Transmission flush good or bad

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Bonnewagon

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This seems to be one of those topics that provokes endless controversy. But I have yet to see evidence against doing this. Not really a flush but a fluid exchange. Open the cooler return line and let the old fluid pump out while re-filling at the dipstick. No solvent introduced. I know on older cars this was a no-brainer but what about the newer electronically controlled units? I have a friend that did an engine/transmission swap without checking the filter as he *ss-u-med it was fine. YUK! Totally filthy. It is a Camaro LT-1 engine into a Malibu but I don't know what trans it is- something from the late 90's. I advised him to do the fluid exchange and he posted it on a Chevy site somewhere and got immediately flamed for even thinking about doing that. What is the harm?
 
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blk7gxn

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This seems to be one of those topics that provokes endless controversy. But I have yet to see evidence against doing this. Not really a flush but a fluid exchange. Open the cooler return line and let the old fluid pump out while re-filling at the dipstick. No solvent introduced. I know on older cars this was a no-brainer but what about the newer electronically controlled units? I have a friend that did an engine/transmission swap without checking the filter as he *ss-u-med it was fine. YUK! Totally filthy. It is a Camaro LT-1 engine into a Malibu but I don't know what trans it is- something from the late 90's. I advised him to do the fluid exchange and he posted it on a Chevy site somewhere and got immediately flamed for even thinking about doing that. What is the harm?
Have been doing this fluid exchange like this for as long as I can remember, my current daily driver has over 320K, ORIGINAL and perfectly shifting miles. The problem occurs with a true "flush machine" when fluid is forced back into the unit under pressure.

I drop the pan, clean, install new filter and gasket, button back up, unhook return line to transmission, fill transmission with fresh clean fluid, run 2 quarts out, shut off, replace 2 quarts, run two quarts out ect ect until fresh bright red NEW fluid comes out of the return line, button everything back up, top off transmission, DONE!
 
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Bonnewagon

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until fresh bright red NEW fluid comes out of the return line, DONE!
Yup, me too. But I have only had T-400's and T-350's my whole life. Now everything is electronically managed. I saw lots of comments like "that stuff you see is not dirt but friction material and needs to stay in there". Yikes! For real?
 

blk7gxn

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Yup, me too. But I have only had T-400's and T-350's my whole life. Now everything is electronically managed. I saw lots of comments like "that stuff you see is not dirt but friction material and needs to stay in there". Yikes! For real?
Your doing it 100% correctly. I do this procedure to my G bodies, right up through my 2004 Grand Prix! The problem with 99% of the lazy *ss critic's out there that HAVE issues, and tell us we need to "keep the grit" in the transmission and not change the fluid out, are the ones who ONLY service their transmissions in the past when they start shifting like crap from never being serviced. When they FINALLY DO service their worn out and toasted transmission at 200K, at that point in time there is no hope, and when they put fresh fluid in, they don't shift BECAUSE the GRIT WAS keeping theirs together, because all their clutches are worn out so badly, the grit is the only thing the transmission is grabbing to move it. For individuals such as us who actually have a brain and service our beloved vehicles PRIOR to problems, there IS NO PROBLEM!

PS...tell your critics that we are supposed to take THEIR advice!?? The same morons who don't do normal service on their vehicles, the same ones who have the problems from their non existent maintenance record, trying to convey us who have NO issues lol...people never fail to amaze me...Stick with what your doing friend! (y)(y):giggle:
 
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oldsofb

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When working at the dealership a lifetime ago, the normal cycle was every 30,000 miles. If you kept to that interval the fluid was good enough that refilling the pan after the filter change was enough for proper maintenance. I never flushed the little bit left in the cooler lines, never. That 30K interval has extended with the advent of synthetic trans fluids, but the principal's the same: stick to the factory recommended service timeframe and all should be well.

Some smaller cars have recommendations to never change the fluid for typical service.

I don't think at any point one could be criticized for doing too good of a job changing out the fluid. The big issue is sticking to the service cycle timeframe.

Any auto trans that isn't serviced until the fluid is a dark dark brown has more issues to deal with than how much of the total fluid is changed out.

Hutch
 
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