Pedal to the metal and dump the clutch! I have done this with every vehicle with a manual transmission I owned and I have never, ever regretted it. Increased wear and tear will definitely happen and component failure is a high risk. Why do we push our machines to the breaking point? The adrenaline rush of the sound; feeling and understanding what is happening internally in our machines is nothing short of beautiful and amazing. Let’s go through the steps of removing and installing a clutch assembly.
- Before proceeding, disconnect battery power to prevent the engine from being cranked while the clutch is removed and reinstalled if your engine is still in the vehicle. Our engine was out, so it was uber simple.
The 350 Chevy engine has an outer bellhousing which protects the flywheel, clutch disc, throwout bearing, fork, and pressure plate. This must be removed first. From there, removal and installation is straightforward, so I included industry standard practices and processes to ensure this is applicable to any vehicle.
Removing Old Clutch assembly
If you decide to reuse your old pressure plate and just install a new clutch/pilot bearing, be sure to mark both pressure plate and flywheel. This is necessary so the balance of the flywheel clutch assembly will not be off and cause excessive NVH.
Remove the Pressure Plate
- Remove the throwout bearing out of the throwout fork.
- If more clearance is needed for removal of these components, disconnect the clutch linkage from the fork, which in turn will allow the fork to be tipped back or removed entirely.
- Loosen each pressure-plate-to-flywheel fastener one full time at a time to allow an even release of the pressure plate. This process prevents twisting or warping of the pressure plate. You can insert a clutch disc pilot shaft or dowel through the clutch disc hub and into the crankshaft pilot bearing to hold the disc in position until the pressure plate fasteners are removed. A spare or used transmission input shaft could be substituted as well.
- Remove the pressure plate and disc by pushing in and up while removing the last fastener. Do not touch the friction surfaces with greasy fingers.
Clean the friction surfaces with non-petroleum-based cleaner. Brake cleaner is perfect. Just try not to inhale too much!
Never wash the throwout bearing due to the bearing grease that is packed inside of the component. Instead, wipe off any dirt or excess grease on the outside. If the bearing has heat marks or other damage, replace the throwout bearing.
Sanding Clutch Friction Surfaces
Using a medium to fine emery cloth or aluminum oxide paper to sand the friction surfaces of the flywheel and pressure was sufficient for our parts. The clutch and pressure plate are still in good condition, and we decided to reuse them after removing the glaze from the friction surfaces.
Using the sanding paper, apply light pressure in a back and forth motion across the parts until the surfaces are covered with fine scratch lines. The sanding scratch marks should be going across the surface end to end. This process breaks up the glaze of the surface and removes any carbonized oil deposits.
If the glaze can not be removed with sanding, the components may be machined. This requires a shop to perform this task with special equipment.
Inspecting the Flywheel-to-Clutch Friction Surface
The surfaces must be clean, dry, lightly sanded and without heavy heat checking (cracking and heat spots). Also, make sure no major scoring or warpage is present.
Checking Flywheel Runout
With the flywheel still installed on the engine, set up a dial indicator and rotate the crank/flywheel assembly. Rotate the flywheel in one direction until it has completed two full rotations while checking the dial indicator measurements.
0.005-0.009″ of runout is acceptable. The flatness of flywheel mounting surface to the mounting surface to the crankshaft needs to be less than 0.002″.
The crankshaft flange must be clean and true. The same process as for the flywheel runout can be used on the crankshaft flange with a dial indicator.
- Install the flywheel and install cap screws with oil-resistant sealer.
- Lock washers can be used to ensure everything will stay torqued.
Some flywheels, mostly newer and imports, use a hardened plate intended to protect the flywheel against damage from the bolts or cap screw heads. If this clutch contact face is scored in anyway, it must be reground or replaced.
Flywheel Ring Gear Removal
If for any reason you need to remove the ring gear from the flywheel, you should send it into a professional shop for this process – or you can follow the steps below.
