MX5 NC Gearbox fitting guide

Prepping the gearbox

  1. Notch the gearbox to clear the starter. Offer the adaptor plate to the gearbox and loosely hold in place with a couple of the fixing bolts. The dowels on the adaptor plate will line everything up.
  2. Offer the starter motor to the plate and note where the nose of the starter clashes with the box.
  3. Grind out the box until the starter motor bolts up flush onto the adaptor plate.
  4. You may need to trim some of the additional webbing from the box to fit the tunnel of your car depending what car you are putting the box in to allow more space.

Cutting the hole for the cable clutch fork

  1. Mark out the cut for the hole in the side of the gearbox as per the dimensions below in the picture.
  2. Remove the existing release bearing by pulling it away from the fork. This is to ensure no swarf gets in the bearing.
  3. Cut the corners out using a hole saw. I use a 35mm saw but this can be slightly smaller or you can just cut it all square with a grinder.
  4. Cut out the rest of the hole with a grinder and then remove all burrs and clean out the bellhousing to remove any swarf.

Fitting the cable clutch pivot

  1. Remove the existing release bearing by pulling it away from the fork.
  2. Pull the fork out of the box
  3. Unscrew the original pivot point from the box.
  4. Remove the slave cylinder on the side of the box by undoing the 2 bolts..
  5. Remove the 12mm headed bolts from the 1 o’clock and 3 o’clock positions on the cover.
  6. Offer up and bolt on the new pivot point using the holes where the bolts just came from.
  8. Pass the new clutch fork through the hole made in the side of the box and then put the slotted end onto the pivot.
  9. Refit the original release bearing to the new cable clutch fork and then twisting to hold in position.

Fitting the hydraulic concentric release kit

  1. Remove the existing release bearing by pulling it away from the fork.
  2. Pull the fork out of the box
  3. Unscrew the original pivot point from the input shaft cover.
  4. Remove the input shaft cover from the box
  5. Cut off the input shaft cover guide for the original release bearing taking it flush with the ribs on the cover. 
  6. Refit the input shaft cover ensuring to clean everything and use a flange sealant like loctite 510 to reseal. 
  7. Remove the slave cylinder on the side of the box. 
  9. Bolt on the concentric release bracket using the 4 M8 cap head bolts provided.
  10. Pre fill the slave cylinder by submerging the pipe that would be connected to the master cylinder in brake fluid.
  11. Slowly squeeze the slave cylinder together and slowly release. repeat this slowly until no bubbles come from the end of the pipe.
  12. Bolt on the concentric release cylinder using the 3 M6 cap head screws.
  13. Make sure that the concentric release cylinder is sitting flush against the bracket and that there is clearance in the back of it between the input shaft cover/sleeve. 

Fitting the adaptor plate to the engine

  1. Remove all existing locating dowels on your engine.
  2. Offer the adaptor plate up to the engine and fit the top two countersunk bolts loosely
  3. Nip up one of the countersunk bolts to centralise in the hole.
  4. Fully tighten the second countersunk bolt and then go back and fully tighten the first one
  5. Fit the M10 x bolts with flat washers from the engine side into the adaptor plate and fully tighten.

Bolting the engine to the box

  1. Lift the box up to the adaptor plate and slide it over the locating dowels.
  2. Fit the M10 bolts that hold the box to the engine as shown below.