Allison 1000 Spin-On Magnetic Transmission Pre-Filter

This is the Magnefine MF-AL-1 magnetic pre-filter for Allison spin-on transmission filters. It threads onto the filter boss on the transmission, and the factory spin-on filter then threads onto it, so the assembly sits inline ahead of the paper element. Inside is a magnet that grabs the ferrous wear debris the paper media never catches - clutch plate steel, bearing and bushing material, gear and planetary wear.

Fitment covers the Allison 1000 Series along with the 2000, 2100, 2200, 2300, 2400 and 2500 Series in the EVS, HS, MH, PTS and RDS configurations - the same spin-on filter mount used on Duramax pickups and on medium duty chassis. If your unit takes a spin-on Allison filter, this goes between the case and that filter.

The reason techs run one is diagnostic as much as preventive. On an Allison the pan magnet is buried and checking it means dropping the pan and the internal filters. With a magnetic pre-filter in the loop you pull the spin-on at every service, unthread the pre-filter, and read the debris on the magnet - a light gray fuzz is normal wear, chunks and flakes of steel mean something is coming apart inside and the unit needs to come out before it grenades the pump.

Installation is a filter change. Wipe the mounting surface, oil the pre-filter gasket with clean TranSynd or equivalent Allison approved fluid, hand thread it to the case until the gasket seats, then snug it. Oil the spin-on filter gasket, thread it onto the pre-filter, snug it, run the truck up to temperature and recheck fluid level and the joint for weeping. Clean the magnet each time the filter comes off - it is reusable, not a throwaway.