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M12 extension housing oil leak

ATF transmission oil (red color) accumulating between the transmission body and the extension housing. This is where the 5th, 6th and reverse gears are located. This is caused by a failed RTV seal, and the only way to repair this is by removing the extension housing and resealing the flanges. The failed factory RTV sealant. The earlier effort to seal the leak from the outside was only a partial success, but who wants to remove the transmission only to repair this leak? The magnets trap metallic particles produced as the transmission wear (or fail), which would otherwise be circulating in the oil and cause further wear. I wanted to remove the magnets to clean out all the particles, but I had to use more than sensible force, so I cleaned them in place. I found no large particles or shavings, only fine metallic dust that disappeared into the cleaning cloth.  A good sign. Another source of oil leaks are the inner and outer rear seals of the extension housing, so I changed these too. If you

Torque tube maintenance

I had to purchase a heavy duty circlip plier (Knipex 4811-J4, 320 mm) to remove the large circlip fixing the drive shaft in the torque tube. Inside, there was nothing to tell that this torque tube had been in service for 20 years and 110k miles. The rubber couplers looked and felt like new. There was no play in the bearings, but they had less preload and made more noise than their new counterparts* A curiosity is the "16/1/2004" date stamp on the drive shaft for a car produced and sold in 2003 (The black marks are from my oily fingers). To remove the rubber couplers the bolts have to be heated with a blow torch to break the factory thread lock. I initially tried without heating the bolts, which quickly broke the bits. Heating the bolts caused the rubber couplers to catch fire, so this method renders the couplers U/S. The torque tube rebuild kit includes new circlips, O-rings and bearings, and also the slinger. A hydraulic press is required to replace the parts. Not much force

Spec stage 2 clutch kit

Lightweight aluminium flywheel with steel insert Worn slave cylinder At 110k miles (178 000 km), the car had developed the "clutch pedal stuck to floor"  issue when shifting at high RPMs. This is caused by a worn slave cylinder, where worn seals allows dust to enter the circuit and cause the slave cylinder to get stuck by the high inertial forces and the increased friction. A sure sign of this happening is that the clutch fluid gets discolored again quickly after a change. State of stock clutch The OEM clutch from LUK is more than capable of handling the LS6 stock power. The car still had the stock clutch, which was in a surprisingly good state for the milage. Minimal surface wear and only a few small hotspots, one could even mistake the clutch disk for a new item.  However, with everything else disassembled, it would be dumb not to replace the clutch now, as it will probably not last another 20 years. Guess what happens when a flywheel, a pressure plate and a clutch disk bou

Built 4.10 rear differerential

Late April, and the spring finally arrived with temperatures making it possible to start on the pending repairs.   This is what the T-1000 Terminator is made of; liquid metal drained from a Getrag differential. A magnet picked up a lot of metal shavings.  The output shafts have significant play, which is an indication of worn clutch packs and belleville washers, and possibly broken output shaft stubs (I will find out when I disassemble the differential later). With all these issues, this differential needs a complete rebuild. It is hard to find specialists with the knowledge and the tools required to perform this work in Norway. The cost of shipping the differential to the USA and back for a rebuild is also excessive, due to the weight. Built 4.10 differential C6 Z06 output stub shafts C7 Z06 clutch packs Motive 4.10 ratio ring and pinion gear New bearings, carriers and seals To ensure that history does not repeat itself, I'm not on a track day again until a differential oil cooler

Replace pilot bearing

I decided to install a new pilot bearing together with the new clutch kit. Notice that the tip of the propeller shaft, which is supported by the pilot bearing, has turned blue. This is an oxide layer forming on steel heated above 205 °C (401 °F), indicating that the pilot bearing has worn and heated up due to high friction. The surface is perfectly smooth and runout is within specification, so I'm reusing the propeller shaft. A bearing puller is required to remove the pilot bearing. It is necessary to totally mangle the bearing, as the tool does not get a good grip on the outer bearing race. The internal bearing race is crushed and the steel rollers drop out (beware!), at this point the bearing puller can be reinstalled so that it grips the outer bearing race from the top. It took a few attempts to get a good grip, and then it finally came out. New bearing installed. Notice that the chamfered side is out, this side also has an O-ring to protect the needle bearings from contaminatio

Replace rear engine seals

I've previously replaced the front engine seals, the oil pressure sender, cam sensor and the oil pan gasket, but oil was still collecting at the back of the oil pan. I think I've identified the source. The seal lip has hardened and worn down. Signs of a worn seal is visible on the surface of the crankshaft, but it felt perfectly smooth. I'll locate the new seal further in, as the rear cover is designed to allow this. While it was accessible I also installed a new oil gallery barbell, which is supposed to increase oil flow and reduce the amount of unfiltered oil bypassing the barbell - and thereby the oil filter. I drilled a small hole in the OEM barbell and used a wood screw to pull it out. New barbell in place. It has a threaded hole, making it easier to remove if one should ever need that. I managed to sneak the mobile phone camera up to the cam sensor, hiding in a chamber on the top of the engine (used for a distributor on earlier generations of the engine) and right abo

Removing and reinstalling the drivetrain

Removal Removing the differential, gearbox and torque tube was not as difficult as I was lead to believe. I used a jack for the engine, a jack for the torque tube and a transmission jack for the rear subframe and differential. The torque tube slid out of the bellhousing easily, and I had adjusted the rear transmission jack so that it kept the whole assembly in balance as I removed it from under the car. I forgot the fact that the rear subframe  is attached to this assembly only by one single point - the differential mount. It is only a piece of rubber with 4 posts sticking out of it, so it was bent at close to 45 degrees. I need a new differential mount, fortunately I had a replacement ready. I disconnected the rear brake lines and removed them, as I found it stupid to bend brake lines this much to get past the drive shafts. I will reroute the brake lines before reassembly. I see no logical reason for the brake lines to run down and behind the rear differential, when they can simply be

Flexible seat belt receiver for racing seat

The previous owner has installed a nice Sparco Evo 2 racing seat, but I don't like how the seat belt receiver is mounted to the seat bracket. The receiver is too high up on the waist, in an impact the driver can slide under the belt and or get  fatal abdominal injuries. After some Googling, I found a flexible seat belt receiver on GM Parts Giant for only $5.80, made for the rear seats of a Buick Envision. GM part number 84690213. The Corvette clip is slightly wider than the clip out of a sedan, so the Buick receiver has to be slightly modified. I'm used to this in European cars, where the clip and receiver is coded to each other, e.g. making it impossible to install the rear left or right passenger clip in the center receiver. 30 seconds with a Dremel carbide cutter and the issue is resolved. The flexible seat belt receiver is now routed through the side of the seat, in a far better and safer position for the driver.