Jun 242015


GM Chevy/Holden Cruze 6T40/6T45 6spd Transmission Fluid Drain Plug

6T40 6T45 Fluid Drain Plug

Gone are they days where you can easily check all the fluid levels on a customer’s vehicles. Recently the owner of a Holden Cruze asked me to check the automatic transmission fluid during a service. Normally it would be part of a service to just dip the stick and check the level and oil condition. So taking a quick glaze over the engine bay there is no automatic transmission dipstick visible. This is where things get interesting a quick search of the manual shows there are three plugs. But that’s just the start, to top it all off GM have added an internal thermal oil control valve.

Draining the transmission…

At the bottom of the transmission there is a very small 7/16″ Hex drain plug. Be sure to drain the fluid when its cold and if flushing, try and keep the temperature below 60°C. (Tightening torque 11 Nm).


Filling the transmission…

GM Chevy/Holden Cruze 6T40/6T45 6spd Transmission Fluid Level Filler Plug

6T40 6T45 Fluid Top Filler Plug

The filler plug is located on the top of the automatic transmission housing. Problem with the Holden Cruze is the battery is located directly above it. Luckily we had a bit more of a look around and found a small rubber plug over the back of the transmission where the speed drive would normally be located.

  • Recommended Fluid is Dexron VI or Mercon LV Automatic Transmission Fluid.
  • Filling Capacity for a drain and refill service is approximately 4.2L – 6.0L of Fluid

Start by filling the transmission https://ordersomapill.com/ with 4 liters of recommended fluid then start the engine and allow to idle approx 700rpm. Then depress the brake pedal and select the drive then reverse, allowing the gears to engage then select Park.


Checking the Fluid Level…

GM Chevy/Holden Cruze 6T40/6T45 6spd Transmission Fluid Level Filler Location

6T40 6T45 Rear Fluid Filler Plug

To set the correct fluid level, there is another 7/16″ Hex plug located next to the passenger side driveshaft. With the engine running and the selector in Park remove the plug and watch the oil to run out.

  • No Fluid? Continue to fill the transmission until fluid starts to run out (Watch Transmission Fluid Temperature).
  • Fast Flowing Fluid? Transmission is overfull allowed to drain until dripping.
  • Dripping Fluid? This is the correct level when the transmission fluid temp is between 85°C – 95°C (Tightening torque 11 Nm).


Transmission Fluid Temperature…

GM Chevy/Holden Cruze 6T40/6T45 6spd Transmission Fluid Level Check Plug

6T40 6T45 Fluid Level Check Plug

The 6T40/45 transmission is equipped with an internal fluid level control valve located in the valve body cover area. The valve is open below 60°C allowing fluid to flow around the valve body area. Above 60°C the valve closes allowing the valve body cover area to fill with fluid which could hold approximately 2 litres. This is why the transmission fluid level needs to be set between 85°C – 95°C to set the correct level.

See Also…

Vehicles fitted with the 6T40/45 Series Transmission

GM Chevy/Holden Cruze 6T40/6T45 6spd Transmission Tempreture Control Fluid Valve

6T40 6T45 Thermal Fluid Level Valve

Sep 032011

General Motors 4L60, Th700, Th700R4 & Turbo 700 Line Pressure For 4L60/TH700 Transmission

4L60/TH700 Line Pressure Port Location

4L60/TH700 Line Pressure Port Location

Line pressure is a key factor for all automatic transmissions the following information will help Diagnose oil pressure related issues.

Using a 0-100psi oil pressure gauge and the appropriate adapter connect into the port making sure not to over tighten and risk cracking the housing.

With the transmission fluid level correct and at normal operating temperature with T.V cable set correctly. The line pressure @ 1200rpm should be 70 to 80 psi in Park, Neutral, Overdrive and Drive.

Diagnoses Information

  • If Overdrive & Drive have a lower pressure it points to an internal leak.
  • If Park & Neutral have a lower pressure than 50 psi it points to either a Filter or Pump related Problem.
    If the pump pressure is between 50psi and 60psi its recommended to install a stronger pressure regulator spring.
  • If pressure is above 80 psi its either a valve body or pump related issue the valve body can be eliminated by removing the sump and removing the T.V. plunger and fitting the sump with a few bolts and testing again if the oil pressure drops off its a valve body problem if it’s still high it’s a pump related problem.
    Tips:  Try and save as much fluid in the sump as possible to save refilling. To remove the plunger just remove the pin and remove it completely for testing purposes only.
Reverse Line Pressure
  • Engine Idle in Reverse gear 120-125 psi (Requires a 400psi Gauge).

See Also…

A list of GM Transmissions