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How To Install An External Transmission Filter Kit

This tech article was originally posted at It is primarily intended for Ford trucks but most likely also applies to other Ford models.

As per maintenance I decided as the transmission was starting to show its age, I would install an aftermarket external (remote) transmission filter. From reading on various forums it seemed like a great idea. With added cooling and added fluid, what is there to lose?

If you can change your transmission fluid and do basic automotive electrical work, then this install is quite simple. The hardest part is the planning stage, so take your time, do it once, do it right.

This is for a 1998 Ford F-150 4.2 V6 2 wheel drive with a 4R70W automatic transmission and the towing package, however it would apply to all 4R70W equipped F-150’s (2WD or 4WD), from 1997-2003 and the process would be very similar for 2004-2013 trucks as well.

So, why install an external transmission filter?

Parts Needed

Tools Required

First, open all your boxes up and make a plan on where your going to install the filter, the gauge, etc.

Next, find the transmission outlet and inlet cooler lines coming from the transmission. You can find the outlet line when the truck is warmed up by feel, the outlet will be hotter. Some say use the return line as the temperature will be proof that the coolers are doing their job. I wanted to see the hot side temperature. Make sure you have the filter installed the correct way!

Transmission Filter / Gauge Setup Diagram
Diagram of transmission filter and gauge setup

Locate the appropriate place to mount the filter mount. The easiest place for me was on the main battery fuse cover. I used a piece of stainless steel behind the cover to strengthen it up where the mount bolts in. And I used zip ties to secure the cover to the bracket on the fire wall to prevent the cover from popping off during driving.

Transmission Filter Installation

Install your adaptor fittings using Teflon tape and run your lines. Secure the lines using zip ties, your ladies bra, dogs leash, the screw in wire keepers, whatever. I chose to run them along the length of the radiator shroud.

tranny filter kit hoses

tranny filter kit fittings

Install the sending unit for the temp gauge into the housing if you got the appropriate kit. Make sure your fittings are tight and have Teflon tape on them... they will leak! next wire up the gauge according to the instructions included.

Transmission temperature gauge installed near headliner

Be sure the sending unit is grounded by running a wire from the filter mount to the firewall as you see in the picture below:

Transmission filter kit connections

I did not use Teflon tape on the sending unit at first until I discovered a leak. It is ok to use the tape on the sender because the threads on it will cut through the tape and make a good ground contact.

Crawl under the vehicle and as you will notice the transmission cooler lines have moved do to the addition of the adaptors and now in some places they rub together. Install hose around these lines and zip tie them in place. Granted this may not be a problem...but better safe then sorry.

Fill the filter up with fluid and install the filter on the mount. Start the vehicle up and check for leaks. Top off the fluid as needed. Enjoy your new external transmission filter! I change the filter along with the oil change. each filter change gives me about 12% clean fluid back into the transmission.

Overall it took about three hours to install the kit. This article and associated photos were written and contributed by thefordmaniac, and is used with permission.

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