Diagnose torque converter selenoid or transmission

have an 06 avalanche 1500 ls 2wd 5.3 automatic that will drive fine for 30 mins then suddenly lose acceleration rpms still move but wont increase speed on road but once it cools down half n hr or so it will drive fine again no clicks or noise no shifting problems and it is not producing any codes at autozone the transmission is only 3yrs old fluid is full but has a hint of dirt to it but not burnt black or metal still red and full no leaks im not sure where to start diy cant afford to have shop repair can u give me ways to test if its the tranny torque converter or selenoid or any other ideas
Experienced mechanics share their insights in answering this question :
Hi there. The computer could be putting the vehicle into limp mode due to an issue that may be happening and reduces the engine performance. Check the battery, alternator, and all of the sensors on the engine and make sure that they are all working properly. If the engine is running normally, then there could be an issue with the transmission.

To check the transmission torque converter complete the following steps:

(1): Set the parking brake and start the engine.
(2): Press down on the service brake and hold it on the floor
(3): Put the transmission selector in the ’D’ (drive) position
(4): Press down on the accelerator pedal to the floor for 3 to 5 seconds
(5): While the engine rpm is high, monitor how high the rpm goes with the accelerator pedal on the floor
(6): Let off the accelerator pedal and put the transmission in park
(7): Shut off the engine and then release the service brake and parking brake

Make sure that when you perform this test, have your vehicle in a location where there is nothing in front of the vehicle to prevent any damage to your vehicle if for some reason the brakes fail during the test. It is best to add a pair of chocks to the wheels for added safety. If you need further assistance with your vehicle stalling for no reason after 30 minutes of driving, then seek out a professional, such as one from Your Mechanic, to help you.

How to Identify and Fix Common car Problems ?

Our sources include academic articles, blog posts, and personal essays from experienced mechanics :

When the torque converter starts malfunctioning, you may feel shuddering and even slipping in overdrive. You usually notice your car shuddering because it feels like it`s vibrating. Your car will vibrate even when you`re not going very fast. The shuddering makes the car lag and is very noticeable.
General poor engine performance is common, as are issues with failure when shifting. You may also start seeing slipping of the gears and transmission overheating, with engine stalling also happening in some situations. Your vehicle`s check engine light will generally also turn on with this type of problem.
Measure the resistance of all solenoids. The TCC On/Off solenoid should be 12-28 Ohms. The TCC PWM solenoid should be 7-20 Ohms. The EPC solenoid should be 3-6 Ohms.
The best thing to do to confirm the problem is to test the torque converter. To test the torque converter, you must step on the pedal to the floor and accelerate your engine for up to five seconds. The reading for the revolutions per minute (RPM) will max out at the stall speed.
The lack of converter clutch function will not harm anything, but will cost a bit of fuel economy due to the torque converter slippage. The vehicle will behave just as all automatic transmission cars did prior to development of the torque converter clutch some four decades ago.
Turbine speed sensor (TSS)

The TCU uses the input shaft speed to determine slippage across the torque converter and potentially to determine the rate of slippage across the bands and clutches. This information is vital to regulate the application of the torque converter lock-up clutch smoothly and effectively.

There should be a click from the solenoid once the current is properly supplied. If there isn`t a click, the solenoid coil is bad, and the solenoid needs to be changed. To diagnose the solenoid, use a multimeter to test the solenoid for its resistance and voltage.
When a solenoid is first energized, its coil receives a pulse of high inrush current that decreases as the plunger closes. If the plunger does not close, the high inrush current continues, which can cause the coil to overheat and burn out. This is the most common cause of solenoid failure and spotting it is easy.
But a blown fuse No. 38 becomes a likely candidate causing a loss of power to the transmission solenoids.
For irrigation applications, a solenoid is considered to be good if its resistance is between 20 – 60 ohms. It is best to compare resistance measurements to that of a new solenoid. Example, if a solenoid measures 44 ohms, it would be considered good because it is between 20 – 60 ohms.
Computer and Internal Diagnostics

The AAMCO Computer Diagnostic Service is performed to determine if an electronic component is affecting your transmission`s shifting or overall performance and includes: Using a computer system scanner to retrieve any trouble codes and to determine the probable cause.

