28/10/2026
How an excavator track adjuster sets and holds track tension, the parts inside it, the signs of a failing adjuster and what to check before you order a replacement.
The excavator track adjuster is the part that keeps your track at the right tension. When it fails, the track runs loose, comes off, or runs far too tight. This guide explains how a track adjuster works, how tension is set, the signs of a failing adjuster and what to check before you order a replacement.
Key takeaways
A track adjuster fits in the undercarriage frame between a bulkhead and the front idler. Its job is to keep the track correctly tensioned. It does this by pushing the idler forward, away from the sprocket, until the slack in the track is taken up.
You will also see it called a track tensioner, a recoil spring assembly or a tension cylinder. They all describe the same assembly. Most excavators have two, one in each track frame. It works alongside the idler, sprocket and track rollers, so a problem with one of these parts often shows up in the others. For an overview of every part, see our guide to excavator undercarriage parts.
A track adjuster has three main parts. Each one has its own job and its own way of failing.
| Part | What it does | What can go wrong |
|---|---|---|
| Tensioning piston | A grease-filled ram. Pumping grease in pushes the piston out and moves the idler forward. | Piston seals can fail. Grease escapes and the track loses tension. |
| Spring pack | A heavy spring that absorbs impacts when the track hits rocks or debris, then returns the idler to position. | The spring can crack, often unnoticed until the idler is changed. The rod that holds the spring can break, which over-tensions the track. |
| Yoke | A fork-shaped casting that bolts to the idler side-arms or blocks. | The cast yoke can crack under excessive impact. |
Our advice
The spring pack is held under heavy compression. Removing or dismantling a track adjuster is a job for a trained technician with the right tools. Never cut, heat or unbolt the spring assembly on site.
Track tension is set with grease. Pumping grease into the adjuster through its grease fitting extends the piston, which moves the idler forward and tightens the track. Opening the grease valve lets grease out, so the idler can move back and the track loosens.
Tension changes as the track wears. On a steel track, the pins and bushes wear against each other and the chain gets longer. This is called chain stretch. As an example, 1 mm of pin wear plus 1 mm of bush wear on a 50-link chain adds about 100 mm (3.9 in) to the chain length. Adding grease to the adjuster takes up that extra length.
Getting the tension right matters for wear life. A track that is too loose is more likely to come off. A track that is too tight speeds up internal wear in the chain and puts extra load on the idler, rollers and sprocket. Rubber tracks need the same care: our tips to extend rubber track life cover tension checks on compact machines.
Tip
Check the correct track sag figure and measuring method for your machine in its operator's manual. Open the grease valve slowly and carefully. The grease is under high pressure, so keep your face and hands clear of the valve.
A failing adjuster usually shows itself through the track. Look for these signs during the daily walk-around:
If the track jumps, check the other parts as well. Our guides on how to tell if a sprocket is worn and bottom rollers and carrier rollers explain what to look for.
A track adjuster that cannot hold tension should be replaced. Adding more grease to a leaking adjuster only buys a little time, and a loose track is more likely to come off at work.
Look at the idler at the same time. A worn idler can cause a new track adjuster to fail early, and it is far easier to change the adjuster while the idler is already out. If the idler is worn, replace both together. You can find replacement idlers by make, including Case idlers, CAT idlers and Hitachi idlers.
Identify the machine
Note the make, model and serial number from the machine plate. Some models were built with more than one undercarriage, and the serial number helps confirm which one you have.
Confirm the fault
Check whether the track is losing tension, over-tensioned or jumping, and look for leaks and cracks. This tells you whether the adjuster is the cause.
Check the idler
Look for worn treads and flanges, oil leaks and play in the idler. Plan to replace a worn idler with the adjuster.
Check the other side
Most machines have one adjuster in each track frame. If both sides have done the same hours, check the second adjuster too.
Order by machine
Choose the adjuster listed for your make and model, or send us the machine details and we will check the fit.
Our current online range of track adjusters covers the machines below. Each product page shows the quantity per machine and the weight of the assembly.
| Machine | Per machine | Weight each |
|---|---|---|
| CAT 311D, 311D L, CAT 311E, 311E L | 2 | 152.1 lb (69.0 kg) |
| Case CX130, CX130B, CX130C, CX130D | 2 | 112.4 lb (51.0 kg) |
| Case CX135 SR, CX145C SR, CX145C SR LC, CX145D SR LC | 2 | 112.4 lb (51.0 kg) |
| Hitachi EX100-5 | 2 | 115.7 lb (52.5 kg) |
Each adjuster is listed for a named machine. Always order the adjuster listed for your model, and do not assume a part listed for one model fits another. If your machine is not listed, contact us with the make, model and serial number.
The bottom line
Look at the total cost of ownership. A track adjuster that holds tension protects the chain, idler, rollers and sprocket, and keeps the machine working.
Shop parts by machine
A track adjuster is the assembly that sits in the track frame between a bulkhead and the front idler. It pushes the idler forward to set and hold track tension, and its spring pack absorbs impacts from the track. It is also called a track tensioner or recoil spring assembly.
Yes. Track adjuster, track tensioner, recoil spring assembly and tension cylinder are names used for the same part. Some people use "tension cylinder" for the grease ram on its own, which is one part of the full assembly.
Pump grease into the track adjuster through its grease fitting. The grease extends the piston, which moves the idler forward and takes up slack. To loosen the track, open the grease valve slowly and let grease out. Check the correct sag figure for your machine in its operator's manual.
A common cause is grease escaping past failed piston seals inside the track adjuster, so the track loses tension after it has been adjusted. A leaking grease valve or fitting can do the same. Check the adjuster before you keep adding grease.
It is good practice to check the idler whenever the adjuster is replaced. A worn idler can cause a new track adjuster to fail early, and the adjuster is easier to change while the idler is already off.
Most excavators have two, one in each track frame. The track adjusters on our site show the quantity per machine on each product page.
Related guides
Not sure which track adjuster fits your excavator?
Send us the make, model and serial number, and the team will check the track adjuster and idler for your machine.
Talk to the teamGet a quoteManufacturer names and model numbers are used for identification only. Excavator Parts Direct is an independent supplier of aftermarket parts and is not affiliated with any manufacturer named.
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