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Finally back on the road! 😁

In August 2022, I returned home from a track day event with a broken differential and cracked rear brake rotors. I already knew that the differential was overdue, as it there was a high buildup of metallic particles in the differential fluid. With a mileage of 170.000 km (106k miles), I decided it was time to replace all other parts accessible after removing the torque tube, transmission and differential. From August 2022 to April 2024, time was spent to disassemble the drivetrain, saving up money for parts, waiting for parts to arrive and doing the actual work: Removing the drivetrain Larger 330 mm rear brakes from C6 Z51 New built 4.10 differential with C6 Z06 internals Rear engine seals, gaskets and barbell replacement Pilot bearing replacement Spec Stage 2 clutch kit with aluminium flywheel Torque tube maintenance M12 transmission extension housing oil leak Shorter rear brake lines Slave cylinder shimming and Hinson remote bleeder C6 tunnel plate upgrade Reinstalling the drivetrain

Fluid refill station

Refilling the transmission and differential fluid can be a mess. I made this "station" with an electric pump, battery and a fluid container mounted on a plate with weels, which can be easily moved into position under the car. I'll add a push button for running the pump later on.

C6 tunnel plate upgrade

The tunnel plate was initially designed as a heat barrier between the exhaust and the torque tube, but the GM engineers discovered that a thicker plate reduced the torsional flex in the chassis, which was then used in the C5R race cars. With the tunnel plate already removed for servicing the drivetrain, this was a nice opportunity to upgrade the tunnel plate in my C5Z. The Elite Engineering and TPS Motorsport tunnel plates became all too expensive when adding overseas shipment, so I sourced a used C6 tunnel plate. Except for the increased thickness, the C5 and C6 plates are geometrically indentical, so upgrading to the C6 tunnel plate is plug & play. The C5 tunnel plate is an 1.6 mm sheet metal plate.With the introduction of the C6, the tunnel plate thickness was increased from 1.6 to 3.2 mm. The torsional rigidity of  aluminum increases with increasing thickness. This is because thicker materials have a larger cross-sectional area, which results in a greater resistance to torsion.

Monitoring critical engine data

  The stock head unit is removed and replaced with a small single board amplifier. I used the free space to mount a 8 inch tablet running Microsoft Windows. By using a HP Tuners OBDII-adapter and the VCM Scanner application, I can monitor engine data which is critical during track days. The gauges turn red when any values are below/above defined thresholds, e.g. oil temperature above 130°C (266°F) or oil pressure below 20 psi, so only a quick glance can give an overview of the status.

Dorman 03133 exhaust manifold flange hardware

One of the exhaust manifold flanges had a broken stud. I found that the Dorman 03133 kit with studs and nuts fits the C5 Corvette nicely.

Transmission fluid temperature in the DIC

Did you know that the Z06 has a differential fluid temperature sensor that allows you to read the temperature in the DIC*/LCD display)? The reading is not available by default, but is added to the DIC after a "high trans temp" warning, which is activated when the transmission temperature exceeds 130°C (266°F) for more than 10 minutes. The trans fluid value can then be selected for viewing in the DIC similar to oil and coolant temperature. The sensor is a part of the the fluid fill plug in the T56 transmission.  The high thresholds are also why most owners have never seen the warning, as it will hardly ever happen during normal use. During continous heavy load on track days or circuit racing, the warning thresholds are actually too high. The fluid temperature can raise far beyond 130°C before the driver is notified, due to the 10 minute delay. Above 130°C, gear oils starts to break down and lose its viscosity. This can create a viscious circle of increasing friction and temper

Fuel pump not priming

Having reinstalled the drivetrain, I wanted to start the engine to check for any issues. It fired up once, then died after a few seconds and would not start again. I noticed that the fuel pump was not priming when I turned on the ignition, the fuel pressure meter I've installed on the fuel rail also confirmed zero fuel pressure. Additionaly, the starter motor did not turn over, all I got was a blackout of all lighting when I turned the key. I erased a long list of fault codes, removed the fuel pump relay and jumped the 12V supply, but the fuel pump would not run. I started thinking of possible causes; fuel pump faulty due to car being stationary for a whole year, clogged fuel filter, wiring passing over torque tube damaged on removal or reinstall of torque tube. Oh no... removing all of the drivetrain again?! A new $250 fuel pump assembly?! A web search for "c5 corvette fuel pump not priming" gave multiple hits on  corvetteforum.com , and in one of the threads the ground

Winter is coming...

