Transmission Flush and Larger Cooler

Buckwheat · April 27, 2017

Hi Folks,

since I hauled the camper and had my Temps spike at 225 for a few seconds I decided to add a much larger cooler. The transmission cooler is about 4 times as larger as the factory cooler, It s a "long" cooler. So Im doing a complete flush, filter change and adding the larger cooler.

While draining the fluid and dropping the pan to replace the filter I noticed the magnet was covered up real good in fine metal...it wasnt large pieces....not even as fine as beach sand...it was as fine as clay or face powder. I wonder how much more life this transmission has left in it?

LOL Im hoping that real fine metal on the pan magnet is a better sign than BB size chunks of metal.

The fluid did not smell burnt, but was no longer pink or light red in color...it was more like a Burgundy wine color or a brownish red.

Anybody want to hazard a guess as to how much more life it has before it craps out?

the fluid and filter has been changed twice but Im pretty sure it was never completely flushed out

Its a 4L80E transmission with 203,000 behind it

Raptordude · April 27, 2017

Does it shift firmly? Does it slip at all?

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Buckwheat · April 27, 2017

Hi Raptor LOL I guess that would help if I added that....lol sorry about that!

Actually it shifts smooths and doesn't slip

O_J_Simpson · April 27, 2017

If you flushed it, about 30 days left before a rebuild is coming your way.

Buckwheat · April 27, 2017

Hi OJ,

Why is that? Should I just slap in a new filter and add the 4-5 quarts I lost? Plus the difference of the lager transmission cooler? I havent flushed it yet.

Why would a flush crap out the transmission...im trying to understand this.

Thanks!

casey.mikl · April 27, 2017

Hi OJ,

Why is that? Should I just slap in a new filter and add the 4-5 quarts I lost? Plus the difference of the lager transmission cooler? I havent flushed it yet.

Why would a flush crap out the transmission...im trying to understand this.

Thanks!

When you flush a high mileage transmission, you pull all the build up of old fluid and stuff out of it. All the old fluid and stuff that's built up over the years and mileage is essentially helping keep it all together. So when you flush it, it pulls all that out and you very well could have issues. Just drain the pan, change the filter, add the cooler and put new fluid in.

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sdeeter19555 · April 27, 2017

When you flush a high mileage transmission, you pull all the build up of old fluid and stuff out of it. All the old fluid and stuff that's built up over the years and mileage is essentially helping keep it all together. So when you flush it, it pulls all that out and you very well could have issues. Just drain the pan, change the filter, add the cooler and put new fluid in.

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This...

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diyer2 · April 27, 2017

When you flush a high mileage transmission, you pull all the build up of old fluid and stuff out of it. All the old fluid and stuff that's built up over the years and mileage is essentially helping keep it all together. So when you flush it, it pulls all that out and you very well could have issues. Just drain the pan, change the filter, add the cooler and put new fluid in.

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Agree

The gook on the magnet is normal, you'll know when it's dying.

casey.mikl · April 27, 2017

Yep, the magnet stuff is normal. Unless there's chunks or large pieces. Don't worry about it. I have to drain and fill with a new filter soon. I only have 90k on my truck. But when I broke my axle and had to get my truck through about a mile of sugar sand in 2wd, I seen trans temp rise to 240.

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sdeeter19555 · April 27, 2017

Yep, the magnet stuff is normal. Unless there's chunks or large pieces. Don't worry about it. I have to drain and fill with a new filter soon. I only have 90k on my truck. But when I broke my axle and had to get my truck through about a mile of sugar sand in 2wd, I seen trans temp rise to 240.

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Running deep sand or snow at slow speeds is a real test on any trans...

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casey.mikl · April 27, 2017

Running deep sand or snow at slow speeds is a real test on any trans...

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Yeah I know. I have a camp and my property is a decent ways back down a sand road. The roads at times are real deep ruts and it's bad. It gets back and will sit for a little to cool before I leave there again. Truck does great. The 37s really help in the sand.

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Buckwheat · April 28, 2017

Hi Folks,

Thanks for all of that info, that is making some sense! I actually had 4 gallon jugs of synthetic fluid ready to go....It looks like I might now only need about 6 quarts. I will take the other stuff back and get some standard Mercon 3 fluid, change the filter and o-ring seal cup, add my cooler....nice weekend project.

I will also be using my old gasket...the one that came with the filter looked a little cheesy-flimsy. I might add a very thin film of red( hi- temp) rtv to both sides of the gasket...but no so much that is may get inside the transmission and create havoc.

That old filter had some of that fine "mud" on the intake screen fabric too

Raptordude · April 28, 2017

Yeah from what I understand, when you flush out a high mileage tranny, it removes all the clutch material that has worn off and is in the fluid. This may sound like a good thing but it's not. The clutch material in the fluid helps the clutches grab each other. When you flush it out, the clutches wear significantly more because they can't grip each other as well, so they slip. If you know the history of your truck and it has had routine flushes at pretty close intervals, you can get away with flushing it. But it's always safer to do just a fluid change, not a flush.

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Chris · April 28, 2017

Yeah from what I understand, when you flush out a high mileage tranny, it removes all the clutch material that has worn off and is in the fluid. This may sound like a good thing but it's not. The clutch material in the fluid helps the clutches grab each other. When you flush it out, the clutches wear significantly more because they can't grip each other as well, so they slip. If you know the history of your truck and it has had routine flushes at pretty close intervals, you can get away with flushing it. But it's always safer to do just a fluid change, not a flush.

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Here are your clutches on a flush

Not really. These were 9 months old. But my transmission before that had 2 flushes and lasted a year

Raptordude · April 29, 2017

That's odd. My truck had a flush at 50k and a flush at 100k. Currently at 116k and it shifts and pulls like it did when it came off the dealer lot in 2001.

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