Dodge Challenger & Charger. Randy Bolig

bolted to the torque converter housing. The stator shaft is pressed into the housing and is positioned with splines, which prevent it from rotating. The electronic control unit is bolted underneath the oil pan.

      On early models (2003–2005), some owners experienced transmission “shudder.” At that time, Technical Service Bulletin 21-011-05 was issued; it was later superseded by 21-003-06. This bulletin applied to LX and LE vehicles equipped with an NAG1 transmission (sales code DGJ) built prior to December 2005 with a transmission build date of July 8, 2005.

      The shudder condition may have been because of the torque converter clutch continually sticking and slipping because of contaminated transmission fluid. The transmission fluid contamination was thought to be caused by water getting past the transmission filler-tube (dipstick tube) seal. Depending on the amount of water in the transmission oil, car owners experienced a transmission shudder or vibration and/or an audible high-frequency buzz-like sound.

       If you wanted a car that allowed you to row-your-own in the shifting department, you didn’t order a Charger. All manually-shifted Challengers (manual not available in Charger), came with the TR-6060. The Tremec-sourced TR-6060 6-speed manual transmission is derived from Tremec’s T-56 6-speed manual transmission. It’s a stout piece that is rated to handle 700 ft-lbs of torque. The T-6060 is a “double overdrive” transmission, with .74 fifth-gear and .50 sixth-gear overdrives. (Photo Courtesy Tremec)

      The shudder/vibration or buzz-like sound was most noticeable during light driving (cruising) in 3rd, 4th, or 5th gear. The fix was to flush the transmission thoroughly (Chrysler recommended three times) and install a new filler-tube seal. Some owners flushed the transmission and simply applied RTV to the seal area.

      A popular and simple modification to the NAG1 is to replace the OEM-supplied brown-top solenoids with AMG blue-top solenoids as on the stock valve body. The blue-top solenoids have larger ports and provide firmer and faster shifts over the OEM brown-top units. If you are looking for even firmer shifts, a shift improver kit is also available but requires a little more work to install.

       Tremec TR-6060 2008–2014

      The 6-speed Tremec TR-6060 manual transmission was derived from its predecessor, the T-56. Dimensionally, they fit within the same location, but the T-56 was never used in the Challenger.

      Upgrades from the T-56 include reduced friction while shifting, thanks to a new cam and antifriction plunger to control the side loading of the shift detents. The forward and rearward shift-detent grooves are broached on the front of the main-shaft with a spring-loaded anti-friction roller. This gives a more positive shift feel. In addition, anti-friction ball struts, sintered hubs, and fine-pitch splines on all synchronizers also help reduce friction between the components. The two-piece gears are wider and have machined teeth for more precise gear engagement and reduced potential for gear block-outs and missed shifts.

      To use a manually-shifted transmission in the Challenger, Dodge looked to the already proven TR-6060 that was used in the Viper. Internally, the TR-6060 comes with triple cone synchronizers for first and second gears, and then twin cone synchronizers for third through sixth gears. These multi-cone synchronizers greatly reduce shifting effort.

      The clutch chosen for use in the Challenger was also sourced from the Viper. It is a 250-mm twin-disc design that is capable of delivering great torque-handling capacity and clutch life. The TR-6060 features a first- through fourth-gear skip-shift property, reverse inhibit solenoids, and a 5:1–ratio shifter.

      TR-6060 Gear Ratios

      

      As usual, the helical-cut forward gears are synchronized, but the reverse gear operates through a fully synchronized constant-mesh system. The TR-6060 contains removable wear pads on the shift forks and uses an aluminum alloy for the main case, extension housing, and clutch housing. In stock form it is rated for 600 ft-lbs of torque.

Rear Ends

      When the LX cars were released in 2005 (and the Challenger in 2008), Chrysler needed to find a rear end that would hold up to the performance demands of the new Hemi but still deliver uncompromising ride quality. For years before the introduction of the LX cars, a solid, or “live,” axle was used. A live axle is a rigid rear end that connects the two rear wheels. The axle shafts are within tubes that are connected to the differential housing.

       The rear suspension and differential on Chargers and Challengers is one complete module that is isolated from the body via bushings. It was initially designed to be compatible with parts from Mercedes-Benz. The five-link rear suspension offers a better ride quality than a traditional solid or live rear axle. The multiple suspension links maintain independent control of each rear wheel’s camber and toe angle during suspension movement. The entire rear suspension module is mounted to the body with bushings and can be removed as a complete unit.

      Because this type of axle is solid, when making a turn under severe cornering the wheel on the inside of the corner tends to lift. At the very least, the tire’s angle to the asphalt changes, minimizing the tire’s contact patch with the road surface. Also, when a wheel on the passenger’s side of the vehicle hits a bump, it channels that energy to the wheel on the other side of the vehicle.

      The differential on an IRS is rigidly mounted to the body, and the axles are connected to the differential and wheels via constant velocity (CV) joints. With the differential rigidly mounted and the wheels “suspended” individually they can move independently of one another. So, when energy is created as one wheel hits a bump, it is isolated only to the wheel that has to travel over the bump. Suspension travel of an independent suspension system also allows the tire to remain perpendicular to the road surface, maximizing tire contact with the road during hard cornering.

      Although the Charger and Challenger use IRS, solid-axle suspension systems aren’t all bad. They are significantly less expensive to build than an independent suspension because they’re less complex. By design, they require fewer moving parts. Depending on what you use your vehicle for, a solid axle might work just fine.