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Discussion Starter #1
Quote "The worst thing you can do is change your transmission fluid!" Discussion

Over the years I've heard many people say this. The last two were the Chevy owner across the street and the transmission shop guy.
One thing he said was "That gunky fluid with all the particles in it is making the clutches work"
That makes no sense to me.

Here are two topics:
1. Does the old fluid have properties that are beneficial to the trans?
2. Why gradually change fluid by drain and fill several times with 1000 miles in between instead of just drain and fill several times at once?
 

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Discussion Starter #2
Thank you moderators.

Yes... I realize you've all been through this. I've tangled with a lot of car problems in my day, but the last time I messed with a transmission was 1993. That was a simple service.
If I had a forum like this back then, I would've been able to save myself from the financial needs of the transmission shop.
 

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I'm stealing a response from Click N Clack the Car Talk guys, but this advice is one of those things that grizzled old mechanics THINK they've learned through experience, but actually have learned the WRONG lesson!

For many years, their experience has been with typical car owners who neglect things until something shows signs of distress. So Joe Sixpak drives his car fat dumb and happy and never changes his ATF until with 85k miles on it, it doesn't shift into reverse one morning for about 15 seconds. Finally, something gives and the shift completes. Joe says "Uh oh, better go have the tranny fluid changed." he takes it to the shop, shop changes the ATF. Now the damage is really already done. Joe knows there have been symptoms, but he keeps his mouth shut. Joe gets the car back from the mechanic and 3 weeks later the thing stops shifting. He has it towed back to the shop and starts chewing the poor guy out for "Screwing up my transmission" and wants it fixed for free.

Over time, the mechanic gets sick of this routine or starts to think that it really WAS the new fluid that caused the damage! In reality, it is neglect that caused the damage. It was the early symptoms of failure that prompted the ATF change and the big failure that followed soon after had NOTHING to do with the new ATF.

The only time this MIGHT be true is when/if the fluid has been neglected SO long that goo and varnish are built up everywhere. If you suddenly introduce new high detergent ATF into that environment, great globs and chunks might come off and clog screens and small orifices. The way to avoid this is do do PREVENTIVE ATF changes, not wait until the trans is showing signs of distress.
 

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Manny, I've always liked your posts. Always informative and well-reasoned.

OF
 

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Discussion Starter #5
Wise words.

Thank you.
 

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by that logic, dirty old oil makes your car run better too!
If that were true, race cars would not have their gearbox oil changed every race. New is always better, and changing more often is better than not. According to the Haynes manual I just bought, they recommend tranny fluid change every 30k mi; every 15k if you live in hot or hilly areas. Some people NEVER change their fluid and then wonder why their tranny failed. It is very simple to do yourself too with common tools. Use synthetic fluids, double the heat range and much better wear protection.
 

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For topic 2, the reason to drive in between fluid swaps is that you only get about 3 quarts of fluid changed each time, and if you simply drain and fill four times, you'll end up emptying old fluid once, and new fluid the other 3 times.

If you just run the engine between flushes, its a little better. You probably get significant amounts of old fluid out on the second empty cycle, but not much after that.

There's a PDF around somewhere here that tells how to get the van to shift through ALL the gears while spinning both front wheels so you can avoid the 1000 mile drives in between. I've done it several times, and its not bad at all. By running through the gears and letting the wheels spin, the fluid is fully mixed up and you get lots of the old fluid out. You also have any suspended solids still suspended when you drain the fluid.
 

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SuperDad said:
For topic 2, the reason to drive in between fluid swaps is that you only get about 3 quarts of fluid changed each time, and if you simply drain and fill four times, you'll end up emptying old fluid once, and new fluid the other 3 times.

If you just run the engine between flushes, its a little better. You probably get significant amounts of old fluid out on the second empty cycle, but not much after that.

There's a PDF around somewhere here that tells how to get the van to shift through ALL the gears while spinning both front wheels so you can avoid the 1000 mile drives in between. I've done it several times, and its not bad at all. By running through the gears and letting the wheels spin, the fluid is fully mixed up and you get lots of the old fluid out. You also have any suspended solids still suspended when you drain the fluid.
i just take the van out on the highway to lock up the TC for a few minutes then do another D&F. Can get 4 D&F done in a couple hours. i know if i used the jack stand method the van would jump off and crash into the house (i have bad karma that way ) :stupid:

sometimes i am lazy and will drive the van to work for a week and do another fluid change every week end.
 

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Every machine wears differently. Quality practices have improved the machines, in this case our cars, greatly and to the point that they all will fail similarly. But not identically, because the environment can be so different, especially for a car. Weather, dust, driving style, trip length, min/max temperatures and a lot of other factors will determine exactly WHEN it will fail.

My '99 with 125K miles had nice clean mini-screens on the pipes. I never changed the ATF until just recently, put 15 litres of Valvoline 'Honda compatible' ATF from WallyMart (at $4/L instead of Honda's $9) - based on the advice of this forum - I think it's sound advice with a reasonable price. If it goes - it goes... fix it or replace it... and always have a backup plan!
 

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That 1,000 miles between drain/fills to mix up the fluid has a couple extra zeros on it!

10 miles oughtta give you plenty of mixing new and old fluid.

I dunno if it is true of the Ody or just internet myth, but I once heard that Hondamatics all have an extra mechanism that is engaged when you actually select D1 for extra slip resistance.

So true or not, I run the selector through all the gears several times a year. The more you keep things moving in there, the less crud builds up on immobile parts.

You can always tell if an idea in one of my posts is originally mine or not. If it's a GOOD idea, I stole it from somebody else!
 
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