6L80 external filter DIY

cossack · December 30, 2017

After changing out ATF in my '15 model truck, with~35k miles, I decided to install an external filter to help better manage all of the debris, shavings, wear particles inside the transmission. There is no way it can be good for precise piece of hydraulic machinery to run fluid that is so contaminated. Cleaning off that magnet inside the pan, one has to wonder if the internal filter is anything more then a rock catcher .The amount of trash that clings to the magnet in just 35k miles is ridiculous. And that is only a ferrous trash, stuff like: aluminum, clutch material, brass and so on that doesn't stick to the magnet, is still suspended in ATF floating about plugging stuff up. I have never seen same mount of crap in engine's oil pan, never. Meaning that engine's oil filter is doing far better job then an internal transmission filter.

Here is what I did.

After looking at what others have done and taking my time thinking this problem over I decided to install filter next to the windshield washer fluid reservoir/tank. This location is very convenient for several reasons: lots of room, filter changes will be easy, I can keep an eye on the leaks, easy to tell if filter and tubing are getting hot (meaning ATF is flowing), very little new plumbing, and I can easily convert it back to stock because of no permanent modifications.

Then I had to figure out for sure witch way fluid flows through the coolers. What got me confused is the fact that manual shows fluid comes out of the top port and goes back in through the bottom. But a member on here did an external filter set up similar to mine and he swore that the flow is in revers direction from what book says. He even started his truck to verify for sure.

FL335i I'm not out to bash you, I'm simply pointing out that your post had me all jacked up and I hope you don't see it as an attack on you.

Here is a link to that post:

So I decided to verify on my own.

Took the thermostat off the transmission housing. Put it up in the vise and ran air through it to see just what the heck is going on. When thermostat housing is cold, air would come in through the top port ( transmission side ) and out of the two bottom ones ( cooler port and transmission port). No air out of the top cooler port. Heated up the thermostat housing and flow changed. Air comes in through the top transmission side port and out the top cooler side port. No air out of the two bottom ports.

I attaches two horrible hand drawings to hopefully help you understand what I'm blabbering on about.

This would also explain why member on here got turned around and thought that book was showing a wrong direction of flow. When transmission is cold and thermostat is closed, taking off one of the cooler lines will make it appear that fluid is moving in the opposite direction from what manual says.

Again, hope my chicken scratch drawings will make sense.

Now with all that out of the way I used Derale 130005 remote filter mounting kit. Fabricated a bracket to hold the filter high enough to fit Fram #3614 size filters and give plenty of room during the filter change. Used 1/8 inch think by 3/4 inch wide piece of hot rolled that Lowe"s sells. If I remember right bottom leg is 6 inches long, vertical is 6 inches tall and housing mounting flange is 2 and 3/4 inches wide. My horrible welds are just that, horrible, but should be ok to hold up that fram. In the words of AvE " Grinder and paint, make me the welder I an't."

Now for pluming I decided to stick with GM original transmission push connect 3/8 inch transmission line. This is an expensive way to go about it because I had to purchase a hydraulic press/dies in order to form 3/8 GM transmission connection. Its a Mastercool 72485 flaring tool set. If you do buy one make sure it has GM transmission line forming die set. There is a cheaper version of this kit # 72475 that does not have a needed die set. Just a heads up.

I used cheap tube bender from Lowe's, holly crap, its difficult to make a proper bend using that POS. Now I know its a poor craftsman that blames his tools, I'm just letting you know to be ready to redo lines several times if you use that style of bender.

Also you will need two (2) 3/8 inch NPT to 3/8 GM transmission line fitting/adapter to go into the filter housing. I used Doorman 800-606, got it on Amazon. Local parts stores sell them too.

Line I bought at Advance auto parts part number #CN-660, worked great. Those are 3/8 inch OD and are 5 feet long. I went through two of them. If you know what you doing one is plenty. Also don't use the thick stainless tubing Amazon sells. It wont form correct in the die. Plus its a major pain to bend using Lowe's bender. Ask me how I know.

In the above picture I took tube number 14 out and hooked up mine as shown.

Keep the old tube just in case.

