Installs between the Allison 1000 case and the factory spin-on filter and pulls ferrous wear debris out of the fluid before it reaches the media.
The Magnefine MF-AL-1 is a magnetic pre-filter for Allison transmissions that use a spin-on filter, which includes the Allison 1000 behind the Duramax in Silverado and Sierra HD pickups and the 2000-2500 Series in medium-duty trucks, buses and RVs. It threads onto the filter boss and the factory spin-on filter threads onto it, so every bit of fluid headed for the paper element passes a magnet first. People shopping for it usually want two things: more protection for a transmission that tows hard, and an easy way to see what is going on inside a unit without dropping the pan.
The spin-on control main filter cleans fluid on the pressure side, right before it feeds the valve body and solenoids. Allison already puts a small magnet on the filter attachment tube for this reason, because steel wear particles are the debris that scores valve bores and sticks solenoid valves. The pre-filter adds a much larger magnet inline ahead of the element. It pulls out ferrous material that the media lets through: clutch plate steel, bearing and bushing wear, and fine gear and planetary debris. The paper element still handles the non-magnetic contamination such as friction material and aluminum.
Treat the magnet as a condition report you read at every spin-on service. Allison's own instruction for the factory magnet is to report any metal larger than dust, and the same logic applies here.
A pre-filter does not fix a transmission that is already slipping or setting codes. If the truck has a shift complaint now, diagnose that first; our Allison 1000 valve body testing guide covers the pressure and solenoid checks. Where the pre-filter earns its price is on a healthy or freshly rebuilt unit you want to keep that way, especially on a tow rig, a hot-shot truck or anything with a tune that adds torque.
The listing covers the Allison 1000, 2000, 2100, 2200, 2300, 2400 and 2500 Series in EVS, HS, MH, PTS and RDS configurations, all of which share the spin-on filter mount. On pickups that means the 2001-2019 Chevrolet and GMC 2500/3500 HD Duramax trucks. The body is about 3 x 3 x 2 inches, so the filter assembly will hang roughly 2 inches lower than stock. Look at the space between the filter boss and the crossmember, exhaust and skid plate before installing, especially if you already run a double-deep spin-on filter. It does not fit the 3000/4000 Series, which use internal cartridge filters. If you are unsure, send us your year and VIN, or browse the Allison 1000 parts page.
If the magnet ever shows heavy metal, drop the pan and replace the internal filter with the Allison 1000 filter and pan gasket kit so the debris already in the sump is captured. Service timing for both filters is laid out in our Allison 1000 fluid and filter service guide.
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Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
No. It goes between the transmission and the spin-on filter. You still run a spin-on filter on the end of it and change that filter on schedule.
It is listed for the Allison 1000 and 2000-2500 Series units that use the spin-on filter mount, which covers 2001-2019 Chevrolet and GMC HD Duramax trucks. It adds about 2 inches of length, so check clearance below the filter before installing.
No. The 3000 and 4000 Series use two internal cartridge filters serviced through covers on the bottom of the control module, not a spin-on filter.
Each time the spin-on filter comes off, unthread the pre-filter, wipe the magnet clean and inspect what was on it, then reinstall. It is reusable.
A light gray film is normal. Flakes, slivers or chunks of steel point to clutch, bearing or gear wear inside the unit and are a reason to take a fluid sample and inspect before it gets worse.
No. A 1000/2000 spin-on filter change loses about a pint of fluid. Top up with an Allison-approved TES 668 fluid and set the level hot.
