Green viper 1
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Can someone explain the differences in the gen3 rear differential and a gen 4
Gen3 and gen 4 rear end
- Thread starter Green viper 1
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steve911
Enthusiast
Gen 3 has the hydro loc and has questionable longevity. The Gen 4 has the GNK much better. If you find a Gen 4 diff make sure it has the stub axles in it as the Gen 3 ones will not fit. Both diffs will work in any '03-'10 car. Oh, by the way both have been dicontinued by Dodge.
I got this from UNITRAX web site.
Dana Spicer Hydra-Lok
Dana’s Hydra-Lok was originally developed by ASHA Corporation in Santa Barbara, California. McLaren Performance acquired ASHA and sold the rights of ASHA’s Gerodisc technology to Dana’s Spicer light duty axle division. Dana completed development of the unit and trademarked the LSD as the Hydra-Lok. Production began in Syracuse Indiana and in 1999, Jeep debuted the Hydra-Lok in the Grand Cherokee.
Gerodisc technology is speed and torque sensitive, operates full-time, and offers proportional torque transfer with progressive action. It uses the differential oil to operate the Gerotor. TwinDiscs provide one coupling per wheel. The fluid is released at calibrated pressures to engage the clutch pack.
The Hydra-Lok transfers wheel torque as conditions demand, ensuring improved traction and handling. Unlike traditional disc-based LSD’s, the Hydra-Lok offers controlled torque transfer. It does not waste power on wheel spin, rather it transfers torque to the wheel with the most traction. The torque is independent of the slipping wheel condition. The Hydra-Lok is speed-sensing meaning that the torque transfer is independent of the slipping wheel’s traction. The amount of torque transferred to the wheel with traction is based on the speed of the spinning wheel. Resulting in nearly immediate transfer of torque from the wheels that slip to those that grip.
According to Dana Corporation, when a Hydra-Lok equipped Viper begins to negotiate a curve, the vehicle reacts as if it had an open differential to reduce the potential of over-steer. As the vehicle continues through the corner, it takes on the characteristics of a limited-slip differential, transferring torque to the wheel with traction. Coming out of the curve, however, the Hydra-Lok allows the Viper to deliver the maximum amount of torque to the ground for improved speed while exiting.
The 2003 version of the Hydra-Lok had an issue with cross pins failures. UNITRAX developed a replacement 300m cross pin to help prevent Hydra-Lok failures. In 2004, Dana upgraded the Hydra-Lok with a heat-treated cross pin. However, side gear and pinion gear failures have continued to plague Gen III SRT 10 owners.
Unfortunately, dependability and durability issues have spoiled the promise of the M44-4 Hydra-Lok. We will now examine the alternatives to the Hydra-Lok.
GKN Visco-Lok
The 2008 through 2010 “Gen IV” Viper SRT 10 is equipped with the GKN Visco-Lok. The Visco-Lok has been in production since 1999 and is a standard feature in the BMW M3.
The Visco-Lok is a unique hermetically sealed speed-sensing limited-slip differential. The unit benefits through its high-torque progressive locking characteristics which provides maximum torque transfer in excess of skid torque.
The Visco-Lok operates through a self-contained silicone-fluid filled reservoir and shear pump that actuates a wet friction clutch pack. The pump generates pressure proportional to the speed difference between the wheels. The clutch pack actuates thereby transmitting torque to the appropriate wheel. The locking effect increases with the speed difference across the drive wheels.
This locking characteristic enables the Viper to accelerate well on surfaces with different friction conditions between the drive wheels. Additionally, GKN states that the Visco-Lok allows even better acceleration and less under-steer in cornering than compared to torque-sensing LSDs.
UNITRAX has installed many Visco-Lok LSD’s in Gen III SRT 10 Vipers, giving the SRT owner improved limited-slip performance and in our opinion a substantial upgrade over the Dana Spicer Hydra-Lok. The Visco-Loks have proven to be especially reliable in stock or modestly upgraded Vipers.
