Using a twin stick on the D300 gives you a shifter for each output shaft. A couple of the things this allows is the use of 2wd (RWD) Low for crawling over hi-traction areas like slickrock, and FWD Low for doing front digs. To prevent the possibility of putting one output into Hi and the other into Low, there are 2 interlock pills in the front output bearing housing. A side effect of this is that the pills also prevent the use of FWD Hi range. Some people remove the pills entirely, but you risk blowing the case up. Getting one output into Hi and the other into Low will bind the t-case internally and something will give. Either the gears, bearings or the case itself.
This notch in the rear shift rail needs to be extended forward as shown. Notch extended with an
[COLOR=#009600 ! important][COLOR=#009600 ! important]angle [COLOR=#009600 ! important]grinder[/COLOR][/COLOR][/COLOR] and a well-used (rounded edge) grinding
[COLOR=#009600 ! important][COLOR=#009600 ! important]wheel[/COLOR][/COLOR]. You can, however, do a little bit of grinding on the rear shift rail that will allow FWD Hi range while still preventing the possibility of binding up the case. But why? Well, if you're just running the D300 alone, then it probably won't do a whole lot for you. But, suppose you're running a crawler box with it's reduction engaged and the D300 in Hi. Normally, you can't just pull the rear output into Neutral to do a front dig. You need to do some more shifting, putting the D300 into FWD low, maybe disengaging the crawler box and/or picking a gearing that is less than optimal to do the dig. With this mod, you can just slip the rear output into Neutral and pound away.
To perform the mod, you need to remove the rear shift rail from the case and front output bearing retainer. That task is beyond the scope of this article, but is done as part of a rebuild of the case. To allow FWD Hi, the back notch in the rail for the back lockout pill needs to be extended forward.
Another view of the new, extended notch in the rear shift rail. The notch is about .42" long. The distance between the two shift indents (Hi and Neutral) next to it is about .42" as well, so the new length of the notch needs to be about .84". In
[COLOR=#009600 ! important][COLOR=#009600 ! important]4wd[/COLOR][/COLOR]
HI (levers full back, rails full forward), this notch extension allows the rear shift rail to move back and reach the Neutral position before the pill stops the rail from going any further.
To extend the notch, I used a 4.5" angle grinder with a well-used grinding wheel in it. The worn wheel has a nice, rounded leading edge instead of the sharp corner of a new
[COLOR=#009600 ! important][COLOR=#009600 ! important]wheel[/COLOR][/COLOR], and it worked well for shaping the "ramp" at the new front of the notch. Just go slow, and stop frequently to check your angle, depth, etc. You don't need precision in the thousandth's here. You can easily eyeball it as you go and be plenty accurate.
Check the new length of the notch frequently and stop once you get to about .84" and you're done. Re-install the rail and you'll now have FWD Hi capability and still be re-assured that you cannot shift one rail into Hi while the other is in Low.