- Heat up the ring gear so it expands and drive it from the flywheel.
- If the ring gear is welded to the flywheel, grind off the welds and continue with the above procedure.
- If necessary, the ring gear can be drilled and chiseled to spread the gear from the flywheel. Do not hit the flywheel.
- If this is beyond your skill level, you can send the flywheel in for a professional to complete the ring gear removal and installation.
Flywheel Ring Gear Installation
- Shrink-fit ring gears should be heated up to no more than 450 degrees Fahrenheit. A controlled oven is ideal for this purpose and should be handled with caution. If a oven is not available, heating oil and submerging the ring gear into the oil bath will do the job as well. To avoid a fire, cover the tank while heating.
- Chill the flywheel to shrink the flywheel. This helps slightly.
- Line up the ring gear to the flywheel and drive it into place.
- If your ring gear was welded, add another arc-weld to the ring gear and flywheel. Use the smallest amount of weld for this too.
Checking Pressure Plate Assembly
- Check and inspect the pressure plate for excessive burning, heat checking, warpage and scoring. This is very important if you are reusing a pressure plate.
- Check the coils or diaphragm springs for any signs of cracking, loss of temper (overheating) and looseness.
- Check for wear and tear at the ends of the release levers (fingers) where they make contact with the throwout bearing.
- If any signs of wear or damage are present, replace the unit with a new pressure plate assembly.
Replacing the Clutch Pilot Bushing or Bearing
The pilot bushing, or bearing, is installed in the rear of the crankshaft and supports and aligns the transmission input shaft. It is always a good idea to replace this component, since everything is removed for easy access.
- Use an expandable finger or threaded puller to remove the pilot bushing/bearing.
- With the new pilot bearing/bushing in hand, lightly apply high-temperature grease on the outside.
- Using a pilot driver tool, ensure the chamfered inner hole end is facing outward, away from the engine, and drive the bushing into place.
- When installing a pilot bearing, make sure the open side of the bearing is facing inward (seal end facing transmission) and high-temperature grease is applied inside of the bearing.
Aligning the Clutch Housing as Necessary
The engine and transmission mating surfaces must be clean, flat and properly aligned to avoid premature failure of components. Short throwout bearing life, clutch chatter, input shaft bearing failure and jumping out of gear might be caused by housing misalignment.
Installing the Clutch Disc and Pressure Plate Assembly
The installation process is very straightforward; however, careless handling of parts, improper tightening and disc damage during transmission installation can lead to ruined components or shortened lifespan of the components. (e.g. clutch disc, throwout bearing, etc).
- Repair any fluid leaks that could potentially contaminate the clutch disc and friction surfaces.
- Use a new clutch disc when possible. If you have to reuse a clutch disc, ensure the splines do not have excessive wear. Generally.003” is the maximum of hub spline wear allowable. If the disc is faulty or damaged in anyway, it must be replaced.
- Install the clutch disc with the correct side facing the flywheel. Check for markings on your clutch disc before install.
- Use a clutch disc pilot shaft to align the clutch disc and pressure plate while tightening the pressure plate fastener.
- Use lock washers with pressure plate bolts. Tighten the fasteners evenly so the pressure plate does not become cocked or misaligned.
- The throwout bearing should be replaced as good practice, but if the old one must be reused, ensure it spins freely and does not have any signs of damage.
- Lubricate and install the clutch throwout fork.
- DO NOT DEPRESS CLUTCH PEDAL UNTIL INSTALLATION IS COMPLETE.
This is a fairly easy task to complete. If you want to skip the technical side of things, just make sure you have a new pilot bushing/bearing, flywheel, clutch disc, pressure plate, throwout bearing, oil-resistant sealer for flywheel bolts and necessary tools. And always be sure to align the clutch disc and pressure plate before torquing the pressure plate to the flywheel. The use of a pilot shaft or dowel is always needed.
- 35 ft lbs – pressure plate to flywheel
- 60 ft lbs – Flywheel to crankshaft