Before I could finish the Corvette the winter returned with freezing temperatures, and I do not have any desire to crawl around on the garage floor in these conditions. I'm anyway too late for a test drive, with snow, ice, mud and road salt on the roads.

Reinstalling the drivetrain

"Assemble in reverse" New rear engine seals and gaskets, new flywheel, new clutch, new slave cylinder, rebuilt torque tube, transmission leaks fixed. The drivetrain is finally ready for reinstall.  I decided to reinstall the drivetrain in three steps. This makes it easier to get the clutch splines and the torque tube lined up correctly, as there is less mass to move around:  1) Torque tube  2) Transmission and differential  3) Rear subframe with suspension Again, the bellhousing bolts caused troubles, with no space for my hands or any socket tools to get the threads engaged. The solution I came up with was to loop a wire around the bolts, which I could use to guide the bolts in place. Transmission and differential assembled and ready to be mounted to the torque tube.  By using only hand force to install the torque tube, there is less chance of damaging the pilor bearing. I stretched out under the car and lifted the torque tube up by hand, and then slid it in place. If any mo

Skip shift solenoid delete

A skip shift eliminator  has made the skip shift solenoid itself obsolete. The previous owner had cut off and blanked the electrical connector, but that did not stop oil seeping through. While the solenoid was accessible, I decided to replace it with a simple plug. The skip shift solenoid thread is M20x1.5, which happens to be the same size as a Subaru EJ oil drain plug. Unfortunately a bit too short, but I solved that by some DIY machining, allowing the bolt to seat on the chamfered edge in the transmission. I also applied a thread sealant. Disable skip shift in ECM Instead of a skip shift eliminator, the skip shift can be disabled in the ECM using HP Ttuners. By setting "Disable TPS" to 0%, the skip shift is effectively disabled. This also stops the "1 TO 4 SHIFT" indicator in the speedometer from lighting up. What is skip shift/CAGS? CAGS is short for computer aided gear selection. Shift blocking or “skip shift” is a feature of six-speed manual transmissions adde

Slave cylinder shimming and Hinson remote bleeder

  I installed a Hinson remote clutch bleeder line, which makes it easy to bleed the clutch line later. Ideally, the bleeder should have used the stock design with a tapered fitting, instead of a crushed washer. To avoid leaks, I used Loctite Form-A-Gasket on the threads and washer, and then secured the line to the fitting using threadlocker. I measured the A and B dimensions as illustrated above, with A-B = 3.7 mm (0.146") which is within the  3.18 - 5.08 mm (0.125"-0.200") clearance required for bearing travel and clutch wear, so I did not have to shim the slave cylinder. Avoiding the shim also maintains the self centering of the slave cylinder on the torque tube / input shaft, so I was happy that a shim was not required.

Rerouted and shorter rear brake lines

The stock routing of the rear brake lines looks completely illogical (probably due to factory assembly procedures). The brake lines run from above the transmission, down to the rear of the differential and then back again across the rear subframe.  By rerouting the brake lines, the driveline can later be removed without considering the brake lines. My plan was to straighten and reuse the original brake lines, but my flare kit quickly failed as it couldn't handle the hard steel. I can't spend a fortune on a tool I'll use once, so with "Made in China" I switched to nickel copper brake lines, which are softer and easier to form. To make the correct bubble flares, I used this method:  Make a Bubble Flare with a Double Flare Kit New shorter brake lines in place. I used a steel wire to make a template for bending and cutting the new brake lines. This works for both sides, but the length of the top section depends on how you bend the brake lines in the car (click on the

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 leak is caused by a failed RTV seal between the two housings, 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 bottom/outside was only a partial success, but who wants to remove the transmission only to stop this leak? The magnets trap metallic particles produced as the transmission wears, 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

Torque tube maintenance

To pull the driveshaft out of the torque tube a large  ~ Ø110 mm circlip has to be removed. I tried using a regular circlip plier, but the circlip only laughed at my effort. I did not want to remove the circlip with screwdrivers etc., which could ruin the machined slot in the torque tube. I purchased a heavy duty Knipex circlip plier (4811-J4, 320 mm), which made the removal easy (Wear eye protection, the circlip stores significant energy when compressed). Inside, it was hard to tell that this torque tube had been in service for 20 years and 178.000 km (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 driveshaft 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 to break the factory thread lock. I first tried without heating