Urban Legend, Or Common Sense?
First, as regards ATF vs synthetic, I think that some mechanics become confused about the detergent properties of synthetics in general, and tend to assume that leaks have developed from the detergents wearing away build-up that has formed around gaskets. There should be no harm from changing to a synthetic.
I was doing some research on the use (by some people) of ATF as a fuel additive in both gas & diesel engines. During that process, I spoke to several transmission shops and even a refiner of ATF.
One of the things that came up was what is being discussed now on this thread. Their explanation of the issue was this, if the transmission has been SEVERELY neglected, and not serviced, your fluid will be dark brownish and smell like burnt toast. Once it has been neglected to that certain point, varnish and worn transmission particles will have glazed themselves to the interior parts of the transmission, and it's just a matter of time before the transmission will need to be rebuilt.
Now, it would seem logical that one would immediately want to change that fluid and filter, but from what the experts say, the detergent properties of the old fluid in there is long since worn out. Changing the fluid replaces the old worn out non-detergent fluid with fresh active detergent laden ATF. The ATF will now act as a solvent, wash away the "glaze" and make it a swirling abrasive fluid that will both circulte the harmful deposits, and remove whatever grip was left on the bands from the "glaze", quickly resulting in slippage.
Either way, the trans is headed for the shop, but in this extreme example, changing fluid will actually shorten the length of time until it gets rebuilt/replaced. However, due to the new formulation, Dexron III, transmission shops are seeing less and less of this happening, and a lot of it was older cars that used Type-F. Also be aware that there are additives in ATF that when exposed to rubber, cause the rubber to initially swell, and later disolve into a jelly-like substance...
[Edited by longston on 03-14-2001 at 07:02 PM]
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