General Motors 4L60, Th700, Th700R4 & Turbo 700 Line Pressure For 4L60/TH700 Transmission
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.
- 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.
- Engine Idle in Reverse gear 120-125 psi (Requires a 400psi Gauge).