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Call or Text (352) 722-5295Air filtration on the 1998.5-2002 Ram 5.9L Cummins
From the factory, the 24-valve 5.9L Cummins draws outside air through a sealed airbox fitted with a Fleetguard AF25541 element. Filtered air goes straight to the Holset compressor: an HX35W on 1998.5-1999 and manual trucks, or an HY35W on 2000-2002 automatics. Anything the filter lets through reaches the compressor wheel first. If your truck already wears an aftermarket cold air intake, the filter is part of that kit, and the replacement element comes from the intake maker.
What fails and why
Filters do not break. They load up, or they let dirt by. Poor filtration erodes the compressor wheel blades, and that is the top wear item on the HY35W. The two habits behind it are running a filter long past due and putting too much oil on a reusable filter after cleaning it. The result is boost loss and a dusted compressor wheel.
Stock replacement vs. upgrade
If you want to stay with the factory element, the part number is Fleetguard AF25541. Reusable aftermarket filters pay off over time, but only when you clean and oil them correctly. Either way, the filter you pick matters less than how you keep it. A clean, correctly serviced filter protects the turbo; a neglected one does not.
What we carry
- S&B KF-1000 replacement air filter, listed for 1994-2007 5.9L Cummins.
- S&B KF-1035 replacement filter, listed for 1994-2007 5.9L Cummins and 2001-2010 6.6L Duramax.
- Banks Power 42650 pre-filter wrap for Banks Ram-Air cold air intake filters 42158 and 42188.
- S&B 4-inch silicone coupler with clamps for joining intake tubing.
Fitment notes
Match the filter to the intake on your truck, not just the year. A factory airbox and an aftermarket cold air intake take different elements, and different intake kits use different filters, so read the part number on the filter you are pulling out. The Banks wrap is listed only for the Banks Ram-Air filters above. The S&B filters here are listed back to 1994, so they also cover the earlier 12-valve trucks. Measure the joint before you order the 4-inch coupler. Verify by VIN or call us.
Frequently asked questions
What air filter came on the 1998.5-2002 5.9L Cummins?
A Fleetguard AF25541 in a sealed factory airbox that draws outside air. If you still run the stock airbox, that is the element to replace it with. If you have an aftermarket intake, use the replacement filter made for that kit.
Are reusable air filters worth it on a 24-valve?
They pay off over time, but they put the job of keeping the turbo clean on you. Poor filtration erodes the compressor wheel, and an over-oiled reusable filter is one of the usual ways it happens. Clean it when it needs it and oil it lightly and evenly.
What does the Banks pre-filter wrap do?
The Banks 42650 is an outer wrap that goes over the filter on a Banks Ram-Air cold air intake, for filter part numbers 42158 and 42188. It adds a pre-filter layer in front of the main element. It is listed only for those Banks filters.
How can I tell if dirt got past my filter?
Watch for boost loss, then look at the compressor wheel. A dusted compressor with eroded blades is the sign that filtration failed, and it is the top wear item on the HY35W. Fix the filter problem before you put a new or rebuilt turbo on the truck.
Not sure what fits? Call the shop at the number in the header, or use the fitment checker on any product page. We install everything we sell.