Warning signs of bad shocks and struts

Here is what the manufacturer documents we checked list as signs worth having inspected:

From FCA US LLC TSB 02-002-25, Shock And Strut Diagnosis And Replacement Guidelines (May 21, 2025); General Motors bulletin 05-03-08-002J, Diagnosis and Replacement of Shock Absorber and Strut Due to Fluid Leak (August 2024); Nissan bulletin NTB99-001F, Strut and Shock Absorber Replacement Guidelines (December 7, 2021); and the 2026 Toyota Sienna Owner's Manual, If you think something is wrong (p. 617), read November 9, 2026.

Uneven tire wear and suspension noises can have other causes, so these signs mean "have it inspected," not "replace the shocks."

Leaking shock or normal seepage?

Shocks and struts are filled with oil, and a little always escapes past the seal. GM's bulletin sorts what a technician sees into four levels:

From General Motors bulletin 05-03-08-002J, Diagnosis and Replacement of Shock Absorber and Strut Due to Fluid Leak (August 2024), published on NHTSA.gov, read November 9, 2026. GM uses similar levels for coil-over shocks and struts, where oil pooling in the spring seat is a leak.

Other makers draw the line the same way. FCA explains that misting is usually shock fluid evaporating from the rod when it is hot and condensing on the body; it is normal because some oil must stay on the rod to lubricate it, and it is more noticeable at higher mileage. Excessive runs and drips are different and are likely caused by damage to the rod or seal. Volkswagen says a slightly dried oil residue at the top does not indicate a leak, while oil residue running down the body may, and says to inspect only when the shock is clean and dry and no other leak nearby could be mistaken for it. Mazda says a thin, dirty-looking oil film that does not reach the spring seat is normal seepage, but oil that reaches or runs past the spring seat (depending on the part) with a wet, dripping surface is a leak that will worsen over time.

Why shock and strut seals fail

Mazda's bulletin explains the difference. Seepage happens because, as the shock compresses and rebounds, the seal's main lip and dust lip wipe most of the oil off the rod and a very small amount gets out past the dust lip; uneven oil film from normal production variation in rods and seals adds to it. Neither requires replacement.

A real leak, Mazda says, comes from rod damage (a dent, etching, rust or a foreign substance on the rod), lip damage or seal deterioration such as abrasion or hardening. Those do require replacing the shock or strut.

From Mazda North American Operations bulletin 02-002/20, Strut / Shock Absorber Replacement Guidelines (January 9, 2020), published on NHTSA.gov, read November 9, 2026.

Noise, resistance and the hand test

Leaks are not the only failure. Nissan's bulletin has technicians compress and extend the strut or shock rod by hand more than four times and confirm that resistance and sound are normal; if there is unusual resistance or sound, the unit should be replaced. Nissan also has technicians touch oil that has spread past the spring seat or more than halfway down the shock: a thick layer with large pieces of dust and debris means replace, a thin layer without debris does not.

These checks are done with the part exposed and are written for trained technicians, not as a driveway test. If you hear clunks or knocks over bumps, have the suspension inspected rather than guessing at the cause.

From Nissan bulletin NTB99-001F, Strut and Shock Absorber Replacement Guidelines (December 7, 2021), published on NHTSA.gov, read November 9, 2026.

Do shocks and struts have to be replaced in pairs?

Not according to the bulletins we checked. FCA says to replace only the defective shock or strut and not to replace any others because one is defective. GM says not to replace shocks as pairs if only one has been found to cause the concern, and Nissan says not to automatically replace both sides when one is leaking.

After a replacement, FCA notes a new shock or strut changes over time and normalizes after a break-in of about 100 miles (160 km), so a small left-to-right difference you notice at first should even out. Nissan's bulletin also mentions that some strut repairs include a toe or alignment check.

From FCA US LLC TSB 02-002-25, Shock And Strut Diagnosis And Replacement Guidelines (May 21, 2025); General Motors bulletin 05-03-08-002J, Diagnosis and Replacement of Shock Absorber and Strut Due to Fluid Leak (August 2024); Nissan bulletin NTB99-001F, Strut and Shock Absorber Replacement Guidelines (December 7, 2021); read November 9, 2026.

What owners can watch for

The 2026 Ram 1500 manual's once-a-month (or before a long trip) checklist includes checking the steering, suspension, chassis components and axle boots, and its maintenance plan includes periodic inspection of the front suspension, tie rod ends and boot seals. The 2026 Toyota Sienna manual says to contact a dealer as soon as possible if you notice strange suspension noises, uneven tire wear, or the vehicle pulling heavily to one side when braking or on a level road.

A quick look at the shocks when the car is clean can tell you a lot, but remember the bulletins' point: a light, dusty film is normal. Drips, wet oil running down the body, noise or a weak, uncontrolled feel are the reasons to book an inspection.

From the 2026 Ram 1500 Owner's Manual (pp. 305-307) and the 2026 Toyota Sienna Owner's Manual (p. 617), read November 9, 2026.

Suspension service at Elgin Auto Sales & Service Center

Seeing oil on a shock or hearing noise over bumps? Schedule service or see our service specials.

Our service department at 1200 E. Chicago St. in Elgin is open Monday to Friday 8 a.m. to 5 p.m. and Saturday 8 a.m. to 4 p.m., and is closed Sunday. Get directions.