i just was experimenting in my garage while my VH is being worked on, and seen this on frsport...
i have the Z1 motorsports short shifter, and a shifter relocation plate that shortens the shift rod, and its pretty clicky already, but i wanted to see how retarted it could get...
I went and pulled the return spring nuts off each side of the shifter (27mm) and there is a small spring inside that goes over the plunger. its large enough that you can fit a smaller spring inside. I had some springs left over in a huge "family pack" of misc springs that i got from home depot a while ago..
inside this kit there are 2 springs which are about 1/8" diameter x 1" long, and fit around the plunger shaft extremely tight. they are pretty tough to compress, and are about 1/4" too long to allow for full shifting compression. i dremmeled it down to length and popped it on the shaft. tossed the OEM spring on over that and re-screwed everything back together.
initial impressions while its sitting on the garage is about a 30% increase in resistance when going from left to right with the shfiter. i personally like the feel more so than a lighter shifter movement. shifting left into 1st had the nice resistance. shifting 1>2 is normal/stock, 2>3 felt slightly more "assisted" than stock due to the increased spring pressure. and of course 3>4 was normal/stock. 4>5 had the additional 30% resistance, but i like the added feel.
install on the garage floor took about 30 seconds per side, in the car.... lets just say the z32 transmission is a super tight fit in an S13 with a VH. i cant compare to an actual Z32 transmission tunnel.
you should be able to do this in car, minimal transmission fluid may be lost. it should be pretty good and sealed, but my fingers got a little wet screwing around with the plunger.
felt good to save $50.00 and get the same effect...