Join Date: Apr 2010
Location: Phoenix, AZ
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The stock front diff is open. There isn't even a option from the factory for a front limited slip. (Jeep is the only manufacture I know that even has a front TAD option.) If you want a limited slip for the front the best choice is the Detroit True Trac from Eaton. It is a gear driven proportioning diff so other than slightly increased centering of the wheel in 4wd it is completely transparent in the front.
The Stock rear limited slip in the newer trucks (I think is start in 04) is a gear driven torque sensing unit. The problem with the unit is it isn't a very high bias unit and only provides about 2:1 torque ratio. Compare this to a True Trac that has 3.5:1 ratio. The way the gear driven units work is by multiplying the torque available to the low traction wheel to the high traction wheel. So for the stock AAM unit this results in the high traction side having 2x the drive of the low traction side. Problem is in Ice, 2x of zero is still zero and nothing happens. You can overcome the lack of traction on the low traction side by spinning the wheel or by applying emergency brake (recommended method). The emergency brake provides torque for the multiplier to multiply and gives you drive on the high traction side.
The older clutch type units used a fixed bias ratio where it takes a certain amount of torque to cause the axles to spin at a different speed. This is why under light throttle and zero torque on one wheel they will still pull you off; however, if you over come the fixed bias they will break free and spin also. You can use the same emergency brake trick to help them when one wheel has 0 traction.
The torsen type units have an advantage in that they drive more like a open diff so they are more transparent while still providing good traction improvement. Also, since they are gear driven they don't wear nearly as quick; however, most cannot be rebuilt if they do wear out.
Full lockers are a different setup completely. They keep both wheel locked together unless one wheel is driven faster by turning. With a full locker the slower turning wheel will always have the power (deceleration is the opposite) since they unlock by having the faster turning wheel being unloaded by the ground. The full locker has three modes, left wheel over driven, right wheel over driven or locked. The over driven wheels provide no power to the ground.
Leonard Pennock AD7AS
2006 Ram 3500 4x4 6sp, F&R TrueTrac, EFI Live, GT3782R, Dual Disc
2008 Ram 5500 4x4, ATS7500/VGT, 2xCP3