Dana Spicer Hydra-Lok
Dana’s Hydra-Lok was originally developed by ASHA Corporation in Santa Barbara, California. McLaren Performance acquired ASHA and sold the rights of ASHA’s Gerodisc technology to Dana’s Spicer light duty axle division. Dana completed development of the unit and trademarked the LSD as the Hydra-Lok. Production began in Syracuse Indiana and in 1999, Jeep debuted the Hydra-Lok in the Grand Cherokee.
Gerodisc technology is speed and torque sensitive, operates full-time, and offers proportional torque transfer with progressive action. It uses the differential oil to operate the Gerotor. TwinDiscs provide one coupling per wheel. The fluid is released at calibrated pressures to engage the clutch pack.
The Hydra-Lok transfers wheel torque as conditions demand, ensuring improved traction and handling. Unlike traditional disc-based LSD’s, the Hydra-Lok offers controlled torque transfer. It does not waste power on wheel spin, rather it transfers torque to the wheel with the most traction. The torque is independent of the slipping wheel condition. The Hydra-Lok is speed-sensing meaning that the torque transfer is independent of the slipping wheel’s traction. The amount of torque transferred to the wheel with traction is based on the speed of the spinning wheel. Resulting in nearly immediate transfer of torque from the wheels that slip to those that grip.
According to Dana Corporation, when a Hydra-Lok equipped Viper begins to negotiate a curve, the vehicle reacts as if it had an open differential to reduce the potential of over-steer. As the vehicle continues through the corner, it takes on the characteristics of a limited-slip differential, transferring torque to the wheel with traction. Coming out of the curve, however, the Hydra-Lok allows the Viper to deliver the maximum amount of torque to the ground for improved speed while exiting.
The 2003 version of the Hydra-Lok had an issue with cross pins failures. UNITRAX developed a replacement 300m cross pin to help prevent Hydra-Lok failures. In 2004, Dana upgraded the Hydra-Lok with a heat-treated cross pin. However, side gear and pinion gear failures have continued to plague Gen III SRT 10 owners.
Unfortunately, dependability and durability issues have spoiled the promise of the M44-4 Hydra-Lok. We will now examine the alternatives to the Hydra-Lok.
GKN Visco-Lok
The 2008 through 2010 “Gen IV” Viper SRT 10 is equipped with the GKN Visco-Lok. The Visco-Lok has been in production since 1999 and is a standard feature in the BMW M3.
The Visco-Lok is a unique hermetically sealed speed-sensing limited-slip differential. The unit benefits through its high-torque progressive locking characteristics which provides maximum torque transfer in excess of skid torque.
The Visco-Lok operates through a self-contained silicone-fluid filled reservoir and shear pump that actuates a wet friction clutch pack. The pump generates pressure proportional to the speed difference between the wheels. The clutch pack actuates thereby transmitting torque to the appropriate wheel. The locking effect increases with the speed difference across the drive wheels.
This locking characteristic enables the Viper to accelerate well on surfaces with different friction conditions between the drive wheels. Additionally, GKN states that the Visco-Lok allows even better acceleration and less under-steer in cornering than compared to torque-sensing LSDs.
UNITRAX has installed many Visco-Lok LSD’s in Gen III SRT 10 Vipers, giving the SRT owner improved limited-slip performance and in our opinion a substantial upgrade over the Dana Spicer Hydra-Lok. The Visco-Loks have proven to be especially reliable in stock or modestly upgraded Vipers.
Really? Did they change it up for the gen 5 again? I thought they were still using the gen 4 setup. I know the ratio changed, but didn't remember reading anything about a locking unit changing.
steve911
Enthusiast
I have a new Gen V diff in my hands. The bat wing (rear cover) is different, The stub axles will require the new Gen V half shafts (very pricey). It does have the Gen 4 GKN diff and of course the 3.55 gear set.
Ah, guess I can understand how they could discontinue the old stuff then. They still use some of the same parts, but not the whole unit and they don't sell the piece parts. Makes sense to some degree.
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