Started up and what you know, no leaks, great, so far. Let the truck warm up and keep looking over all the new connections, check under the truck where i have been dicking with thermostat, all good. Take off down the road. Temp outside is ~30 degrees, drove for 10 miles, pull over to check on the connections and look for leaks. Everything looks great, however lines are cold and filter is cold too. I figured no big deal sense transmission is only at 135 degrees at this point and thermostat is still closed. It took transmission about 20 miles to come up to ~185 degrees. Drove around for 5 miles after it warmed up to make sure let all the lines fill up, let the fluid circulate and if there is any leaks let them drip to be easier to spot. Pull in the parking lot, open the hood, lines are hot, filter is hot, everything looks dry and thermostat is dry too. Headed back to the house, check it all over again, looks great.

So that is how I did an external filter on 6L80. I'm leaving that orange Fram until next oil change , which is in~3000 miles. Reason for short run is because I want to cut this filter open asap for my own curiosity and didn't want to waste an Fram ultra on such a short run. Then it will be a Fram ultra and probably run it for two years, which is about ~10000 miles on this truck. Will also do cut it open as well.

UPDATE 6-16-2018 44,685 miles on the truck. Filter in use sense 12-30-2018 39,785 miles. 4900 miles exactly. I did an oil change, tire rotations and figured might as well change out the transmission filter just because I really wanted to see how it looked.

Looks like the internal filter is just a rock catcher, look at the size of those particles on the anti drain back valve:

There was a nice build up of small/fine particles all on the inside of the filter body, just like the crap on inside of the transmission pan:

Filter itself looked great and did a fine job. I installed same orange can Fram and will run it until this time next year. I decided not to drop the pan this time because transmission only has 7200 miles sense last fluid change I'll drop the pan next year and we will see how well this set up does. If there is same buildup on the inside of the pan then this is a useless exercise.

If any of you want a specific picture of the filter media let me know. I didn't bother with it because it looked pretty good and I really couldn't see anything out of the ordinary.

Edited June 19, 2018 by cossack

papageoff · December 31, 2017

Looking forward to seeing your results.

Nanotech Environmental · December 31, 2017

Nice job.

This looks to me like it might also be used to facilitate trans oil changes as well, using the passive flush method. Could rig up one of the lines to act as a flush/fill..........

cossack · January 1, 2018

Thanks! yep should make for an easy way to fluid change/flush.

When I did the initial ATF change back in July, I welded in a drain plug, so that ought to make it easier too.

Also, I'll post pictures of that filter cut open. Should be a good indication on how well its doing.

Edited January 1, 2018 by cossack

Grumpy Bear · January 1, 2018

51 minutes ago, cossack said:

I welded in a drain plug, so that ought to make it easier too.

Photo please.

Eddie 70 · January 1, 2018

Nice work! I read FL355 post some time ago and it has been on my list to do the remote filter thing. I just never have done it. I still want to do this mod. I am currently at 95k miles and changing a gallon of fluid every 10K or 15K miles. I changed the filter and as much fluid as I could around 65K.

Also, nice work on the hard lines. They look very good to me.

cossack · January 1, 2018

11 hours ago, Grumpy Bear said:

Photo please.

https://drive.google.com/file/d/1E0_bs_lVr4acbv6YEHjpiFH9kDMVumC7/view?usp=sharing

Here it is, but again, grinder and paint, make me the welder I an't.

I bought a spare pan off of ebay just in case I ever have to put original back in, it was only ~$17 bucks. Then drilled 1/2 inch hole and welded a nut on the out side. This way most, if not all, fluid will drain out when doing a change. I didn't like the no weld kits that require a nut on both sides, wont get most of the fluid out that way. Can't remember what size bolt/nut I used. Also using a copper washer, sense mating surfaces of bolt/nut are not meant to be air tight. Copper gets crushed and forms a very secure and solid seal. Paint is jut some rattle can rust prevention/bed liner stuff I have sitting around. Figured would hide my ugly welds.

Edited January 1, 2018 by cossack

cossack · January 1, 2018

10 hours ago, Eddie 70 said:

Nice work! I read FL355 post some time ago and it has been on my list to do the remote filter thing. I just never have done it. I still want to do this mod. I am currently at 95k miles and changing a gallon of fluid every 10K or 15K miles. I changed the filter and as much fluid as I could around 65K.

Also, nice work on the hard lines. They look very good to me.

Thanks!

Hey it's not to late, would save you from doing all those fluid changes every 15k miles. Honestly there is nothing wrong with what FL355i did other then the fluid flow direction. If I wasn't so ocd I would have went same route mounting on the frame. There is absolutely nothing wrong with doing it that way.

