What Causes A 4l60e Transmission To Slip

metal flakes in 4l60e transmission pan - CPT 4l60e

The last thing that you want to feel when driving down the street is your transmission start to slip and miss shifts.  This not only is cause for concern, but depending on the root problem, can hurt your wallet.

There are three main factors that create 4l60e slipping issues including: fluid, wiring & computer issues, and broken or worn out hard parts.

With each of these areas, there are a number of reasons that your 4l60e is slipping, and each ones comes with its own associated list of problems.

Improper Fluid Level – Low On Transmission Fluid

Being low on transmission fluid is one of the most common reasons that your transmission is slipping.  With a low transmission fluid level, there is not enough fluid to properly perform shifts, and this causes a delay and potential slipping.

The silver lining to low transmission fluid is that this is easily fixed as long as that’s the only issue.  If your transmission fluid is low due to a leak somewhere, then obviously that needs to be addressed right away.

How to fix transmission fluid level issues:

  • Check and add transmission fluid
  • Repair any leaks (if applicable)

Fluid Worn Out and Burnt

Another reason your 4l60 may be slipping is because the fluid in the transmission is well past its regular maintenance interval and is worn out.  Overtime, transmission fluid breaks down and loses its friction properties, and this causes slipping symptoms.

In addition to fluid being worn out from poor maintenance, fluid that’s burnt also causes slipping.  Fluid that gets too hot breaks down fast, and the longer you let fluid “cook”, the worse it’ll cause issues.

How to fix worn out or burnt fluid:

Shift Solenoids Not Working

The shift solenoids in the 4l60e are responsible for routing fluid through the transmission that’s needed in order to make shifts.  Faulty shift solenoids may create lazy or no shift depending on how they’re working.

For the average DIY weekend mechanic, diagnosing shift solenoid issues is not easy, especially if you’re not too savvy with electronics and how they’re supposed to work.

How to fix shift solenoid issues:

4l60e Slipping in Reverse

The cause of your 4l60e slipping in reverse is more than likely due to worn reverse clutches.  This is easy to diagnose based on you not being able to move much in reverse but forward gears are ok.

Note:  If you recently changed fluid, or installed a torque converter, you may have other issues that cause reverse to be slow or lazy. In this case, you may confuse worn clutches with other issues such as low fluid or improper converter to transmission pump engagement.

How to fix 4l60e slipping in reverse:

  • Check fluid to see if low
  • Take vehicle to mechanic for further diagnosis

Not Holding Gear After Shift

Depending on the age of your 4l60e, it’s common that gears start to slip after completing the shift, and this is due to worn clutches.  Since the 4l60e has smaller internal components including clutches compared to other transmissions that are used in trucks and heavier vehicles, there is always a potential for worn or burnt out clutches over time.

How to fix 4l60e not holding gear after shift: 

  • Take vehicle to trusted transmission shop for diagnosis and possible rebuild

Torque Converter Not Locking

While this isn’t a problem directly caused by transmission parts, the torque converter not locking in overdrive can cause symptoms that feel similar to transmission slippage.  If the converter is not locking or is doing so intermittently,  this will cause RPMs to raise as you drive down the road that feel like 4th gear is slipping.

This is caused by one of two things:

  • Worn torque converter clutch
  • Malfunctioning TCC Solenoid

In most situations where the converter clutch is worn out, this will keep lockup from happening.  The biggest problem with this is that this may send converter clutch material though the transmission and cooling system, which will cause further damage.  It’s common to have a full transmission rebuild when this happens.

When it comes to the TCC solenoid not working, this is easier to diagnose compared to the converter clutch not locking since it is electronic and you can force via transmission software.

How to fix torque converter not locking issues: 

  • Take vehicle to transmission repair shop for diagnosis


If your 4l60e is slipping, sure, it’s a major problem, but you can easily diagnose most causes and get it fixed quickly. Depending on the cause it may be as simple as adding transmission fluid all the way to more serious issues that require a full rebuild.  If your 4l60e is older and has been put thorough its paces, then you got a good life out of it, and as we all know, the 4l60e is not going to last 300k miles (unless you’re lucky and great with maintenance and fluid cooling).