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While the 4L60E may be one of GM’s most reliable transmissions, nothing is without fault. Everything has the potential to fail, but there are rarely problems without solutions. Below will be some problems that can occur within the 4L60E transmissions and also potential solutions that can be of use. Also mentioned will be ways to identify the type of transmission you may have so the problems can be assessed and solved correctly.
Now, while most or all 4L60E transmissions seem identical to the untrained eye, there have indeed been changes over the years to distinguish them from other models. Launched in 1992, the 4L60E has kept some features the same, such as a 12-pin connector from the harness. However, the color of this connector can still differ based on the year of the model, being either purple or green. Some other constant features include being shifted by the vehicle’s ECM, or engine control module, essentially the brain of the car, and each of them share the same type of casing coating the transmission, that being a cast aluminum build.
While the 4L60E does have some features that remain the same, with the passage of time comes improvements to the original model. There have been three distinct eras for the 4L60E: the original run from 1993-1997, having taken over from the 700R4, otherwise known as the original 4L60 with the hydraulic control over the electronic that General Motors uses today, the second being from 1996-1999, and the most recent beginning at the turn of the century in 2000. The original 1993 model only used one piece case while the 1996 and 2000 models have two pieces for their casing.
Besides the casings, there are smaller, though still important, methods of differentiating the transmissions. The main way to identify the model is to take a look at the bellhousings. More bolts were added between the upgrade in order to tighten up the grip to the transmission and the engine itself. Where the 93-97 model had 6 bolts to connect to the engine, the 96-99 has 9 bolts. In addition to this method of identification, the design of the bellhousings changed with the year of the model. These differences may seem small, but that does not change the fact that they are present.
A major change on the 2000 model was the size of the input shaft and torque converter. Prior to 2000, it had been 298 millimeters on both the 93 and 96 models, but when 2000 rolled around, the size was increased to 300 millimeters even, making it incompatible with any of the earlier models. Along with this, the size of the actual transmission was increased as well, being ¾ of an inch larger than before. These changes were implemented due to a new series of engines being rolled out around that time, the LS series. While these changes may seem miniscule and irrelevant, they still greatly affect the way the transmission works in the vehicle.
One of, if not the most common problems that the 4L60E transmission comes across is found in the reverse gear. Many have found the gear either slips or is not functional in the first place. This can be due to the low reverse clutch being worn out, for one, and there is debris falling into the transmission pan, which should then be emptied and then try using the reverse gear again. If this is not the case, then looking at the valve body would likely be the next possible source. The problem here would be a leak in the reverse circuit, thus a loss of fluid going towards the gear, causing a blown gasket or even the body itself being warped. If none of these are the cause of the issue, the last place to check would be the booster valve. This could be experiencing wear or even simply be stuck in place. Possible repair solutions may be, depending on the issue, removing and examining the checkball, though this process does involve removing the valve body so use caution when attempting this method, or using a high viscosity additive or other product to restore the seal.
Another common problem that might occur in the 4L60E is the shifting between first and second gear is late or sudden, with no ease between. This happens when the shift does not happen until you let off the gear. This is likely due to the throttle position sensor, or TPS for short. This is responsible for sending a signal to the electronic control unit when the throttle valve is closed or wide open. To test whether the TPS is operational or not, use a volt meter. With the car running, check the voltage. If it increases and decreases smoothly, then the TPS is fine. If the line is not moving smoothly, then the TPS will need to be replaced.
One other common failure in the 4L60E is the 1-2 accumulator. This is found between the shifting of first and second gear. If the vehicle is experiencing rough shifts between gears or if the shift is delayed in any sort of way, the accumulator is likely the root of the problem. In order to investigate this, there are a number of options, usually to maintain the upkeep. These include the spring, making sure that is in order, checking the accumulator piston for cracks, and the bore that the piston rides in. Here, the key is to look for any scuff marks.These might signify that the bore is experiencing significant wear and tear. To correct this, clean the inside with an emery cloth and finish with Brake Clean after this.