Solenoid resistance is 20 to 30 ohms and system voltage with the engine off should be about 12.6 volts, so a good circuit should develop about 0.63 to 0.42 amps of current flow (V/R=A).
Use the scan tool or scope to graph the TCC duty cycle and look for a saw toothed pattern that ranges from 40 to 80 per cent. If this style of pattern is displayed on the graph then the pressure control solenoid is out of range and is causing the chuggle/misfire.
When you have a bad starter solenoid, the starter motor won`t work. This means the engine won`t start when you turn on the starter switch or press the start button. However, if your vehicle has an automatic transmission, the engine could sometimes not crank because of the neutral safety switch.
The diagnostic trouble code or DTC P0740 stands for “Torque Converter Clutch Solenoid Circuit/Open Circuit Malfunction.” The error code basically means that the Powertrain Control Module (PCM) has caught some issue within the torque converter clutch (TCC) circuit (or torque converter clutch solenoid circuit).
A damaged fin or bearing in the torque converter can cause hesitation in the transmission shifting, or the transmission to slip out of gear entirely. This is because the engine torque is not being efficiently converted into the hydraulic pressure needed to shift gears within the transmission.
The likely culprit will be a faulty torque converter, and we recommend not driving the car until you fix it.
If your vehicle exhibits any of these signs of a failing torque converter, make sure to stop driving it immediately. A faulty torque converter can often result in significant transmission damage due to overheating or fluid degradation. As such, it`s important to replace your faulty torque converter as soon as possible.
The torque converter clutch solenoid is an electronic component that helps to measure the fluid pressure and regulate how much fluid the lockup clutch receives. If the solenoid is faulty, there won`t be an accurate measure of how much transmission fluid is a need which could lead to abnormal fluid pressures.
The torque converter can be found between the front of the transmission and rear of the engine. The torque converter clutch (TCC) is located inside this device. The TCC is a component made of a friction material, which locks the converter shell onto the turbine shaft.
Automatic transmissions use two or three solenoids and turn them on and off at different times to achieve different gears.
Solenoid coil failure can be caused by a number of factors. Applying an incorrect voltage to the coil will cause it to fail and may cause the coil to burn out. Electrical surges or spikes may also damage the coil. Burnt out coils cannot be repaired and will need to be replaced.
Manual Reset Solenoid Valves

This is what is known as Manual Reset. To cause the valve to change from its rest state, the coil must be energised and the lever or knob pulled to the fully open position. If the valve is energised without the manual intervention, it will not open.

Electronically controlled transmissions may contain more than eight linear solenoids, all of which require smooth, accurate control.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

Diagnose torque converter selenoid or transmission
ANSWER : Hi there. The computer could be putting the vehicle into limp mode due to an issue that may be happening and reduces the engine performance. Check the battery, alternator, and all of the sensors on the engine and make sure that they are all working properly. If the engine is running normally, then there could be an issue with the transmission.

To check the transmission torque converter complete the following steps:

(1): Set the parking brake and start the engine.
(2): Press down on the service brake and hold it on the floor
(3): Put the transmission selector in the ’D’ (drive) position
(4): Press down on the accelerator pedal to the floor for 3 to 5 seconds
(5): While the engine rpm is high, monitor how high the rpm goes with the accelerator pedal on the floor
(6): Let off the accelerator pedal and put the transmission in park
(7): Shut off the engine and then release the service brake and parking brake

Make sure that when you perform this test, have your vehicle in a location where there is nothing in front of the vehicle to prevent any damage to your vehicle if for some reason the brakes fail during the test. It is best to add a pair of chocks to the wheels for added safety. If you need further assistance with your vehicle stalling for no reason after 30 minutes of driving, then seek out a professional, such as one from Your Mechanic, to help you.

