Below is my constantly improving Subaru Justy project list. It is a 1989 Subaru with a 1.2L 3-cylinder with four wheel drive by way of a locking center that enables it to go from front wheel drive only to sending power to all 4 wheels by essentially locking the front and rear driveshafts together.
11/2016
Problem: Justy Is 2wd mainly with push button 4wd that cannot be used of high traction surfaces due to drive-train binding cause by the front and rear axle needing to spin at different rate while in a turn.
Solution: Is a current project in which I am trying to install a viscous coupling inline with the prop shaft to the rear, allowing me to leave the factory vacuum actuated 4wd engaged full time, and allowing speed differentiation via the viscous coupling. This will allow some power to always be transferred to the rear axle, the more front wheel slip happens the more power the coupling with send to the rear due to the silicon based shear thickening fluid found inside, this will aid in low traction driving situations such as on snow or ice. The only down fall with the viscous coupling approach is that unlike locked 4wd, it will not allow 100% torque transfer to the rear if the situation required it. My hope is to overcome this issue by making dog engagement style cogs, one will be mated to the outside of the viscous coupling which spins with the input shaft, the other will slide along the output shaft, when disengaged will allow the coupling to differentiate speeds as intended. However, when the dogs are engaged it will physically mate the input shaft to the output shaft and force the rear axle to spin at the same rate as the front. This way if there is no available traction at the front 4wd can be engaged and all the power will be available to both the front and rear axles as necessary.
10/2016
