Fix it
Loose garage door chain
A chain should sit about a quarter to half an inch above the base of the rail at its midpoint. Sagging more than that slaps the rail, jerks the door at the start of travel, and eventually skips a sprocket tooth. It is one of the few adjustments on an opener that is genuinely designed to be made by the owner.
Do this first
Unplug the opener first. The chain tension is set by two nuts on the threaded shaft at the trolley end of the rail.
1 of 2 are yours to fix
What it usually turns out to be
| Cause | How to tell | What happens next | Yours? |
|---|---|---|---|
| Normal stretch | It has crept looser over a year or two and the door jerks as it starts. | Tighten the outer nut against the inner one until the sag is back to a quarter inch. Do not overtighten — a drum-tight chain wears the sprocket. | Yes |
| A worn sprocket | It goes slack again within weeks of adjusting, or there is a rattle and a skip under load. | The drive sprocket or the trolley is worn. On an older opener this is where replacement usually wins on cost. | Call somebody |
What it costs
$129 – $200
For a tune-up and safety inspection. National guide range, checked September 2026 — get it in writing.
Exact price
Want somebody to look at it?
The range above is a guide. Tell us what you need and somebody who works your area will price it properly.
If the door will not move and a car is stuck behind it, do not wait on a form — leave the door where it is and ring somebody. Do not pull on the spring or the cable.
Your details are used to quote this job and nothing else.
Other faults