Failed automatic transmission : symptoms of the most common automatic transmission problems. How to do the automatic gearbox stall test and other do-it-yourself checks.
How to do the automatic gearbox stall test
The stall test of the automatic transmission is a very useful test, able to report the correct functioning of the automatic transmission or to detect a breakage .
The automatic transmission stall test can be performed by anyone. You don’t need any special experience, you just have to follow these instructions; better to do the stall test with the car already hot … maybe you can do it as soon as you return from work!
- Check that the automatic transmission oil level is correct.
- Check that the engine coolant level is correct.
- Apply the parking brake (hand brake) and depress the brake pedal.
- Move the automatic gear selector lever to position D or R.
- Accelerate fully.
As you accelerate, the automatic transmission overheats and the engine revs up until it stabilizes at a maximum value called stall . If this value is too high, undoubtedly there will be problems with the automatic transmission .
The stall is between 2,000 and 2,700 rpm depending on the type of gearbox. At this stage, watch out for the lap counter! If the car exceeds 3000 rpm, release the accelerator pedal immediately!
Engine RPM is your health indicator. The maximum speed will be the lower the better the automatic transmission works !
The maximum speed, in fact, is reduced by the turbine of the converter which is indirectly connected to the wheels. With the handbrake applied, the turbine of the automatic transmission converter will be stopped.
The turbine of the automatic transmission converter is connected to the wheels via the drive shaft. The pump of the automatic gearbox converter is connected to the crankshaft, this interconnection reduces the maximum revolutions of the crankshaft… So, when the vehicle is stationary, if the automatic gearbox is not faulty , the maximum rpm should be low.
The automatic transmission stall test can be performed in R or D depending on which clutch needs to be checked. If problems with the automatic transmission occur in both the R and D positions, the breakdown is likely associated with the torque converter and not the clutches.
When you have finished the automatic gearbox stall test , move the selector lever to N and run the engine for at least 30 seconds at idle to allow the torque converter to cool.
How to interpret the results of the automatic transmission stall test
If the RPM is high in both D and R, the problems could be with the oil pump, oil filter, leaks or it could be low line pressure. The high rpm is due to an automatic gearbox failure even in the event of slippage of one or more clutches.
Failed automatic gearbox, how to prevent breakage
In most cases, the failure of the automatic transmission is associated with poor maintenance. When was the last time you checked the automatic transmission oil? Automatic transmission oil not only lubricates, but activates the clutch packs and provides cooling at high revs.
When the oil loses viscosity, the automatic transmission is more subject to wear and, inevitably, it will cause you problems .
In any type of automatic transmission , the oil must be changed at least every 50,000 km and never beyond this limit! If you have not changed the oil in a long time, the filter should also be changed along with the oil.
How to clean the automatic transmission
To clean the automatic transmission and the oil circuit, it is possible to use special additives. On the market it is possible to find cleaning and protective additives.
The cleaning additives allow the washing of the automatic gearbox and the lubricating circuit, similarly, also the so-called “protective additives” clean the oil circuit but act by decreasing friction. By way of example, here are two cleaning and protective products to extend the life of the automatic transmission.
Useful links from Amazon:
- LiquiMoly, cleaner for automatic transmissions
Price: 19.08 euros, with free shipping - Protective additive for automatic transmission
Price: 22.00 euros, with free shipping costs
If your automatic transmission is broken , it would be utopian to think of a miraculous recovery thanks to an additive. Washing with additive is undoubtedly positive for the lubricant circuit of the transmissions but in case of breakage already verified it will not work miracles. Additives only serve to prevent breakage and extend the life of mechanical components.
How to use the protective additive? Reduce the oil levels and add 10% of the product for each liter of oil.
The cleaning product dissolves the encrustations of the old condensed oil while the protective product improves the performance of the converter and reduces internal friction, preventing the automatic transmission from breaking .
Automatic gearbox replacement, costs
In the event of an automatic transmission breakdown , if repair is impossible, it may need to be replaced. Replacement is not cheap at all and the cost of a new automatic transmission varies greatly depending on the car model and manufacturer. For a Fiat, Citroen, Ford, Peugeot automatic gearbox, the cost starts at 4,000 euros. For a faulty automatic transmission from BMW, Audi or Mercedes, costs start at 4,700 euros
