Reverse ATF flush?

My ATF on my 2002 pathfinder 3.5 v6 auto 4x4 was starting to look a little brownish at 79k. I was having my oil changed today at the local place that always does it and I asked how much they charged to do an ATF flush. He told me it was $169.99 and I asked them to go ahead and do it- lord knows if I wait till I get around to it, it won't get done.

I asked him what all that included and he said they would unhook my transmission cooler and run it through a machine that would flush out the system. He said it would reverse flush it so that while they didn't change the filter, it would flush it through backwards and basically clean it out anyway. I got to thinking about this and wondered if flowing ATF backwards through the thing is such a great idea. At any rate they did the service and my ATF is nice and bright and red again and I've got the piece of mind of knowing its been flushed, but there is still a lagging doubt about them not doing the filter.

Then again, I know a lot of people that never get the seal seated just quite right after they drop the pan, and they are blessed with everlasting ATF drops on their driveways.

What is your guys opinion of flushing/changing ATF fluid and using a reverse flush system instead of changing the paper filter??

I have heard of problems with flushing. Stuff get dislodged in the process, and causes problems. I'm on the fence. It makes sense, but I've never seen it happen.

A good friend owned a tranny shop in the 80's and 90's. He told me, regarding trans fluid changes, if it's working, leave it alone. I took his advice, and have never had a problem.

i've also heard of ford transmissions that were thought to be bad and all they needed was a fluid/filter change

Well the auto trans in my 2000 suzuki vitara had regular maintenance when my mom owned it but the fluid was good and brown by the time I got it at 180k. I beat the E36 M3 out of it and had about 200k ish on it and took it to a tranny place and asked them about flushing the fluid. The guy pulled out the dipstick, stuck it back in, and said, "son, with 200k on the tranny and the fluid looking like mud, the gunk in that transmission is probably all thats left in there sealing it up. You go and flush that outta there, youre liable to make it 10 miles down the road and have it lock up on you. If I were you, I wouldn't touch it. Just drive it till it goes and consider yourself lucky you got the miles out of that transmission that you have."

I continued to beat on it and tow heavy trailers with it for another 52,000 miles before the transmission finally failed (and bits of metal are stuck to the dipstick). and now used transmissions with warranties are only going for $300 at the salvage yard... so compard to a $150-200 fluid and filter change, I figured for the economy I got out of that one, I was doing alright.

Now the pathy is a different story. I paid a ton of money for it and I continue to pay a ton of money for full coverage on it. I have a great job now but I put over 4000 miles per month on it. Its my daily driver and has to get me through thick and thin, 100 degree days and -10 degree days. I'll pay whatever it takes to keep it reliable... and thus, my quandry.

I understand your concern over reusing the old filter. However, I've yet to see a filter in an automatic that was plugged up from normal use. Only with catastrophic failures do I see junk in the filters.

suprf1y wrote: I have heard of problems with flushing. Stuff get dislodged in the process, and causes problems. I'm on the fence. It makes sense, but I've never seen it happen.

I believe the key here is preventive maintenance. If you do a fluid exchange BEFORE the fluid gets a chance to get all berkeleyed up, (and periodically as the car gets older) it will stay working longer. And yes, the paper filter is really a debris screen. I'm leaving mine alone.

My das has this saying... "If you don't have time to do it right the first time where in hell are you going to find time to do it right the second time"

Wash the underside. get new drain pan. Drop the pan and replace the filter and clean the pan. pour in the new used fluid and be happy knowing you got it right.

Use OEM filter and gasket most OE gaskets are rubber not rubber/cork mix found in cheap aftermarket kits. Ford 4r70w's the gasket is rubber and reusable.

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You can find a place that does not reverse flush. The valvoline I worked at did a flush that used a passive cylinder to exchange the fluid. I.e., the trans moved the fluid in the normal fashion, and it went into a cylinder that was already charged with fresh fluid. As the trans used its pump to push fluid into what it thought was the radiator, the pressure pushed the piston down, forcing in the exact same amount of minty fresh new ATF. There will always be some contaminated fluid still in the system, but youre looking at ~90% new fluid when done, and no threat of backpumping booyah into your trans.

FWIW, we also did change external trans oil filters (mostly subarus) and after working there 3 years, I never once saw one that actually needed changing on any car under 200k miles.

Reminds me I really need to change the ATF in my car, but I'm not looking forward to paying w BMW's extortion price for their special fluid...

I agree about leaving older high mileage trannies alone. I had the fluid changed ony old '92 Olds Cutlass Supreme with only 38k or so on it but most of those were hard granny-drive miles. Made it 2 whole days before the trans failed. I was out of warranty on time but not miles and GM goodwilled half the repair for me because I was calm and rational in discussing it with the service manager, not so for the guy in line in front of me that morning with the exact same problem who screamed and swore at the service guys.

I "repaired" a lot of automatics with just a fluid and filter change.

Maybe someone with more knowledge about auto trans can chime in.

