Automatic Transmission and Power Steering Filters

Racor
The Racor division of Parker Filtration is legendary in the commercial diesel realm. They offer more fuel and oil filtration products than we have room to tell you about. Some years back, their commercial vehicle grapevine indicated the need for a retrofit high-flow transmission filter product, so they developed one that would fit most automatics, large to small. Among the tests used to vet the product was installing them on a large fleet of ambulances experiencing early transmission failures. In the long-term tests, according to Racor, failures dropped to just about zero, and the ambulance company saved about $230,000 in repairs and maintenance the first year.

The Racor LFS kit comes with an aluminum filter housing, fittings, mounting bracket and a high-flow, high-capacity spin-on filter. An array of ready-made hoses is available separately in assorted lengths and diameters to accommodate most applications. You can also have hoses made locally or plumb the unit in with tubing if you prefer.

The heart of the Racor LFS kit is a synthetic media filter with 234 square inches of media that delivers a 7-micron nominal rating and 10 microns absolute. It flows eight gallons per minute (gpm) in new condition, which makes it large enough for many big commercial applications. A typical light-truck cooler circuit flows no more than three to four gpm, and many are under two gpm. A quick check of the books showed many medium duty truck transmissions flowing six to eight gpm. The Racor filter is also equipped with a bypass. Racor recommends a 30,000-mile service interval in a hard-worked medium duty truck.

Our test rig for the Racor LFS was an '86 F-250HD with a C6 automatic and 137,000 never-torn-down miles. The oil had been changed 3,000 miles previously with synthetic Royal Purple Max ATF. The older, hydraulically-operated C6 uses a screen, so we expected it to be dirty despite the change, but in only 423 miles it dropped the ISO code from 16/13 to 14/11. That's stunning, considering the low mileage interval. Obviously, the filtering threshold for the Racor LFS is pretty high. By the way, we can't think of any reason why the Racor couldn't be installed on a power steering system as well, though we didn't try it.

Notes on Installation and Testing
We eventually installed both units on both trucks to test the ease of installation, but our lubricant analysis was done with only one unit on each truck. We partnered with Blackstone Labs in Fort Wayne, Indiana, to do the contamination analysis on our oil. In a marathon testing session, we were able to watch our rack of oil samples go through the process.

Both units are simple to install, but there are some considerations on where to place the filters. If you are starting with a new truck, the best place to install either filter is in the cooler outlet line from the trans. Debris buildup in the cooler over time is somewhat inevitable, so placing the filter before the cooler(s) prevents that occurrence. If you buy a new truck, get that filter on ASAP for maximum protection.

If your truck is starting out with some miles or you are installing a rebuilt trans, both Racor and Boss recommend putting it on the return line. It's nearly impossible to get all failure debris from the cooler, and nearly impossible to rebuild a trans that ends up totally clean internally. Better trans shops are now installing inline filters with rebuilds.

Conclusion
Both these systems proved that they could take the ATF well below the range Eleftherakis and Khalil concluded was ideal. On top of that, both these systems are affordable, easy to install, simple to service, and could significantly add to the life of the transmission and reduce the number of times the fluid must be changed.

Comparing the two systems is difficult and essentially comes out a draw. The Magnefine is cheaper and simpler to install initially, but the Racor is easier to service down the road. The Racor filter element alone costs about the same as the Magnefine, but has about 5 times the contaminant-holding capacity and could be run over a much longer service interval. We noticed a 5-degree operating temp drop with the Racor due to the extra plumbing. It's a nose-to-nose finish alright, but one your transmission could greatly benefit from.

Filter Glossary
Absolute Micron Rating: The smallest particle size a filter can catch.

Micron: Micrometer, which equals one millionth of a meter, or 0.00003937 of an inch. A human hair is about 70 to 100 microns in diameter. White blood cells are 25 microns. If you have really good eyes, you can see something of about 40-micron size.

Nominal Micron Rating: The size particle a filter can catch 50 percent of on the first pass.