Transmission Slipping: Causes & DIY

Transmission slipping can be a major issue, especially for automatic cars and less so for manual transmissions. If your car is showing signs of slipping then you need to get it fixed quick. What can start off as a small problem can easily turn into a bigger issue later on that will cost even more money to fix. Slipping does not necessarily mean that your transmission is near failure but it is signalling that maintenance is heavily required. For automatics there can be many different causes while for manuals the problem is often associated with the clutch. Here are the common causes of a slipping transmission and how to fix it yourself.

Symptoms of Transmission Slipping

Although diagnosing for slipping is not always easy, there are a few common signs that you should look for. Signs of slipping can appear in a number of forms when you are driving. Signs include a high RPM (over 3,500), delays in acceleration, inability to reverse, unusual or burnt smells, the check engine light going off, difficulty shifting gears, shifting gears produces a harsh response, or any strange noises. If you experience any of these symptoms then your car is likely showing signs of slipping. There are a handful of possible causes for this and if you can find the exact reason soon then you have a chance of fixing it without further damage to the transmission.

Common causes of transmission slipping:

  • Low fluid levels – The most common cause for slipping is low fluid levels. Low fluid levels can create a number of problems, such as overheating and not enough hydraulic pressure being produced to engage gears. The best way to find out whether you have low fluid levels is to check the fluid, which you can read below. If this is the case then you will have to add more fluid in order for the gears to engage properly, although low fluid levels could also indicate a transmission fluid leak.
  • Burnt or ineffective fluid – Burnt fluid can be distinguished by the smell of burnt toast or a color that is black. Burnt fluid occurs because of overheating, which means you will have to change the transmission fluid quickly or have it looked at by a specialist in order to diagnose for further damage. Ineffective fluid is similar to burnt fluid in that it has lost its effectiveness, but this is often because of too many contaminants or just from normal wear and tear. Though this doesn’t always mean transmission problems, a fluid change should be performed in order to stop slippage. Both burnt and ineffective fluid can be tested by checking the fluid.
  • Transmission fluid leak – If you experience low fluid levels, this could indicate a transmission fluid leak and transmission slipping is likely to occur. A leak can occur anywhere though, such as a leak in the pan, ruptured fluid lines, a worn pan gasket, a crack in the torque converter, or faulty seals. Continuing to run your car with a leak can cause serious internal damage and you need to seal it up quick. Check underneath your car and on your driveway for any signs of leaks. Seal leaks can be eliminated with special friction modifier additives.
  • Worn or broken transmission bands – Sometimes transmission bands can become worn or broken, which can cause transmission slipping not to mention engine troubles or worn gears. Bands are what links the gears in the automatic transmission together, so they can’t be overlooked. To remedy this problem you simply need the defective band replaced or adjusted, although Lucas Transmission Fix helps to renew worn transmission bands.
  • Clutch problems – Automatic and manual transmissions both make use of clutches. Automatics have clutch plates throughout the transmission and in the torque converter that may become worn or burnt from inadequate transmission fluid. You will have to get these replaced ASAP and change the fluid. For manual transmissions, clutch problems are the most common causes for transmission slipping, which is the culprit 90% of the time (the other 10% being leaks). Worn out clutches that have become too thin occur the most, while clutch failures and bad clutch adjustments are rare but do happen. Normally a clutch disc will last anywhere from 20k to 200k miles, so you will have to get worn or burnt ones replaced.
  • transmission slipping gears - transmission repair guyWorn out gearsOver time gears can wear out, due to normal wear and tear or a malfunction of some sort. Worn or frayed gears don’t properly link together which why they need to be replaced.
  • Solenoid problems – The solenoid is an electro-hydraulic valve, and its function is to control the flow of fluid throughout your transmission. Any damage or electronic problems can cause the wrong amounts of fluid to be dispersed. If you have already checked for low fluids or leaks, the solenoid would be your next suspect. You can check to see if this is the problem by plugging in a scanner to your car’s computer. If the solenoid is the problem you will have to fix or replace it. You can read more about transmission solenoids here.
  • Torque converter issues – Torque converters are what adapts the engine’s power into torque that the transmission can use and sometimes they can develop problems. Fluid flows through the torque converter, so if it fails to do that then your transmission will act funny and transmission slipping is often a symptom. This can be harder to repair and will need to be examined by a technician. You can read more about torque converter issues here.

How to Fix Transmission Slipping

You can solve transmission slipping yourself if it’s simply low fluid, burnt or ineffective fluid, or transmission leaks. This will often require you to either check the fluid, change the fluid, or fix the transmission leak, although these procedures don’t require a lot of experience with cars.

On the other hand, problems such replacing or adjusting clutches, replacing or adjusting bands, and replacing gears will require you to dismantle the transmission and know where the parts are. These procedures are complicated to explain and will require experience with cars. If you are a novice with transmissions, it’s best to have them done by an expert. The rest such as solenoid or torque converter problems that are causing transmission slipping are best left for a professional mechanic to fix. But for the simple issues, we will briefly explain the process and you can read the full tutorial later on.

Low fluid levels

What you will need:

The process:

  1. low fluid levels - transmission repair guyStart the car to warm up the transmission fluid.
  2. Pop the hood up and remove the transmission dipstick.
  3. Make sure that the fluid is in between the two marks on the dipstick, which are usually labelled “Full” and “Add” or something similar.
  4. If the level is below the lower line then you will need to add more of the specific fluid through the transmission reservoir via a funnel. Make sure not to overfill. If the level is significantly low, this could indicate a leak.
  5. Check again for transmission slipping.

For the complete tutorial click here.

Burnt or ineffective fluid

What you will need:

The process:

  1. Check the transmission fluidburnt or dirty transmission fluid for fluid that is either dark brown with particles or black with a burnt smell.
  2. If either are present, elevate the car on jack stands or ramps and warm up your car.
  3. Drain the fluid into a drip pan or container and remove the transmission pan.
  4. Clean the pan and magnet thoroughly.
  5. Replace the filter.
  6. Replace the gasket if it is old and worn and re-attach pan to the transmission.
  7. Add new transmission fluid by measuring the old fluid you drained.
  8. Check again for transmission slipping.

For the complete tutorial click here.

Transmission fluid leak

What you will need:

The process:

  1. Identify the cause of the leak, checking in common areas.
  2. Determine if the leak can be fixed yourself or should be brought to a mechanic.
  3. Gather the supplies and tools you will need.
  4. Drain the fluid into a drip pan or container.
  5. Depending on the problem, resolve it by following procedure.
  6. Replace the gasket if it is old and worn and re-attach pan to the transmission.
  7. Add new transmission fluid by measuring the old fluid you drained.
  8. Check again for leaks and transmission slipping.

For the complete tutorial click here.

How to Prevent Transmission Slipping

To prevent your transmission from ever slipping, you need to regularly maintain your vehicle. This means that you should check the fluid often for any signs of problems, such as leaking, low, dirty, or burnt fluid. Any of these signs can lead to transmission slipping so check the fluid once a month to prevent that. You should also get a transmission fluid with filter change every 30,000 miles or 2 years, whichever comes first. This makes sure that the transmission is always running on fluid at tip top shape.

Remember, low fluid levels, burnt or dirty fluid, and transmission leaks are the most common causes of transmission slipping, so if you make sure that none of these are happening then you can avoid slippage the majority of the time.