Catalytic Converter - Universal

This procedure covers the installation of a universal catalytic converter on a 2007 Ram 3500 with 5.9L Cummins diesel engine, including removal of the factory converter and proper welding or clamping of the replacement unit.

Warnings

Tools required

Parts

• Universal catalytic converter (diesel-rated, 3-4 inch diameter) × 1 — Match inlet/outlet diameter to existing exhaust
• Exhaust adapter pipes or reducers (if needed for diameter matching) × 2 — Based on converter and exhaust pipe size
• Exhaust band clamps or U-bolt clamps × 4 — 3.5-4 inch diameter stainless steel
• High-temperature exhaust sealant × 1 — Rated to 2000°F
• Exhaust pipe section (if cutting and replacing pipe) × 1 — Match OEM diameter, typically 4 inch

Preparation

1. Park vehicle on level surface and allow exhaust system to cool completely (minimum 2 hours after operation)
2. Apply wheel chocks to rear wheels
3. Disconnect negative battery cable to prevent electrical issues during cutting operations
4. Raise front of vehicle with floor jack and support on jack stands rated for vehicle weight, positioned on frame rails
5. Spray all exhaust hangers and mounting points with penetrating oil and allow to soak for 15-20 minutes
6. Locate the factory catalytic converter - on this vehicle it is positioned in the downpipe section between the turbocharger outlet and mid-pipe, approximately under the driver's door area
7. Measure the inlet and outlet pipe diameters of the factory converter to determine universal converter sizing requirements
8. Inspect exhaust system for other damage or rust that should be addressed during this repair

Procedure

1. 1

   Support the exhaust system
   Place an adjustable jack or support stand under the exhaust system near the catalytic converter location to support the weight of the pipes during cutting. Position support to prevent the exhaust from sagging or binding after cuts are made. Do not support at the converter itself as it will be removed.
2. 2

   Mark cutting locations
   Using soapstone or marker, mark cut lines on the exhaust pipe at least 6 inches on either side of the factory catalytic converter. Ensure you have enough straight pipe remaining to accommodate adapter sleeves or weld joints. On the Cummins exhaust, you'll typically cut in the straight sections of pipe before and after the converter body. Make marks completely around the pipe circumference to ensure straight cuts.
3. 3

   Cut out factory catalytic converter
   Using reciprocating saw with metal cutting blade or exhaust pipe cutter, carefully cut through the exhaust pipe at both marked locations. Make cuts as straight as possible perpendicular to the pipe axis. Have a second person support the converter as you complete the second cut to prevent it from falling. Remove the factory catalytic converter and set aside for proper disposal or recycling.
   ⚠Cutting will produce hot metal shavings and sparks. Ensure no flammable materials are nearby and wear appropriate eye protection.
4. 4

   Clean pipe ends
   Use wire brush, die grinder, or angle grinder to thoroughly clean the cut ends of both exhaust pipes. Remove all rust, scale, carbon deposits, and burrs from the inside and outside surfaces. Clean back at least 2 inches from each cut end. If welding, clean to bare metal. If using clamps, ensure surfaces are smooth enough for proper seal.
5. 5

   Measure and prepare universal converter
   Measure the distance between the two cut pipe ends while holding them in proper alignment. Account for the insertion depth of adapter sleeves or the gap needed for welding (typically 1/8 inch). Subtract insertion depths from total gap distance to determine the required length of the universal converter and any connecting pipes. The universal converter should be oriented with flow direction arrow pointing toward the rear of the vehicle. Most universal converters have directional markings.
6. 6

   Test fit universal converter assembly
   Dry fit the universal catalytic converter with any necessary adapter pipes between the cut exhaust pipe ends. Ensure proper alignment and that the converter body will have adequate clearance from the driveshaft, frame rails, and transmission crossmember. The converter should maintain the same approximate position as the factory unit. Check that exhaust hangers will reach mounting points. Make any necessary adjustments to pipe lengths or positioning before final installation.
7. 7

   Install inlet connection
   If welding: Position the inlet side of the converter or adapter pipe with 1/8 inch gap to the forward exhaust pipe. Tack weld in three locations around the circumference, checking alignment after each tack. Complete the weld with continuous bead around entire joint. If clamping: Slide band clamp onto forward pipe, insert adapter sleeve or converter inlet into pipe at least 2 inches deep, apply high-temperature exhaust sealant to joint, slide clamp over joint area and hand-tighten only at this stage.
8. 8

   Install outlet connection
   With inlet side secured or tacked, align the outlet side of the converter to the rear exhaust pipe section. If welding: Maintain 1/8 inch gap, tack weld in place, verify complete system alignment, then complete full circumference weld. If clamping: Install outlet adapter sleeve with sealant, position band clamp, and hand-tighten. Ensure the entire exhaust assembly from turbocharger back is properly aligned without binding or stress points.
9. 9

   Secure exhaust hangers
   Reconnect or install exhaust hangers at all mounting points to properly support the modified exhaust system. Replace any deteriorated rubber isolators. The exhaust should hang evenly with approximately 1 inch clearance from frame, driveshaft, and body components at all points. Adjust hanger positions if needed to eliminate contact points.
10. 10

    Final tighten all connections
    If using clamp installation: Working from front to rear, tighten all exhaust clamps evenly and firmly. For band clamps, tighten until the band begins to deform slightly into the pipe but does not cut through or excessively crush the pipe. For U-bolt clamps, tighten nuts in alternating pattern to the clamp manufacturer's specification. Do not overtighten, as excessive torque will crush the pipe; verify with the specific clamp's rating. Recheck alignment after tightening each clamp.
11. 11

    Inspect welds (if welded installation)
    If welds were made, visually inspect all weld joints for completeness, proper penetration, and absence of gaps or cracks. Welds should show consistent bead appearance around entire circumference. Any suspect welds should be ground out and re-welded before proceeding.

Reassembly

1. Reconnect negative battery cable
2. Remove jack stands and lower vehicle to ground
3. Allow welded joints to cool completely before starting engine (if welding was performed)

Verification

• Start engine and allow to idle. Listen for exhaust leaks at all connection points - a hissing or ticking sound indicates a leak that must be repaired
• Check for visible exhaust smoke or fumes escaping from joints. Apply soapy water solution to connections if needed to identify small leaks
• With engine at operating temperature, verify no exhaust components are contacting the driveshaft, frame, or body. Check for excessive vibration
• Perform a test drive and monitor for any unusual sounds, loss of power, or excessive exhaust smoke that might indicate backpressure issues
• After test drive, re-inspect all clamps and joints for any signs of loosening or leakage. Retighten clamps if necessary
• Monitor engine performance over the next several days. The turbocharger boost pressure should remain normal and EGTs (exhaust gas temperatures) should not increase significantly compared to pre-repair operation

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