Inline magnetic 3/8 in ATF filter that splices into a transmission cooler line to catch clutch debris and steel wear particles before they reach the valve body or a fresh rebuild.
The Magnefine 3810000 is a 3/8 inch (10 mm) magnetic inline filter that splices into an automatic transmission cooler line, or a power steering return line, to catch debris the pan filter never sees. People shopping for it have usually just paid for a rebuild, a replacement transmission or a new torque converter and want to protect it, or they have a high-mileage truck with a cooler that may still be holding material from an earlier failure.
An automatic transmission sends hot fluid out to the radiator cooler and any auxiliary cooler, then back into the case, where much of it goes straight to the lube circuit. The pan filter only cleans what the pump draws from the sump, so anything trapped in the cooler or lines comes back into the transmission unfiltered. Transmission Digest has described exactly that failure: a carefully rebuilt unit with a new converter and flushed lines that came back contaminated because debris was still lodged inside the cooler element. An inline filter on the return side is the backstop for that. This unit combines a magnet that the listing rates at about 3 microns for steel particles with pleated media rated at about 25 microns for non-ferrous material, plus a built-in bypass so flow continues if the element loads up or the fluid is cold and thick.
A filter is not a substitute for cleaning the cooler. Flush and backflush the cooler and lines first, or replace the cooler if it has been through a major failure, then add the filter. Our guide to flushing a transmission cooler after a failure covers the procedure, and a can of Lubegard Kooler Kleen cooler flush handles the cleaning step. Measure the outside diameter of the line where you plan to splice in: this filter has 3/8 inch barbed ends, so it suits 3/8 inch hose and steel line connected with short sections of hose. Smaller 5/16 inch systems need a different size.
This is a universal part. It fits any automatic transmission or power steering system that uses 3/8 inch cooler or return line and has a section of hose, or room to add one, where the filter can be clamped in. Heavy-duty trucks with large cooler lines or factory filtration may be better served by a dedicated setup such as the spin-on magnetic pre-filter for the Allison 1000. If you are not sure what line size your vehicle uses, send us the year, model and engine and we will help you check.
Quick-connect cooler fittings come apart more easily with the right tool, such as the OTC 7937 GM cooler line disconnect tool. For more cooler and line parts, see our hard parts category and our article on transmission cooler types and sizing.
| Line size | 3/8 in (0.375 in) barbed inlet and outlet |
| Ferrous filtration | Magnet captures steel/clutch particles to ~3 microns |
| Non-ferrous filtration | Pleated media to ~25 microns |
| Bypass valve | Built in, maintains flow if element loads up |
| Use | Splices into transmission cooler return line; also works for power steering |
The return line, carrying fluid from the cooler back to the transmission, with the FLOW arrow pointing toward the transmission. That placement catches debris the cooler releases before it reaches the case.
No. This is the 3/8 inch (10 mm) version, part 3810000. Measure your line before ordering; a 5/16 inch system needs a smaller filter.
No. Flush and backflush the cooler and lines, or replace the cooler after a major failure, and then add the filter as a backstop. A heavily contaminated cooler can load a small inline filter quickly and push it into bypass.
The pleated element adds some restriction, which is why it has a built-in bypass to keep fluid moving if the element loads up or the fluid is cold. Replace it on schedule so it is not running in bypass.
Yes. The housing is marked for power steering and automatic transmission use. Install it in the 3/8 inch return line to the reservoir with the arrow pointing toward the reservoir.
At your normal transmission fluid service, and earlier after a rebuild when break-in debris is heaviest.
