Even when applying much more pressure it was difficult to get the Kartboy bushings to deflect very much. These are much stouter than the tired and flexible old rubber that it replaced.
Again, installation is simple and straightforward. With the transmission cross member removed, simply unbolt the sandwich plate that holds the old bushings to the cross member and then reinstall with the polyurethane bushings. Easy.
The factory supplied transmission mount is a pretty hollow mount made of the same soft rubber as the transmission bushings. While I’m sure this does a great job absorbing some vibrations and reducing noise in the drivetrain, it is super soft and flexible which allows the transmission to squirm around.
Luckily, this Group N transmission mount from STi was collecting dust in the corner of the garage. Don’t let the cobwebs and dirt fool you, although this mount is built like the stock piece using bonded rubber sandwiched between some steel brackets, it is much more solid with a tough rubber that is significantly stiffer than what is in the old factory mount. This should do well to reduce drivetrain movement during hard acceleration and cornering without adding too much NVH.
With our drivetrain now shored up to handle some power and the transmission back in the car, the last thing to do is to fill up with some fluids. Our friends over at GrimmSpeed tipped us off to this transmission fluid cocktail composed of Castrol Hypoy C, Pennzoil Syncromesh, and Redline Lightweight Shockproof (note, the beer is not part of the cocktail). This magic mixture of smelly viscous goo should help our transmission keep spinning and shifting smoothly for some time to come.
All four of the bottles will be too much to fill the transmission, so add one bottle of the Castrol, then the Redline, Pennzoil, and finally top it off with half of the other bottle of Castrol. Make sure to use a funnel and fill slowly so you don’t end up with a puddle of Shockproof on your garage floor.
With the drivetrain sufficiently strengthened, we can move on to the fuel system in our next installment.
Its been about 1,000 miles since everything has been installed on the car. Initially, the clutch pedal return was much more forceful, the clutch would have a foul burning smell if you tried to slip it all, and there was horrible chatter and vibration from a start and under deceleration. But now that everything has been broken-in appropriately its all very smooth. Pedal return is still quick, but that’s to be expected with an upgraded pressure plate. The burning smell is all gone and chatter has been reduced to a minimum. All in all, everything drives and feels nearly how it did from stock but is capable of handling much more power, which is exactly what we were hoping to achieve. Now that our drivetrain is refreshed and bolstered to hold up against the higher power levels we can focus on getting our fuel system up to task before we kick the factory supplied hair dryer to the curb.