Robert W. Roe:

As far as the cleanliness of transmission internals go, transmission fluid is an exceptionally good cleaning agent (next time your hands are thoroughly black with greasy crud, try rubbing some transmission fluid on your hands, then wipe them off with a rag -- you'll be amazed).

That being said, there is some accumulation of varnish in certain areas such as the friction materials in bands & clutch packs. This is actually the reason why I used a very brief dosing/exposure of "super sealer/rebuild in a can" in the example I gave in my prior posting in this thread. It wasn't really so much to soften the seals (which in that case was actually a little bonus) -- it was primarily meant to help clean off the varnish accumulation. Those transmission snake oil treatments have some solvents in them, which helps to put any crud into suspension so the filter can take it out. It works as a good "pretreatment" if your transmission is in marginal condition to begin with.

Synthetics in general are EXCEPTIONAL products. I can give you an example: back in the early '80s I was running some showroom stock VW Rabbits & GT 3 Sciroccos in SCCA racing. The front wheel bearings took a tremendous amount of abuse & needed to be replaced fairly often. These bearings are large sealed roller bearings. I disassembled two sets of bearings, cleaned out the stock grease & repacked them with Amsoil synthetic grease. Results: those two cars went for almost an entire season without the need to replace the bearings. Truly amazing if you ask me. Mobile One is phenomenal stuff as well -- if you've ever opened up a high mileage engine that has used it religiously, you'd think that you're working on a brand-new engine! ..Nuff said…

RTH

The synthetic seems to be cleaning my tranny as I drive. Shifting has improved to the point where some of my shifts are perfectly smooth, which I've never had, and I had just changed the ATF with Esso ATF like a year or two ago, probably 15 k mile or so ago.

I'm wondering how soon I should change the fluid and filter again? A year? Less? Opinions?

I'd just like to keep a date in mind considering all the stuff that may have been dissolving out into my new ATF. The post by RunningTooHot does allude to a cleaning, almost flushing, effect.

It did just occur to me, though, that I did add about 2/3 quart in two separate level check/topoffs. I think that this shot of synthetic probably began to clean the seals This allowed molecules of dino and synth to thoroughly intermingle for a while, after which I drained the tranny, changed the filter, and filled it with synthetic. (OK, my shop did it.)

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Bob Roe
Lehigh Valley PA USA
1973 Olds 88, 1972 MB 280SE, 1978 Datsun 280Z, 1971 Ford T-Bird, 1972 Olds 88, 1983 Nissan Sentra, 1985 Sentra, 1973 230.6, 1990 Acura Integra, 1991 Volvo 940GLE wagon, 1983 300SD, 1984 300SD, 1995 Subaru Legacy L wagon, 2002 Mountaineer, 1991 300TE wagon, 2008 Murano, 2007 R320CDI 4Matic 52K, some Hyundai, 2008 BMW 535xi wagon, all gone... currently
2007 Honda Odyssey Touring, 2014 E350 4matic

If it were me, and I'm a guy that overmaintains my vehicles (I won't abide avoidable breakdowns), I'd do another fluid & filter change at 10-15k mi. Thereafter I'd go back to a 30-35k mi per service.

But that's me; FWIW I do happen to have an '88 TE in the garage with 175k on it, and it shifts beautifully on Redline ATF

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"If God had meant for us to walk, why did he give us feet that fit car pedals?" Sir Sterling Moss

Michael
2014 E63S Estate
2006 SLK55
1995 E500
1986 Porsche 944 turbo

That sounds like a pretty good idea. I'd feel better flushing early the first time, just on general principles/why not? I do think the synthetic will loosen up a lot of stuff, so an early ATF change won't hurt.

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Bob Roe
Lehigh Valley PA USA
1973 Olds 88, 1972 MB 280SE, 1978 Datsun 280Z, 1971 Ford T-Bird, 1972 Olds 88, 1983 Nissan Sentra, 1985 Sentra, 1973 230.6, 1990 Acura Integra, 1991 Volvo 940GLE wagon, 1983 300SD, 1984 300SD, 1995 Subaru Legacy L wagon, 2002 Mountaineer, 1991 300TE wagon, 2008 Murano, 2007 R320CDI 4Matic 52K, some Hyundai, 2008 BMW 535xi wagon, all gone... currently
2007 Honda Odyssey Touring, 2014 E350 4matic