JezzaH6 wrote:Shifter Shaft Seal Failure
Accelerating hard from the traffic lights and shifting quickly from first to second got me a nice strong burning gear oil smell (this happened at a similar time to the oil line failure- no idea why the car decided that month was the month it didn't want to hold fluids anymore)!
Thankfully this occurred not far from home, and a quick inspection showed only a small amount of gear oil leaked onto the hot exhaust. Limping the car home and getting underneath it showed the rubber section of the shifter shaft seal was torn, and on hard acceleration the gear oil sloshing to the back of the gearbox would leak out and splash onto the exhaust.
A replacement seal didn’t take long to arrive, and with the car up as high as possible on axle stands the work could begin. The gearbox undertray, exhaust, heat shield, tail shaft, gearbox support and shifter linkage all had to be removed just to give me a closer look. While people online stated the seal is removable with the gearbox in the car, I couldn’t find a way that I was confident wouldn’t scratch the sealing surface or damage the shifter shaft.
I ended up pulling the rear casing off the gearbox, which meant I was able to correctly press out the old seal, as well as inspect the internal condition. It also let me have a look at the centre diff- as this is a DCCD unit I was definitely keen to see what it looked like (even if it was ultimately pretty unimpressive looking)!
The shaft seal replacement was uneventful, but what was really annoying was trying to get all the internal oil trays lined up again. The stock gearbox used an oil pump, but the replacement gearbox relies on splash lubrication, so getting these trays lined up was critical. Trying to hold these in place, as well as correctly routing the DCCD wiring and holding the split shaft bearings in place was difficult, and ended up taking many attempts. I found a trick using petroleum jelly to hold it together; testing this in a gear oil sample showed it dissolved completely with no signs of incomplete mixing.
Eventually it all came together, and with the sealant dry everything else could be reassembled and the gearbox filled with oil. This seems to have fixed the problem, and the back of the gearbox has remained dry since.
While everything was apart anyway I took the opportunity to rebuild the shifter linkage. I have replaced the bushings in the past, but had noticed these were already showing signs of wear, so I had another set waiting for the next time I was in there. I had never removed the lower shifter pivot, however, and the grease in that was pretty crusty. The pivot cup hold-down has an o-ring in it for some compliance which was quite crushed- replacing the grease and the o-ring, as well as the new shifter bushes, has really improved the shifter feel.
I haven’t seen too many examples of this seal failing, and I am not sure why this one decided to. The kms are relatively low for the age of the box, so potentially it had sat for a while, but since installing it has done numerous track days and lots of other driving with no signs of failure. Who knows.
Wow and kudos for ruling your mechanical “setbacks”, or as I refer to my own: mechanical “opportunities”
The post is serendipitous for me as I need to do all the gearbox linkage knuckles and bushes, and I’m not sure what I’ll find with the audm my07 STi shift knuckle double roll pins. There’s an awesome Corgiwerks post I’ll dig up for context.
But the point being, it’s potentially good practice to replace this seal when doing a major overhaul and clutch job?
If the box was fully dropped then removing the rear section might be unnecessary?
