It turns out, it was closer to three years since I last had something to post. In the meantime we managed to build a house and move in so now I finally have a proper garage! I guess the garage is not much in the eyes of you Americans but it's damn huge by European standards! The last three years we've lived in a tiny flat to cut on the expenses while building the house and the garage I had rented at that time was even smaller than the original one and with no electricity. Well, now I also have an 1985 Land Rover in the driveway, the only problem with it is that it's not mine... Still, it's such a cool car. A friend wants to sell it and lets me use it until he finds the buyer because he doesn't have the space for it.
It's beautiful here. It's not in the mountains, it's lowlands but there are a lot of hills and valleys around here. The video game Kingdom Come Deliverance takes place in this area - the game map, which is very accurate, is set in the area only about 10km east from my house.
(This picture was actually shot from the children's room window)
I've finally had some time the last two weeks to work on the S12 again and I managed to fix a few issues that bothered me. Fixed an exhaust rattle, then fixed an audible clunk coming from the drivetrain, turned out that was just because of loose half shaft bolts and then I adjusted the camber and drive height in the front. The car drives great now!
Now to the more interesting topic: I've been messing with the gearbox because what bothers me the most while driving the car is how shifting between the gears feels like. The gear lever doesn't come all the way back to the center from the left side between 1st and 2nd gear. It snaps back to center from the right side between 5th and Revers just fine but from the left side it just goes half way. When shifting fast from 2nd to 3rd, for example while on the track, I have to concentrate on moving the lever from the left position to the center before putting it up in the 3rd, otherwise I hit the "wall" between 1st and 3rd gear which is really annoying and also a little bit scary because you really don't want to downshift to 1st by an accident.
The whole problem is in the design of the 71b gearbox. As I thought about the issue, I figured the easiest way to fix this is to swap the 71b for the 71c out of a mk2 S12 or an S13 which has the shifting mechanism completely redesigned. Well, I Have not done that.... Instead, I have bought a second 71b gearbox to experiment with and learned to use Autocad 3D software to redesign the faulty part, took me quite a lot of time too, it's a pretty complex part. I had the part made by a machinist, he did a great job but I still had to work on it with a file and sand paper for half a day to make it work well - it's a prototype after all. This is what I ended up with:
top - original part ; bottom - new design
left - new design ; right - original part
left - new design ; right - original part
The most important difference from the original design is the change of the profile cut in the front cylindrical part as seen in the last two pictures. The way the mechanism works is that there is spring loaded plunger pressing against this profile. When the gear lever is in the center the plunger sits in the center of the profile and when you move the lever right or left the whole part turns alnog it's axis and it forces the plunger up the cut slope working against the spring pressure which in turn wants to return the lever back to the center. The original Nissan design of that profile is not symmetrical and my problem with that is that the slope the plunger works against when moving the lever left to 1st or 2nd gear is a lot less steep than the right side where the 5th and Reverse is. I redesigned the profile to be symmetrical and steeper so the lever will snap back to center from left position just as well as from the right position.
Another change, and that was just a bonus, is that I moved the hole where the gear lever is connected by 10mm up and thus moving the fulcrum point which results in shorter shift track - It's now a short shifter as well! For this to work right I had to modify the gear lever itself - the lower part of the lever, where the plastic bushing sits, had to be made the 10mm longer. While I was at it I also put more of a bend in the lever itself to place the shift knob a little closer to the driver.
left - original part ; right - new design
Sadly I have not had the chance to fit it in the car and test it on the road but it seems to work as intended with the spare gearbox on the bench. I have not road tested i because you need to take off the gearbox housing to install the part so that means pulling the gearbox from the car and that is annoying. When I pull the gearbox from the car I plan to have it refurbished because one of the bearings inside is whining and I don't have the money for that right now... Anyway, this is how it all goes together:
The next thing on the list is upgrading the cooling setup. I just got this ebay radiator with aluminium shroud and couple of fans.
And I also got pair of these funny wire headlight protectors that came on the cars with headlight wipers. Even without the wipers, they look so cool on the car, very rallye style.
Damn, it feels nice to be back!