How do you remove the torque converter bolts off the flywheel? 2005 GMC Envoy Denali
ANSWER : Hello – with the vehicle safely supported to provide clearance underneath – in between the engine oil and transmission pan, there is a large, funnel-shaped aluminum casting (called the bellhousing), that physically mounts the engine to the transmission. At the forward vertical face of the bellhousing (immediately behind the engine oil pan), is an access plate – remove it. The engine flywheel/flex plate is now exposed. There will be 3-4 bolts, which go through the flex plate to the torque converter, which hold the torque converter to the engine flywheel/flex plate. Turn the crank from the front crankshaft pulley bolt (CLOCKWISE facing the nose of the engine) a bit, remove a bolt, turn the crank a bit further, remove the next bolt, etc. until all the torque converter bolts are removed. At this point, you should be able to slide the torque converter toward the rear of the vehicle 1/4-1/2" by hand. This will confirm that all bolts are out. You will also be able to rotate the torque converter by hand, without turning the engine. Remember this when re-assembling the engine/transmission, and it becomes to rotate the torque converter to line up the bolt holes in the flex plate. Proceed with the removal of the transmission.

Need torque converter specs because I just replaced the transmission.
ANSWER : I’m not sure what you mean by torque converter specs. Torque converter end-play can be checked with a special tool and a dial indicator. This is done to determine the lateral movement of the turbine and stator. The repair information I have does not list this specification. If you have any doubts about the converter, I recommend replacing it. More often than not, the converter suffers contamination as a result of internal transmission failures and should be replaced anyhow.

Transmission fluid fine but it takes torque converter long to to lock up
ANSWER : Color doesn’t always matter. You might decide to service the transmission. I would say change the filter and change the fluid and see what happens. You might add a quart of Lucas transmission additive into the mix and then drive it for 2-300 miles and see if it helps. Because I’ve done that personally on many cars. A lot of times, especially with GM product like that, that would solve it. Change it and put a quart of Lucas into the mix. If you need help with this, a certified technician, such as one from YourMechanic, can come to your home or office to inspect your car and service your transmission fluid if needed.

I changed out my torque converter and didn’t unhook the battery and when I put the transmission back in it spark
ANSWER : Vehicle electronics are very sensitive to voltage spikes. Start with checking any and all fuses, particularly those to things like ignition, fuel, and ECU. If all fuses are good, then you will have to start more extensive diagnostics. There should be a fusible link down by the starter that may have burned/blown. They are in place to protect for things like voltage spikes, however, they aren’t a guarantee that other vital electronics were not damaged. Check relays for the fuel system, ignition system, etc. The voltage spike may have shorted the the engine control unit and/or the powertrain control module. If you need help having this diagnosed, a certified technician from YourMechanic can come to your home or office to inspect your starting issue in order to have the correct repairs done.

2013 Ford Focus Transmission Issue. Is it worth keeping the car?
ANSWER : Hi There,
This is a known issue in this generation Ford Focus and some Fiestas with the "Power Shift" transmission and there have been numerous recalls and lawsuits. Although, it is would be difficult to determine how much longer your transmission will last given the fact that you have many new parts, I would not recommend junking the car as it may still provide some valuable life left for you. I would recommend taking it to the dealer to see if these parts may be covered under the recall.

Bought a 1999 Chevy Z71 for very cheap. The transmission is out. How should this be fixed?
ANSWER : Hi there. The 4l60e transmission could have two things wrong with it. Either the park arm is not disengaging inside the transmission making the transmission load up but not rotate the drive shaft or the transmission is low on oil. Check the oil on the transmission dip stick and see what the level is. The level must be checked with the engine running. If the oil level is at the full mark, then it is possible that the torque converter may have damaged the pump.

Remove a cooler line and put it into a bucket, and for a brief moment start up the engine and shut it off. If oil sprays out of the cooler line, then the pump is producing pressure. However, if no oil comes out of the cool line, then the pump is not working.

If you need further assistance troubleshooting your transmission, then I recommend having the transmission problem diagnosed by a local expert, such as one from YourMechanic. You will be be able to make a better decision about the car after finding out exactly what’s wrong with it.

There is automatic transmission fluid in a manual transmission. Is it okay to leave or do I need manual transmission fluid?
ANSWER : This would depend on what the manufacturer recommends. Many manual transmissions do take automatic transmission fluid. If your transmission has ATF in it, it is very likely that it is supposed to have that in there. If not, it is likely that the transmission would not function properly with the wrong fluid. Many manual transmissions will also take engine oil as a lubricant. The best way to know for sure is to check your owner’s manual or call your local General Motors dealership to inquire.