Skip the auto shop - Our mechanics make house calls

Q: Torque converter goes in/out of lock up at cruising speed

asked by on

My SUV’s torque converter goes in and out of lock up when going a steady cruising speed. While driving a constant 65 mph, on level ground, the engine RPMs will go from 1700 to 2000 and then back again. It acts as if it is hunting between gears; however, the transmission is in top gear. Can you give me ideas of how to solve this problem?

A: Thanks for writing in about your 1999 Chevr...

Thanks for writing in about your 1999 Chevrolet Suburban. There are DTCs (diagnostic trouble codes) that will indicate faults with TCC solenoid and brake pedal switch circuits. A scan tool can be used to observe brake pedal switch position while driving to determine if this is the input causing the TCC to disengage. The state of command to the TCC solenoid can also be monitored during test drive to help diagnose the rough cruising speed acceleration.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: How do I customize the Vehicle Locator Lights?

The vehicle locator lights can be turned on or off with just a few steps: 1. Turn on the infotainment system. 2. Press the CONFIG button to select the Configuration Settings menu. 3. Rotate the MENU/SELECT knob to Vehicle Settings,...

Q: Engine trouble

First thing to do is to get the oil level back up to where it's supposed to be, and keep track of how much it takes to do so. If you have to add more than half the oil change...

Q: Crank, No Start, replaced fuel and relay.

When you applied power to test the pump directly, you may have had the power and ground backwards, and ran the pump backwards. The pump connector that is only getting 8 volts should be replaced. The connectors are known...

Related articles

How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.