Getting Access

1. Apply the handbrake firmly & place the car in 3rd or Park.

2. Remove the airbox (12mm socket & long extension bar) and intake tube between it and the throttle body (philips screwdriver). Beneath the airbox sits the transmission and fill-plug can be located on the front part way up.

3. Jack the car up via a Hydraulic Jack under the front jacking point nub only and place safely on jack-stands. See the Hydraulic Jack & Safety Stand Positioning section.

Draining Gearbox Oil

4. Ensure the fill-plug can be removed before removing the drain plug. Place an oil-pan under the drain plug of 4Q capacity and drain the gearbox oil out of the transmission. A new washer must be fitted to the oil drain plug and tightened to 40-58Nm, 29-43lb/ft.

Refilling Gearbox Oil

5. Lower the car off the jackstands until it is level, otherwise the gearbox will be under or overfilled - overfilling can blow out seals.

6. With the car level, using a "turkey baster" or funnel-&-tube, fill the gearbox with 2.7 litres (2.9 US Quarts) of oil until the oil level reaches the bottom of the fill-plug hole. Ensure exactly 2.7 litres of oil have been added.

7. Replace the fill plug with a new washer & torque to 40-58Nm, 29-43lb/ft.

8. It may be worth measuring the volume of the drained oil to see if the gearbox has suffered any leaks regarding the numerous seals. Low oil conditions in an MTX can result in inability to stay in 5th gear (Mazda and Honda) and eventually gear-teeth overheating & hardening breakdown. An MTX gearbox has transmission losses of 15%, largely in the form of heat which for 120kW can mean up to 18kW of thermal input into the oil. A full synthetic gearoil handles higher temperatures than non-synthetic.

Tightening Torques:

Drain Plug Tightening Torque: 40-58Nm, 29-43lb/ft.
Oil Fill Plug Tightening Torque: 40-58Nm, 29-43lb/ft.
Oil type & Quantity, Synthetic Redline MT90, GL-4 75w90, 3 quarts

Other oils

1. There are several suppliers of gearbox oil, which would meet GL-4 75w90. Examples are Amsoil, Motul, Comma and so on. In practice Redline MT90 GL-4 75w90 is found to work the best amongst Miata & 626/MX6/Probe owners.

If a GL-5 oil is used it must be compatible with brass/bronze synchros - most are not, they are corrosive and so the oil manufacturer should be telephoned first. Use of the wrong oil will halve the life of synchros & bearings. Mobil1 74w90 GL5 is not suitable for our gearboxes - Mobil UK confirm its application is rear-end differentials (eg, Miata/RX7/BMW).

For local suppliers of Redline Oil in USA, UK, Europe or Canada contact RedlineOil directly.

2. The benefits of a synthetic gearbox oil are considerable; far less wear, better cold shifting & less cold-wear, better tolerance of heat (gearboxes run hotter than many realise with differential & gearbox combined into one).

Additionally, use of synthetic oils throughout the vehicle is one way to reduce friction particularly during warm up periods, and so reduce fuel burnt unnecessarily and so aiding the environment. Across the world population of vehicles the benefits over total ownership are considerable in both financial & environmental terms.

Last Upload: 31st January, 2002. V1.50a
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