can fully appreciate Joseph's concern.

-Kirk Matheson

Only in your head.

Probably not, but this "major leak" was probably not the result of changing the fluid, per se. It also probably did not fatally damage the transmission -- it sounds like your father was the victim of a less-than-competent and/or less-than-honest mechanic. Transmission fluid changes themselves do not (cannot) cause sudden catastrophic external fluid leaks, and sudden catastrophic loss of automatic transmission fluid does NOT cause the rapid destruction of the transmission as does sudden catastrophic loss of engine oil.

1963 was the last year for the external trans fluid filter P/N 2400124 on Chrysler products. It was clamped to the driver's side engine-to-transmission bracket of your Slant-6 engine, and the transmission fluid lines were threaded into the filter with a male 3/8" IV-flare fitting on the upstream side and a female 3/8" IV-flare fitting on the downstream side. Such is the alignment of the hard lines that it is VERY easy to cross-thread these connections without realizing it.

Assuming no plain old stupid error was made, such as leaving the transmission pan drain plug loose or overly tightening it -- 1963 was also the last year for a factory-installed pan drain, or leaving the torque converter drain plug loose or overly tightening it -- 1977 was the last year for torque converter drains -- then the most likely cause of your sudden serious leak was an improperly connected external trans filter.

It's almost certain your father's car did not require a rebuilt transmission.

Yes, actually, it did. 1964 was the first year transmission fluid was designated a "lifetime" item for vehicles in "regular" service. In 1963, the change interval was still a 3/36 or 2/24 item, depending on whether the vehicle was in "regular" or "severe" service, and this was stated in the owner's manual.

DS

OK, I was just going to watch, but this is getting painfull.

Let me get this straight, some are trying to put forward the assertion that particulate, specifically friction material from a clutch, floating around in transmission fluid, will create friction between clutch plates that have worn smooth???

OK, lets try an experiment. Anyone who believes this is so, should do the following. Attach smooth metal plates to their shoe soles, then sprinkle sand (play sand would be more fun, but I'll let you use sharp sand) in a thin layer on a steel plate. Have a friend spray water on the plate while you run up and try to stop dead on the plate.

I could be mean and tell you to put transmission fluid on, but I won't.

This to me, looks a lot like lubricated ball bearings, but you know better.

Dan

...or entertaining...

That's John's assertion. He takes transmissions apart, "modifies" them and puts them back together, so he's an expert 'n' stuff.

Why do you think there are so many different kinds of water? It's a fact, get used to it. ;-)

DS

Because the odds are BEST that changing the fluid will stop further deterioration and that the transmission will last the longest this way, even though its life may have been shortened already.

Its really blindingly simple:

option one: Continue to run with burnt fluid -> failure is GUARANTEED option two: Change the fluid -> failure is possible.

Which one is the stupid choice? For me its option one. Kinda like saying "Oh crap, I've got cancer! But sometimes people die from general anaesthesia or chemotherapy side-effects, so I won't get it removed or treated."

There's not a ZERO chance you wouldn't die dur> If this is what you believe, what would be the point in wasting money on a

But here's a critical point- to the best of my knowledge not a single type of conventional clutch-and-band or computer-controlled clutch-only automobile automatic transmission on the market depends on a specific fluid type to set the ultimate fully-engaged holding power of the clutch packs. The different fluid types ranging from the extremely grabby "trick shift" versions of Type F all the way through ATF+4 differ ONLY in how they behave during PARTIAL clutch engagement. Once the clutch is fully engaged, they all hold 100% without slipping. That's why I think no matter how "grabby" you make the fluid, if the clutches are going to slip (when fully engaged) with an ATF+4-type fluid they're going to slip with "grabby" fluid too.

3000,000 km with original fluid, i beleive it is "normal" to see discoloration in the fluid, the tranny shift OK and have power (torque), no apparent failure or shifting/slip/noises problems, some have said in the thread that there is no study or serious compilations on the "old fluid vs tranny mileage" relation, where is the study on the "new fluid vs tranny mileage" relation then?

Do you have experiences on old tranny that the fluid have been changed and not failed afterward? Obviously, most here seems to have more experiences on the contrary...

The problem is that nobody here can prove anything, it's all speculation based on other/friends/relative/personal experiences. Are you telling me that the 5 mecanics are BS me because they think that my tranny will fail in a near future anyway and that they dont want to be responsible or deal with it? Or maybe they are just honest with me and they actually beleive that changing the fluid can do more harm than good? If so, they are all morons that dont know a thing about cars??? In that context, you could be the moron that dont know a thing, how can i know? Can i trust you? If yes, i cant trust the other 5 mecanics!!! Ho my god, what i'm gonna do?!?!

nah...seriously, why it is so difficult for you to accept that you could be mistaken and that the "old fluid vs tranny mileage" relation may be true? And, why not?

No hard feelings he!

I can't resist the temptation to be ornery, even though you're basically taking my side :-)

In light of your experiment, why do modern AC locomotives, with the best computer-controlled wheel-slip limiting technology, still have rail-sanders? And why do they turn them on even on DRY rail when maximum tractive effort is needed?

Told you I was ornery, didn't I :-)

You won't find any manufacturer, anywhere, who will back up this belief of yours.

OK, I swear this will be my last contribution to this thread, so let me say it all in one shot....