A major problem that some vehicles may encounter is when there is no movement in any gear whatsoever. The root of this problem is, more than likely, a failure in one of the pumps, causing a total loss of the fluid flow to the transmission. In this case, it is best to avoid running the engine until the transmission is refilled so the pumps are not being damaged. To check if this is indeed the case, make sure the engine is off and then check the fluid level and then once more while the engine is running in order to see how the flow is. If the level is not going down while the engine is running, then that means the fluid is not flowing properly and the pump is damaged or even completely broken. The best way to go about this is to refill the pan and find the leak at the source of the worst leakage areas and repair the pump from there. If this does not work, then the next best option is to remove the transmission and either rebuild or replace the damaged pump at the source and then put the transmission back in place.
If the transmission will not shift to a higher gear or if the speedometer will not go up, then this is a sign that the VSS (vehicle speed sensor) has failed. The VSS is responsible for sending how fast the car is meant to go to the ECM so the car will go that designated speed and is located on the rear end of the transmission. When this fails, the speedometer will not be able to read any of the speed changes in the car, posing a danger to the driver and those around them. Unfortunately, not much can be done to fix this and usually requires the device to be removed and replaced.
When a car suddenly begins to slow down, but does not stop fully, then it is likely running off of limp mode. This is a standby circuit in a car when there is trouble with the electronics system and the car enters a state of slow driving to maintain power. This is sometimes used by law enforcement officials to catch thieves in the act and recover them easily, but if this happens in your own car, then something might be wrong with the electrical system, likely a short. To check for this, pop the hood and examine the necessary fuses, replacing them if needed. If the problem continues, trace the wiring for the short and fix the problem there at the source.
If you find your vehicle unable to move into 1st or 4th gear, but the transmission is still automatically shifting fine otherwise, then the problem could be in the shift A solenoid. The solenoid is a magnetic device used to operate some unit. A moveable ion core is placed inside a coil of wire which moves due to magnetic attraction when there is an electric current that is being fed to the coil. To remedy this, remove the pan, replace the solenoid, and test the wiring again from the transmission and to the PCM (Powertrain Control Module)
This is very similar to the issue listed above in the solution to take to repair the issue at hand. If the car is slow to start moving, rolls on occasion, but starts fine if the vehicle is manually shifted into 2nd gear, then the problem is within the shift B solenoid. As stated above, the solution is to remove the pan, replace the solenoid, and test the wiring to make sure everything is operational. The break in the wire is usually a result of excessive vibration or a spike in the voltage. A proper solenoid should give 20-30 ohms of resistance. If not, the wiring is likely broken.
When the gears do not have firmness to their shifting, then the whole overall performance of the vehicle has begun to suffer. This is likely a case of either a leak in the boost valve, which is responsible for creating pressure, or the EPC (Electronic Power Control) filter is clogged. This can prove dangerous for drivers, as this signals that the vehicle is in need of a repair as soon as possible. For this, use a Transgo HD2-C kit, which does not require the transmission to be removed, making it the optimal choice. Otherwise, try seal restorer to the unit. If this does not help, a full rebuild may unfortunately be required on the system.
Some drivers have had issues with starting their cars in any other gear besides third, though are still able to shift while moving and does indeed work when the engine has been able to cool off. This has stemmed from vehicles where the VSS has dropped off. The cause of this is generally from reckless drivers “hotdogging” their vehicles, meaning gunning the engines while braking. Most GM shops should be able to help repair this by reprogramming the PCM.
While examining the vehicle is one way to diagnose problems, in the 4L60E and other GM vehicles, there exists a method for the vehicle itself to find the problem. This is done through the use of trouble codes. These are numerical codes that that the engine control module, the brain of the car, displays to identify a possible issue in the vehicle. The ECM questions various sensors in the vehicle, testing to see if that specific function is operational or if there is some issue. To initiate this process, start with the ignition turned off, as you will be working with jumper cables. Locate the Data Link Connector, found under the dash, and connect the cables to the A & B terminals. When this is completed, turn the ignition on. The Check Engine or Service Engine light will begin to flash. The first number of flashes that the light gives before a pause indicates the first digit and the second number of flashes after the pause will be the second digit. So, for example, if there are 6 flashes, then a pause, then 4 more flashes, then the trouble code will be 64. Listed below are some examples of trouble codes and their corresponding error.
21: TPS Circuit