An slipping automatic gearbox is one of the most common complaints with the Volvo S90. Drivers notice rising revs without the car accelerating properly, jerky gear changes, or a slow response when shifting from D to R. Read below to find out what causes the problem and how to tackle it.
Why does the transmission slip in the Volvo S90?
Transmission slip means the gearbox is temporarily not taking the engine’s power properly. The engine revs rise, but the car responds slowly or inconsistently. This happens because the clutch packs or valves in the gearbox are not engaging properly.
The most common causes are:
- Aged or contaminated transmission fluid that has lost its lubricating properties
- Transmission fluid level too low, leaving the gearbox without enough pressure build-up
- Wear to internal components such as the valve body (the valve block that controls gear changes) or solenoids (small electromagnetic valves)
- Faulty seals in the transmission cooler, allowing coolant to enter the gearbox
On the Volvo S90, the model year and engine variant also play a role. Not every S90 uses the same automatic gearbox, so complaints can differ from one version to another. Always check the car’s service history before drawing conclusions about the cause.
Signs of a slipping gearbox
Transmission slip is easy to spot if you know what to look for. The symptoms can be less obvious when driving cold and become clearer once the oil has reached operating temperature.
Common signs include:
- Rev counter rises during acceleration, but the car barely picks up speed
- Jerky or inconsistent gear changes, especially from a cold start
- Slow response when changing driving mode, for example from D to R
- Knocking or grinding noise during gear changes
- Warning message such as “Transmission service required” on the instrument panel
- Dark or burnt smell from the transmission fluid
If you recognise several of these signs at once, an inspection is well worth it. Continuing to drive with persistent slip increases the risk of further gearbox wear.
When should you flush the Volvo S90 automatic gearbox?
Volvo drivers often ask how frequently the transmission fluid should be changed. A commonly used guideline is a fluid change or flush every 60,000 to 80,000 kilometres. For cars that are used more intensively or have been overdue for maintenance for longer, an interval of 60,000 to 120,000 kilometres is a more realistic total range, with interim checks advisable.
Dark or burnt fluid is a sign that the change has been put off for too long. Fresh transmission fluid is usually a clear, reddish colour. If the oil is black or smells burnt, then a flush or drain-and-fill (where the old oil is fully drained and replaced) is the first logical step.
Owners of used S90s with an incomplete service history are at greater risk of transmission problems. It is particularly sensible in those cars to have the fluid checked sooner than the recommended interval suggests.
Fixing a slipping gearbox in the Volvo S90
The approach depends on how severe the problem is and on the condition of the transmission fluid. A full rebuild of the gearbox is by no means always necessary. In many cases, a targeted diagnosis solves the problem or makes it clear what the next step should be.
If you have symptoms, work through the following steps:
- Check the transmission fluid. Look at the colour and smell. Dark, burnt or cloudy fluid means it needs changing.
- Check the fluid level. Too low a level leads to insufficient pressure in the gearbox and increases the risk of slip.
- Inspect for leaks. Check the underside of the car, the cooler lines and the seals around the gearbox.
- Have the software and sensors read out. If there are dashboard warnings, a software update or reprogramming of the transmission control unit is sometimes enough to restore correct shifting behaviour.
- Have the valve body and solenoids inspected. If the steps above do not solve the issue, wear to internal components may be the cause.
Some Volvo owners report that jerky gear changes disappeared after a software update or reprogramming of the transmission control unit, without any mechanical parts needing replacement. This is especially the case when the symptoms are noticed early and the fluid is still in reasonable condition.
‘ Timely inspection often prevents an expensive rebuild. ’
Do not keep driving with ongoing symptoms
A slipping automatic gearbox will not fix itself. The longer you keep driving with clear symptoms, the greater the chance of increased wear to clutches, valves or other components. Timely inspection often prevents an expensive rebuild.
Have the transmission checked as soon as you recognise several symptoms at once, especially if there is also an active fault message. An authorised Volvo dealer or specialist transmission workshop can quickly establish what is going on with the right diagnostic software.
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Frequently asked questions
Look for whether the revs clearly rise without the car accelerating in proportion, and whether there are jolts, delays or messages such as “Transmission service required”; that more often points to a serious problem. Check the transmission oil for level, colour and smell: if it is dark, burnt-smelling or clearly too low, that is a bad sign. If the symptoms occur mainly shortly after a cold start and (temporarily) improve after gentle driving, it may still be an early or milder issue. If the symptoms worsen quickly or remain despite good oil, have the gearbox read and tested by a professional straight away.
The most common causes of a slipping transmission in a Volvo S90 are aged or burnt transmission fluid, a fluid level that is too low, and wear or contamination of internal components such as clutches and the valve body/solenoids. Simple and relatively inexpensive options are a fluid change or flush and fixing leaks; this is usually in the order of a few hundred euros. More complex and expensive jobs are rebuilding or replacing the valve body or the complete transmission, which can run into thousands of euros. The exact cost and complexity depend heavily on the type of automatic gearbox, the level of internal wear and whether additional damage (for example from overheating) has occurred.
Technically, it is only sensible to choose between rebuilding and replacement after a clear diagnosis: if the damage is limited (for example mainly contaminated oil or early wear), rebuilding is usually the best option, because you replace parts more selectively and save money. With severe internal damage or repeated problems, an exchange gearbox can make more financial sense, especially if the car is otherwise in good condition. If the S90 is relatively old, has high mileage and is facing several costly repairs, selling it may be the smarter financial option. Always have a specialist transmission expert provide a diagnosis and cost estimate before deciding.
What preventive maintenance is crucial to stop a ‘slipping transmission’ in my Volvo S90 in future, and can I do it myself?
The crucial preventive maintenance is changing (or flushing) the transmission fluid in good time according to, or preferably slightly before, Volvo’s recommended service interval. It is also important to have the fluid level and condition (colour, smell) checked regularly and to inspect the transmission for leaks. The level and – on some versions – a simple drain-and-fill can sometimes be carried out by an experienced DIYer, provided you use the exact correct oil, procedure and tightening torques. However, for full flushes, software updates and diagnosis of early slip, it is wise to have a specialist or dealer do the work.
A Volvo specialist often has specific knowledge of the automatic gearbox types used, known weak points, and the correct Volvo software and oil specifications, which can be crucial with a slipping transmission. A general garage may be cheaper for basic checks such as oil level, quality and leaks, but may sometimes lack access to brand-specific diagnostic equipment and updates. For complex symptoms, fault codes or doubt about internal wear, a Volvo specialist is usually safer, while a general garage is sufficient for an initial diagnosis or simple servicing. Also bear in mind warranty terms, service history and the availability of rebuild or exchange gearboxes through the chosen workshop.
