Transmission and Drivetrain

Diagrams

FAQ's

• Question

  What is the difference in the Borg & Beck, Diaphragm and Long-Style pressure plates?

  Answer

  The Diaphragm style is a multi-finger plate that takes less pedal pressure to release. The Borg & Beck and Long-Style are 3 finger plates that provide a higher clamping force.
• Question

  Why do I need to use a SFI-certified steel flywheel instead of a cast iron flywheel?

  Answer

  High performance applications must meet elevated performance requirements.
• Question

  What is the difference between Neutral (internal) Balance and Detroit (external) Balance Flywheels?

  Answer

  Neutral (internal) Balance engines and flywheels are each balanced as an individual unit. In other words, the engine and flywheel are in balance with or without the flywheel mounted to the crankshaft. A Factory Balanced (external), or Detroit Balanced engine uses the flywheel to balance the engine assembly. With the flywheel off of the engine, both the engine and flywheel are out of balance.
• Question

  What Hays flywheel do you recommend for my engine and what size Hays clutch can I use with it?

  Answer

  Hays offers stock size and weight as well as custom applications built to order.
• Question

  Why can't I get my clutch to release and shift properly after it is completely installed?

  Answer

  This is typically means the clutch needs adjustment. Adjustment procedures vary by vehicle and can be found in most service manuals.
• Question

  What starter do I use with Hays flywheels?

  Answer

  Most starters use stock or stock style unless otherwise specified.
• Question

  Which clutch kit to you recommend for my street/strip muscle car?

  Answer

  Street/strip clutches are available for most applications and can be found in our Hays catalog.
• Question

  How much static pressure clamp force do your Hays clutch pressure plates give out?

  Answer

  Street applications are rated up to 2,400 lbs and street/strip applications are rated up to 2,750 lbs.
• Question

  Should I use an aluminum or steel flywheel?

  Answer

  Aluminum flywheels with their lighter weight, are typically used in oval track and road race applications and are also popular in high-horsepower, light weight drag cars. These vehicles rely on engine horsepower to drive the wheels. Steel flywheels are used in applications that require additional engine torque for performance. A heavier flywheel can help acceleration from a standing start and keep the engine's RPM and power up through shifting. These are characteristics needed in street, most drag race and other high-torque applications such as tractor pulling.
• Question

  Should my new Hays Clutch be balanced before installation?

  Answer

  No, all Hays pressure plates and flywheels are dynamically balanced to extremely close tolerances. However, if you are having an engine assembly re-balanced, it would be a good idea to include the clutch components to insure tolerances be as tight as possible.
• Question

  What is static pressure?

  Answer

  Static pressure, also referred to as base pressure, is the amount of spring pressure (in pounds per square inch) that is exerted by the pressure ring to the clutch disc when the clutch is engaged.
• Question

  What is centrifugal or roller assist?

  Answer

  Certain Hays pressure plates feature centrifugal assist for increasing pressure plate load to prevent slipping and high RPM plate/disc separation. The Borg & Beck design utilizes rollers inside the cover that are forced to the outside under centrifugal force to increase plate load as RPM increase. Certain Long-Style pressure plates use levers that have extra weights on the levers to provide centrifugal assist.
• Question

  Can you install a clutch disc backward?

  Answer

  We receive returned discs for warranty that are installed inside-out and bent when a customer tries to put the disc in backward. With the flywheel installed on the engine, lay the clutch disc on the flywheel and rotate it some. It must sit flat against the flywheel and not be contacting the flywheel bolts as you rotate it. If the disc does not sit flat, make sure you have it in correctly.
• Question

  Can I use power tools to tighten the pressure plate?

  Answer

  We do not recommend this. Tightening down the cover puts a load on the clutch cover flange since you are pulling it down against the pressure of the diaphragm or coil springs. Using power tools can cause this flange to bend which will leave the fingers uneven once the clutch is fully tightened down. This can cause extreme clutch chatter.
• Question

  Which clutch kit to you recommend for my street/strip muscle car?

  Answer

  We offer our Hays Classic, Street 450, or Street 650 for most street/muscle car applications. Please see in our Hays website.
• Question

  Do I need to make sure I have proper release bearing adjustment?

  Answer

  Yes, setting the proper release on your clutch is very important — not only initially, but periodically going forward. A mechanical linkage should be adjusted for minimum release; that is only enough release that the clutch will disengage cleanly for shifting. This will result in a pedal lower to the floor and leave maximum free play. As the clutch disc wears, the fingers of the clutch will get taller, and if you have the bearing adjusted too close, it could ultimately unload the clutch fingers and not let the plate put its full load on the disc. This will cause undue slippage and wear. This applies to mechanical or cable type clutch linkage.
• Question

  My flywheel looked pretty good so I just went ahead and installed the clutch. Do I have to resurface my flywheel before a new clutch install?

  Answer

  We have been asked this many times. No matter how good the surface may look, if you want the new clutch to seat properly, it needs a fresh friction surface to seat against.
• Question

  Can I just change out the clutch disc only?

  Answer

  Obviously the clutch disc is the part of your system that will physically wear the most. Changing only the disc is setting yourself up for problems. As the clutch, disc, and flywheel wear in, the surfaces build a taper that the clutch disc will conform to. If you install only a disc, it is going to make contact on the outer edges only and will never properly seat. Ultimately this will cause premature slippage and will most likely chatter on takeoff.
• Question

  How should I adjust my clutch?

  Answer

  First of all, be sure all mounting fasteners are torqued correctly, this is very important. The actual adjustment will vary depending on the type of pressure plate being used. With the clutch pedal completely depressed, a diaphragm should have .030-.040 air gap between the disc and flywheel, for a Borg & Beck the air gap should be .040-.050 and for a Long-Style pressure plate it should be .050-.060. On vehicles with mechanical linkage, with the pedal released, an air gap of .250” should exist between the throwout bearing face and pressure plate fingers. On cable and hydraulic applications, the throwout bearing face should rest lightly on the pressure plate fingers.
• Question

  Can I tighten my pressure plates bolts down all the way 1 at a time?

  Answer

  No we do not recommend this. A way to damage the flange of the clutch cover is to tighten the bolts down completely in one shot instead of in a star-shaped pattern. This can damage the flange and also cause the fingers to sit unevenly. Tighten the cover bolts ONLY with hand tools, and use a star-shaped or crisscross pattern, a few turns at a time, just like torquing your wheels in place.
• Question

  Where do I need to send my flywheel back to in order to get it "recertified" for SFI?

  Answer

  Please refer to the "support" section of our website to fill out a repair form for recertification.