My first car was a '68 Ford Ranchero, 302, C4 automatic. It had belonged to my dad, and at some point well over 150,000 miles it got to where it would drop out of gear as soon as the engine dropped below 1000 RPM or so. Loads of fun at traffic lights. On Dad's suggestion, I dropped the pan and found the filter screen CLOGGED with clutch debris. Changed the fluid and filter, and the dang thing was still working, not WELL, but still working, when the car fell apart around it 4-5 years later.

When I got my second car (which I still have, now has over 430,000 MILES- not km- on it...) it had been treated according to the "no fluid change needed in normal service" schedule, despite the fact that it was used to tow trailers. At about 145,000 miles, I changed the fluid. I scraped about a half inch of sandy goo out of the pan, and fixed the leaking oil cooler that had allowed antifreeze to get into the transmission forming all the sandy goo. That transmission lasted another two years and 30,000 miles before the front clutch finally gave up from all the silicate grit it had chewed on due to the fluid leak. A 1973 Chrysler A-904.

When I restored my next car, I gave it its first transmission fluid change at about 130,000 miles. No silicate sludge in it, just a lot of the grey "film" that John K. mentioned.The cavity in the top of the accumulator piston had about 1/4 inch of that stuff in it. That transmission ran until over 200,000 miles and ultimately failed because the low/reverse band broke. Near the end, I had a lot of trouble with it not going into forward gears when cold, and I did several fluid changes because it would work better with fresh fluid. Upon tear-down, the problem turned out to be the fact that the rear clutch piston seals were about the texture of un-cooked dry sphagetti from 32 years of use. 1966 Chrysler A-727.

Shall I go on? I have a couple of other less extreme examples.

What I'm telling you is that mechanics get yelled at, taken to small claims court, and wind up having to pay for transmissions when they fail after fluid changes... WHETHER OR NOT the fluid change was the real cause of the failure. If they change the fluid and the transmission fails next week, will you honestly tell me that you wouldn't try to get a new transmission (or at least a discount) out of them? And even if you are reasonable and understand that it was already sick, don't for a MINUTE try to tell me that 10 other people wouldn't take them to small-claims court in a heartbeat! On the other hand, if they tell you "oh no, we won't touch it!" and then it fails, you can't blame them.

I don't blame the mechanics ONE BIT. I blame people who are ignorant of mechanical design, probability theory and/or are overly litigious. The mechanics have to stay in business after all, and sending you away without giving you a chance to pin any blame on them is the safest approach- from a business perspective. I would hope that SOME mechanics (and I've known a few) would explain all this to you and let you decide, but quite honestly that is harder to do when mechanics no longer know their clients personally. And when people will challenge it in court even if they signed a paper beforehand saying that the mechanic wasn't responsible for failures after a fluid change...

I don't mechanic for a living, and I'm not going to touch your transmission. I'm just telling you what I believe to be the straight story. If it were *MY* transmission (not that I would ever go near a GM TH200R4 or TH700R4 :-p) I would certainly take the risk of changing the fluid and filter. I suppose that its entirely possible (especially with a GM TH200R4 or TH700R4) that the pump might be so far gone that it wouldn't be able to re-prime itself after a fluid change. But I'd rather

*know* that in my garage at a time of my own choosing than discover it one night in a bad part of town.

Do you also not change your engine oil? If not, why?

Personally, I'll believe the people who designed the transmission before I believe the mechanics that work on them. Read your owner's manual carefully. It will tell you if you should change the fluid in your transmission. Many cars don't require changing the fluid if you drive your car within a certain "envelope." However, if you read the fine print, most of us drive in a manner that constitutes severe service (short trips, prolonged idling, driving in cold temperatures, dusty consitions, etc.). Many cars DO recommend transmission fluid changes in the severe service schedule. So, my advice is to read your owner's manual, read the fine print, and be honest about how you really drive. Then select the appropriate maintenance schedule and follow it. If it says to periodically change tranny fluid and filter, do it. If it says to never change it, then do that to if you like. Changing the fluid and filter more often than required does no harm at all other than to your wallet. Not changing the fluid when it is recommended can most definitely cause harm to your transmission and your wallet.

Matt

I read the post. I simply don't believe there is even a remote possibility that a fluid change will cause transmission failure.

And I don't care how many people pass on an urban legend, it still doesn't make it true. I have a number of friends and relatives who send me all sorts of urban legends from the net. The volume doesn't correlate to the veracity of the story. Actually, I think there is possibly an inverse correlation. It seems the more wild and false the story, the more email I get on it. Sounds like the same thing at work with transmission shops.... :-)

Matt

Depends on where the leak was. If it was at the pan gasket, then, yes, this IS a case where the oil change was a contributing factor ... but ONLY because the mechanic didn't replace the pan properly! However, that isn't the fault of the fresh fluid or the new filter.

Matt

Because with fresh fluid in place the contaminated fluid, the likelihood of failure drops dramatically. Is this such a hard concept to understand?

For all of you who think that changing tranny fluid is dangerous to an old transmission, do you feel the same way about changing engine oil? If not, why not?

Matt

John??? :-)

Matt

I don't think the mechanics are being dishonest. I suspect they really believe what they are saying. I believe that John really believes what he is saying. I don't think they are morons, either. I think they are simply ignorant. What are you going to do? Read your owner's manual carefully and thoroughly and do what the manufacturer recommends for your driving conditions.

Matt