MX-5 / RX-8 Manual Transmission 6-Speed Change Control Bush Replacement

MX-5 / RX-8 / Fiat 124 Spider 6-speed change control bush replacement

This guide shows how to replace the change control bushes used in the Mazda MX-5 NC, Mazda RX-8 and Fiat 124 Spider 6-speed manual transmission. These bushes wear over time, introducing play and a vague shift feel. In more severe cases they can fail completely, preventing you from selecting gears.

Replacement is a straightforward job with basic hand tools. The guide below covers the three change-control bushes together with the optional reverse-gear bush.

Tools needed

10 mm socket or spanner
12 mm socket or spanner
6 mm drift or punch
3 mm drift or punch
Small flat-bladed screwdriver or trim tool
90-degree circlip pliers
Small pick tool
Light grease or oil
Rags and degreaser
Suitable silicone sealant for reassembly

Tip: Take a few photos as you dismantle the assembly. They are useful references for the oil chute, fastener positions and selector orientation during reassembly.

Note: A magnetic tray is useful.

Safety: Make sure the gearbox is securely supported it and take care not to allow dirt, loose hardware or tools to enter the gearbox while the change-control assembly is removed.

Remove the change-control assembly

Remove the 12 mm bolts securing the change-control assembly to the gearbox housing. Gently pry the assembly free, then turn it upside down onto a suitable clean work surface.

Warning: Do not allow hardware or debris to fall into the gearbox while the assembly is removed. Cover the opening with a clean rag while you work.

Removing the MX-5 RX-8 6-speed change-control assembly from the gearbox

Separate the change-control mechanism from the top plate

Remove the 10 mm bolts securing the change-control mechanism to the top plate. Make a note of the position and orientation of the oil chute, then place the top plate to one side.

Tip: Take a quick photo of the oil chute before removing the last fastener so its original position is easy to confirm.

Removing the 10 mm fasteners from the 6-speed change-control mechanism

Drive out the first selector pin

Use a 6 mm drift to drive the end of the selector pin flush with the surrounding surface. Once it is flush, continue driving the pin through using a 3 mm drift.

Driving out the selector pin to access the first change-control bush

Fit the first change-control bush

Remove the worn bush and fit the replacement bush onto the pin. A light smear of grease or a drop of oil will help the new bush slide into position.

Installing the first replacement change-control bush — A light smear of grease or oil helps the bush slide onto the pin.

Access the second change-control bush

Drift the pin through the selector fork and withdraw the rod to gain access to the second bush. Keep the components in order as they are removed so their orientation is clear during reassembly.

Fit the second bush and reinstall the pin

Fit the second replacement bush, using a drop of oil if required to ease installation. Reassemble the selector fork and drift the pin back through into its original position.

Installing the second change-control bush and reinstalling the selector pin

Reassemble the fork carrier

Once the bush and pin are correctly installed, refit the fork carrier to the top plate using the previously removed 10 mm bolts. This completes replacement of the first two bushes.

Reassembling the fork carrier after replacement of the first two change-control bushes

Access the third and fourth-gear selector bush

Remove the 10 mm bolt from the adjuster plate. There is no need to alter the adjuster itself for a bush replacement unless adjustment is specifically required.

Note: If the gearbox is selecting correctly before the repair, avoid moving the adjuster unnecessarily.

Removing the adjuster plate bolt to access the third and fourth gear selector bush

Replace the third and fourth-gear selector bush

Remove the circlip with the pick tool, replace the bush and then reinstall the circlip. The selector can then be reinstalled in the gearbox using the previously removed adjustment pin. Bolt the pin plate back into position and reinstall the circlip.

Warning: The circlip can spring away as it is removed. Work over a clear bench or tray and keep a finger over it while releasing it.

Removing the circlip to replace the third and fourth gear selector bush

Fit the optional reverse-gear bush

If you have purchased the Performance Delta reverse-gear bush, carefully pry the original nylon bush from the lever and press the replacement bush into position.

Tip: The replacement is intentionally a tight fit. Press the lever down against a clean piece of wood to help seat the bush fully onto the lever pin without damaging the component.

Installing the Performance Delta reverse gear bush on the 6-speed selector lever

Refit and reseal the change-control assembly

Clean the old silicone from the gearbox and top-plate mating surfaces so that both surfaces are flat and free from loose sealant. Apply fresh silicone sealant, refit the complete top-plate assembly and secure it using the original 12 mm bolts.

Final check: Before refitting the gearbox in the car, confirm that the selector moves cleanly through the gear positions and that all removed fasteners and circlips have been reinstalled.

Complete the gearbox upgrade

The change-control bush replacement is now complete. If you are refreshing or upgrading the complete MT6 change-control system, the Performance Delta gearbox upgrade set combines the complementary transmission upgrades in one package.

View the complete gearbox upgrade set