One thing to note is that kit comes with aluminum hose barb adapters they "feel" (key word here) flimsy. If I was to use it as intended, I would get brass adapters.

Edited January 1, 2018 by cossack

Eddie 70 · January 2, 2018

10 hours ago, cossack said:

Thanks!

Hey it's not to late, would save you from doing all those fluid changes every 15k miles. Honestly there is nothing wrong with what FL355i did other then the fluid flow direction. If I wasn't so ocd I would have went same route mounting on the frame. There is absolutely nothing wrong with doing it that way.

One thing to note is that kit comes with aluminum hose barb adapters they "feel" (key word here) flimsy. If I was to use it as intended, I would get brass adapters.

I also like your idea of welding a drain plug on the trans also. To me the problem I ran into is getting the pan out from under the exhaust. The drain plug would make for an ideal situation along with the remote filter. I don't mind drawing a gallon out the dipstick every 15K or 20K miles. I have the parts in my Amazon list to buy.

cossack · January 3, 2018

20 hours ago, Eddie 70 said:

I also like your idea of welding a drain plug on the trans also. To me the problem I ran into is getting the pan out from under the exhaust. The drain plug would make for an ideal situation along with the remote filter. I don't mind drawing a gallon out the dipstick every 15K or 20K miles. I have the parts in my Amazon list to buy.

It's a complete pain the the butt having to deal with exhaust interference. I'm planing on not having to drop that pan again until some time 150k miles or higher now with my set up.

Hey make a post of with lots of pictures when you gets your knocked out.

Edited January 3, 2018 by cossack

Bobaloo22 · January 3, 2018

Great job! Question, could those of us less talented take tube 14 and cut and modify that and use rubber hose to tie into the same filter housing you used or am I asking for trouble? Also I'm thinking of modifying the tstat. I saw where you reverse the insides and the bypass runs fluid straight to the radiator which in turn keeps temps much, much cooler when towing. Am I crazy for thinking about doing this too?

Thanks,

Bob

cossack · January 3, 2018

15 hours ago, Bobaloo22 said:

Great job! Question, could those of us less talented take tube 14 and cut and modify that and use rubber hose to tie into the same filter housing you used or am I asking for trouble? Also I'm thinking of modifying the tstat. I saw where you reverse the insides and the bypass runs fluid straight to the radiator which in turn keeps temps much, much cooler when towing. Am I crazy for thinking about doing this too?

Thanks,

Bob

Thanks!

Yes, you sure can, take that #14 out and use an adapter. Something like this.

https://www.ebay.com/itm/C-AND-R-Racing-Natural-GM-3-8-Quick-Disc-Hose-Barb-Adapter-Fitting-P-N-42-10004/401464852351?hash=item5d792b7f7f:g:yIoAAOSwb3laPoQx:sc:FedExHomeDelivery!42101!US!-1&vxp=mtr

There are cheaper ones on amazon. Search for " 3/8 gm transmission to 3/8 barb adapter"

Because if you just cut the line, with out adding a barb to it, hose will leak. If you use above adapter and regular 3/8 hose you should be good to go. My die set has no way of making a hose barb, otherwise I'd have no problem cranking out a few adapters for you guys.

I didn't do anything to thermostat, my chicken scratch drawings are just to show how it works from factory. I firmly believe that trans needs to operate at or around ~190 degrees. Now if you need additional cooling, might be a good idea to add another radiator, but factory set up seems solid for a 1/2 ton truck.

Bobaloo22 · January 3, 2018

Thanks for the info! I'm not going to worry about the tstat, just read about a lot of guys doing this mod. I pull a 5K trailer and never have had high temps.

Bob

truckguy82 · January 3, 2018

Can confirm trans fluid goes into the driver side of the trans cooler and out the passenger side

I had a failed trans thermostat that just let out a trickle of flow so I'd always feel the lines with my hand while I was diagnosing my issue. Driver side would always be hot, and passenger side would always be cold, which meant the flow through the trans cooler slow enough that it got cooled to ambient temps.

Edited January 3, 2018 by truckguy82

Eddie 70 · January 5, 2018

I got to thinking about the trans temperature and this remote filter. My drive is 40 miles one way. When I get about 2 miles from work, my trans temp is just getting to 170 degrees. If I understand correctly the flow through the remote filter would not happen until this point. I like this idea but think it is a lot of work for two miles of filtering. Am I missing something here?

Thanks guys.

Edited January 5, 2018 by Eddie 70