I've heard of guys changing the fluid on an auto trans using this method:

1. unhook both in and out hoses from the trans cooler/radiator.

2. Put the out hose in a 5 gallon bucket.

3. Submerge the in hose in a 5 gallon bucket filled with about 7 qts or so of fresh transmission fluid.

4. Start the car and let it idle - this should pump fluid from the "in" bucket into the trans and pump old fluid into the "out" bucket.

5. Run the car until the trans fluid is fresh and pink going into the "out" bucket.

6. Hook the in and out hoses up to the cooler/radiator.

7. Check the trans fluid level to ensure you have a proper fill.

I haven't tried this method of changing trans fluid but I have heard of backyard mechanics using it. Personally, I wouldn't touch an older and neglected auto trans. I'd follow Andrave's advice. But if I had a newer car or one with a fresh auto trans in it I would use this method to change the fluid and see how it goes.

Xceler8x wrote: Maybe someone with more knowledge about auto trans can chime in. I've heard of guys changing the fluid on an auto trans using this method: 1. unhook both in and out hoses from the trans cooler/radiator. 2. Put the out hose in a 5 gallon bucket. 3. Submerge the in hose in a 5 gallon bucket filled with about 7 qts or so of fresh transmission fluid. 4. Start the car and let it idle - this should pump fluid from the "in" bucket into the trans and pump old fluid into the "out" bucket. 5. Run the car until the trans fluid is fresh and pink going into the "out" bucket. 6. Hook the in and out hoses up to the cooler/radiator. 7. Check the trans fluid level to ensure you have a proper fill. I haven't tried this method of changing trans fluid but I have heard of backyard mechanics using it. Personally, I wouldn't touch an older and neglected auto trans. I'd follow Andrave's advice. But if I had a newer car or one with a fresh auto trans in it I would use this method to change the fluid and see how it goes.

This is exactly how I did my Tundra... dropping the pan only frees up 4.5qts but the whole trans + torque converter hold 13. If you really want to change it all you drop the pan, clean, replace filter.... top up and then flush the whole thing that way.

Yup thats how to do it.

I think the manufactures change intervals have little to do with longevity of the no longer their vehicles. I change atf at 20k or so, add a filter to the circuit that changes at 20k as well, and add a secondary cooler after the radiator on the circuit. I like the change method described above as well.

walterj wrote:

Xceler8x wrote: Maybe someone with more knowledge about auto trans can chime in. I've heard of guys changing the fluid on an auto trans using this method: 1. unhook both in and out hoses from the trans cooler/radiator. 2. Put the out hose in a 5 gallon bucket. 3. Submerge the in hose in a 5 gallon bucket filled with about 7 qts or so of fresh transmission fluid. 4. Start the car and let it idle - this should pump fluid from the "in" bucket into the trans and pump old fluid into the "out" bucket. 5. Run the car until the trans fluid is fresh and pink going into the "out" bucket. 6. Hook the in and out hoses up to the cooler/radiator. 7. Check the trans fluid level to ensure you have a proper fill. I haven't tried this method of changing trans fluid but I have heard of backyard mechanics using it. Personally, I wouldn't touch an older and neglected auto trans. I'd follow Andrave's advice. But if I had a newer car or one with a fresh auto trans in it I would use this method to change the fluid and see how it goes.

This is exactly how I did my Tundra... dropping the pan only frees up 4.5qts but the whole trans + torque converter hold 13. If you really want to change it all you drop the pan, clean, replace filter.... top up and then flush the whole thing that way.

Essentially the same as what I posted about valvoline...Minus the fancy pants clear acrylic Piston and QR fittings...and C note pricetag

That's basically how I did my Liberty.

lately some TRUTHFUL trans shops have been sayin(if everything is OK) dont change or touch the trans fluid if the miles are closin on 100K, upsets the whole trans. friction coeficiants and seals..

from new of course if you change every 20-30K, you might be OK some cars have original fluid (my Mitsu. mirage) 100K. added a trans fluid conditioner about 1yr ago, no probs. so im drivin till it goes out

Some clarification might be needed...

Usually "reverse flush" refers to COOLANT maintenance, where scale can build up in layers in the cooling system and reversing the stream dislodges them better.

In the methods described above and/or the equipment used by many repair shops, the transmission pump is used to expel the old fluid and draw in the new...whatever form that might take...but the fluid takes the same path as in normal operation.

I've heard that the AT pump works with the trans in neutral. In park it only circulates in the torque converter. Learned this when I was living in Fairbanks Alaska. I did figure out that it must be right because I warmed my truck up both ways (neutral and park) and the trans was warmer using neutral. Of course that may not work on some newer cars with the safety controls. I did this in the eighties with a 81 K5 blazer.

My 95 F150 needs a trans oil change, I just might try the above mentioned procedure. Last trans change was at ~80,000 miles and it now has 202,000 on it. Figure it might help the mpg - couldn't hurt.

Does the two bucket method really work? Since the fluid is pushed through the cooler by the pump, I wouldn't think it would be able to pull the new fluid out of the 2nd bucket.