Is it safe to use Seafoam Transmission Cleaner on a 222,500 transmission with an unknown service history?


Background
My tranny fluid was pretty gross. Brown-black in color and giving me somewhat hard shifts on the interstate. I've only given it a couple top-offs since buying the car in January 2010 - probably less than a quart total.
I figured it was finally time to flush it.

I bought the IPD flush kit as well as a can of Seafoam transmission conditioner. ...and then I read the warning about flushing grungy fluid wrecking the gearbox. IPD has a warning on the kit and MVS has a lot of warnings about the entire enterprise - sometimes recommending that one leave the old fluid in...

I opted to drain the 3 1/2 to 4 quarts of fluid from the gearbox and refill. According to one set of instructions, doing this multiple times will eventually give me a full flush...

I prepped for the drain and fill by driving the car at operating temp, and driving for a bit in the three forward gears plus a few reverse. I let it cool off, and then removed the gearbox drain plug.

Almost a gallon of extremely nasty warm brown-black fluid poured from the transmission. This stuff had a tinge almost like old boiled brake fluid. I didn't see any floaters, but I did remove a fair amount of magnetic gunk from the transmission plug.

I was quite worried that my gearbox was going to die. But, after refilling it with Valvoline Dex/Merc, I took it for a drive and was amazed at the smooth shifts and generally improved feel. It's crazy how much better the car is moving.

So... given all this, should I use the Seafoam?

Seafoam is a pretty good product, but I question if you really need it. Doing the 'dump' method is find for getting all of the garbage out of the bottom of the sump. I find that a careful flush afterward is better for the internal parts.

The wives tale about flushing an old tranny is a bunch of garbage. So long as you don't use a high pressure flushing machine, all will be good. Using the car's pump to flush the tranny doesn't force any caked gunk through the channels, which the Seafoam is supposed to get rid of.

The AW tranny does have a filter inside, not serviceable, and Seafoam could keep that clean. I haven't figured out the purpose of the wire mesh.

The metal you found on the bottom is normal for a car that has never had a flush.

Klaus
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My advice is free, so you got what you paid for...

Thanks Klaus!

you're right there were a lot of specific warnings about the power-flush machines that shops use, but there were a couple posts warning that flushing old fluid even at idle could reveal hidden problems in the clutch packs.

I guess the thinking is that the old gunk could be all that was holding the tranny together. IPD says this is very rare, but I wanted to err on the side of caution.

It does sound a little like the "warped" rotors story...


To me, it sounds like the seafoam is designed specifically to get the old gunk off the clutch packs... so you can see my concern.

If you want to use Seafoam, I suggest having 'clean' ATF first. Yours is probably clean enough now that you poured out the garbage from the sump. No need to have Seafoam try to disolve that crud and spread it around.

Matthews site suggests to dump and then flush. That works for me. Leaving the old crud ATF in the tranny is hogwash, unless you want to eventually replace the tranny.

Klaus
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My advice is free, so you got what you paid for...