Third Generation Challenger Transmissions & Trans Parts

Apart from the fact that the newer Torqueflite 8-speed transmissions are significantly better than their 4 and 5-speed antiquated brethren, it is difficult to concretely determine which is the best due to there being so many variables. If you want to know which is the best in terms of raw performance then it would be the 8-speed automatic that takes the cake.

Given its lightning fast shifts and active torque management capabilities, automatic equipped Challengers are likely to rip off the best times at the drag strip autocross track and street. Now in terms of fun factor, it is my personal belief that a manual gearbox can't be beat... but it will leave some time on the table.

Torque converters are mated to automatic transmissions and serve two purposes: 1) to transfer the engine power to the transmission and; 2) to let the engine continue running when the car is at a stop. It uses a hydraulic fluid coupling to achieve this and is capable of torque multiplication when there is a difference between input and output speed. 

There are three basic components to a torque converter: a pump, a turbine, and a stator. The converter housing is attached directly to the engine flywheel and the interior of the housing is lined with specially angled fins - these fins serve as the pump. When the housing spins, the blades fling the transmission fluid to the outside of the housing (due to centrifugal force) and thereby creates a vacuum in the center which is used to draw in more fluid. The fluid is pushed to the turbine, which is connected to the transmission. The turbine also has specially angled fins that are designed to change the direction of the fluid by the time it is exiting the turbine. As the turbine spins, it moves the input shaft of the transmission which then is transmitted to the wheels. The stator sits in the middle of the converter, sandwiched between the turbine and the pump. Its job is to reorient the fluid coming from the turbine (this fluid is now moving in the opposite direction of the pump) as it passes back to the pump.

A torque converter has three operating conditions: stalled, acceleration, and locked. A stalled condition is when the converter is spooling, but no transfer is being made to the transmission. Converters are rated at a certain stall speed, but this speed does not signify the point at which the car will move. Rather, the stall speed is simply the RPM at which the converter can no longer hold back the engine (can no longer stall the engine) if transmission output is prohibited (on the brakes).  

The acceleration phase has the Challenger moving, but there will be a sizeable difference between pump and turbine speed - the pump will be spinning faster than the turbine (similar to a clutch slipping). Torque multiplication occurs during this stage.

Finally, the lockup or coupling stage is when the turbine is within 90% of the speed of the pump. A lockup clutch will actuate and lock the turbine to the pump, thereby creating a 1:1 spinning ratio. No torque multiplication is occurring as now the transmission is connected directly to the flywheel speed.

The reason behind swapping to an aftermarket torque converter is to obtain a different stall speed. Aftermarket torque converters come with a higher stall speed than stock, which allows the engine to spool into its optimal powerband before launching the car. This translates to better acceleration off the line and to significantly better 60 ft times. Calculating and deciding on stall speed is a complicated process as there are very many variables to consider. Engine power and torque delivery, camshaft profile, transmission, and rear end gearing, intended use of the Challenger - these are just some of the factors that must be examined when determining a new stall speed converter. Thus if you are looking to upgrade your Challenger's converter, you should seek the advice of a professional in order to make the optimal choice.

Concerning the automatic transmissions, there are no aftermarket shifters available. Given the complexity and computer-controlled nature of the transmission, the stock shifters are adequate. If looking for better performance out of one of the automatics, a lot of tuning can be done via a handheld tuner (shift points, firmness). If this is not enough, aftermarket performance valve bodies and solenoids are available that will harden and speed up each shift.

In terms of the Tremec TR-6060 manual, aftermarket shifters are available. The factory shifter already has a pretty low throw distance, however there is some slop in the throws due to the shifter lacking centering springs and inherent looseness in the shift rod linkage. An aftermarket shifter will correct these problems and enable faster shifting and eliminates the common problem of missed 2nd-3rd shifts.

Manual-equipped Challenger owners will be happy to hear that the answer is no. A manual transmission does not produce anywhere near the amount of heat an automatic transmission and thus does not need a cooler at all. 

Turning to the automatic-equipped Challengers, they absolutely should be using one. In fact, Dodge does incorporate a basic transmission cooler into the OEM design. Depending on the year of the Challenger, a small cooler is either integrated into the lower radiator or the A/C condenser. As too much heat is detrimental to the life of an automatic transmission, keeping the fluid cool will ensure longer life and better reliability. If the temperatures are getting too hot (measured by onboard diagnostics or through the data center), upgrading to a larger aftermarket cooler is the smart choice. Even better, aftermarket coolers are not very expensive and are fairly easy to install. They just need to be mounted and the cooling lines connected to their respective port.