Replace a carrier roller by securing the machine, removing the track and accessing the top roller, unbolting and lifting the old unit, fitting and torquing the new one, then re-tensioning the track. Confirm the part number and position before starting. This guide covers the carrier roller on the top run, which is matched and torqued separately from the bottom rollers.
Related reading: for identification and size matching, see our carrier roller sizing guide, and for failure symptoms, see our carrier roller diagnosis guide.
Carrier Roller Replacement Guidance from AFT Parts
- Manufacturer: AFT Parts — excavator and loader undercarriage components.
- Scope: Carrier roller replacement procedure and torque
- Fits: CAT, Komatsu, Kubota, Bobcat, Hitachi, and more.
- Application coverage: Quebec construction, utility, municipal work
- Order check: serial number and part number confirmed before dispatch.
Tools and Safety Setup Before You Touch the Track
Gather lifting gear, a track bar or pry bar, tension-release tools, sockets, and the torque values for the roller bolts. Park on level ground, block the machine, and release track tension before working on the undercarriage.
Never work under a track that still holds tension, and keep hands clear of the track path while it is being removed. A carrier roller sits above the track run, so the track must be lowered or removed enough to reach it safely.
Removing the Track and Reaching the Carrier Roller Safely
Release the tensioner and lower or remove the top run of the track to expose the carrier roller. On many machines, the roller can be reached with the track loosened rather than fully removed.
Clean the area around the roller before unbolting, so dirt does not fall into the mounting face. Photograph the position and the old roller before removal, because the part number and orientation are the reference for the replacement.
Unbolting and Lifting the Old Roller Without Damaging the Bracket
Remove the mounting bolts with the correct sockets, and lift the old roller clear with proper equipment. Inspect the mounting face and bracket for cracks, wear, or corrosion before fitting the new roller.
Do not reuse damaged bolts or hardware. The bracket face should be clean and flat, because a dirty or worn face leaves the new roller running crooked.
Fitting and Torquing the New Carrier Roller to the Published Values
Confirm the part number matches the position, fit the new roller onto the mounting face, and torque the bolts to the published values in the manufacturer's sequence. Use a calibrated torque wrench.
Mark the bolts after the initial torque so a visual check confirms none have moved. A carrier roller installed with the correct flange orientation and torque runs true; a forced or misaligned one wears fast.
The checklist below covers the checks that prevent a repeat job.
| Check | Why it matters | What to confirm |
|---|---|---|
| Part number vs position | Wrong flange or mounting fails early | Confirm against the serial number |
| Mounting face clean | A dirty face leaves the roller crooked | Clean bolts, holes, and frame face |
| New hardware | Reused bolts loosen under load | Confirm grade and condition |
| Torque sequence | Even seating across the bolts | Follow the manual order |
Re-Tensioning the Track and Checking the Sag Range
Re-tension the track to the published sag range, rotate the track a full revolution, and re-check sag. The track must ride centred on the carrier roller flanges after the change.
If the track will not reach the sag range or rides crooked, stop and investigate before running the machine. The problem is usually the tensioner, the new roller's alignment, or the track itself.
Post-Installation Inspection: Listen, Re-Torque, and Verify
After installation, run the track and listen for noise from the top run, then re-torque the roller bolts after the first hours of operation. Record the installation hours and the part number in the machine log.
A post-installation check catches the two failures that show up late: a loose bolt and a misaligned roller. Both are visible in the first shift if the machine is checked properly.
How to Confirm the Roller and Position Before You Start
The fitment check belongs before the bolts, not after: confirm the part number, flange style, and position against the machine serial number while the old roller is still on. Photograph the position and the old part number before removal.
A roller with the right dimensions and the wrong position will bolt up and run misaligned. The ten-minute confirmation prevents a job that has to be redone.
What to Check After the First Shift
After the first shift, check the new roller for noise, the track ride for centring, and the bolts for movement. Re-torque the hardware as the manual requires and record the hours.
A roller that runs clean through the first shift is usually a good install. A noise or a moved bolt in the first hours is a signal to investigate before the wear compounds.
Safety note: carrier roller service requires releasing track tension, lifting, and torque work — use the OEM service manual for your model, follow the published values, and have the work performed by qualified personnel.
Before Ordering
- Confirm the part number and position against the machine serial number.
- Ask whether the kit includes new bolts and the published torque values.
- Check the delivery window against your planned maintenance stop.
- Keep the old roller and hardware until the new part fits.
Conclusion
Carrier roller replacement is a sequence: secure, expose, remove, fit, torque, tension, and verify. Confirm the part number and position, clean the mounting face, and re-torque after the first hours. The roller protects the chain, so the installation deserves the same care.
Key Takeaways for Canadian Operators
- Release track tension before working on the top run.
- Photograph the position and part number before removal.
- Clean the mounting face and use the specified bolt grade.
- Torque to published values and mark the bolts.
Questions to Ask Before You Order
- What torque values does my machine publish for carrier roller bolts?
- Does the roller include new mounting hardware?
- Which part numbers and positions does my order cover?
- What re-torque interval applies after the first hours?
Browse Carrier Roller options and the 2668794 CAT roller for your machine.
Frequently Asked Questions
Do I need to remove the track to replace a carrier roller?
Usually the track must be loosened or lowered to access the top roller. On many machines the track can stay on but released from tension.
What torque should carrier roller bolts be set to?
Use the values published for your machine and bolt size with a calibrated torque wrench. Re-torque after the first hours of operation.
Can I reuse the old roller bolts?
No. Use the specified bolt grade and new hardware where the machine requires it. Reused or damaged bolts loosen and fail under load.
Do carrier roller bolts need thread locker?
Follow the OEM service manual for your model. Some manufacturers specify thread locker or new locking hardware; never add it by habit without the manual's direction.
How long does a carrier roller change take?
With the machine prepared and tension released, a single top roller typically takes a few hours for an experienced shop. First-time jobs take longer.