I swapped in a earlier D1 front housing into my 02 D2. In my case, there is wiring for 2 switches that tell the SLABS low range is engaged. The D1 housing only had one switch on top and just in front of the lockout solenoid. There was no switch in the housing just in front of the low range shift assembly (it would face forward on a horizonal angle). I had to wire in a switch which I mounted in the dash for this purpose. Without that switch the hill descent would not work. The low range/diff lock functioned normally since it's all mechanical anyhow.