Or should I say how to help prevent Rumblings from a Mazda Box. So what could cause your box to rumble? Well, the simple answer is lack of oil i.e. To the correct level. This will cause reduced oil feed to the rear prop-shaft slip yoke support bush/bearing that is located behind the seal at the output (exit) of the gearbox tail housing.
(Photo 1) Shows the oil feed gallery to the prop-shaft slip yoke support bush/bearing
(Photo 2) Shows damage to the slip yoke support bush/bearing located behind the seal in the exit to the gearbox tail housing.
(Photo 3) As you can see here the lack of oil to this point has also damaged the prop-shaft slip yoke. Other problems that will cause damaged to the gearbox tail housing slip yoke bush/bearing and seal is an out of balance or bent prop-shaft.
(Photo 4) A bent prop-shaft can occur when the prop hits the gearbox tunnel normally due to axle tramp or bent/worn leaf springs. (Simple cure, fit new leaf springs and upgrade by fitting anti-tramp bars).
(Photo 5) A bent prop-shaft will accentuate the stress to the prop-shaft’s universal joints to the point they will fail. A bent prop-shaft will also damage the slip yoke support bush/bearing in the exit to the gearbox tail housing as the prop-shaft will not be spinning true.
When a new Mazda gear box is shipped, it comes with bottles of 70w-90w Mazda gearbox oil as standard. (The UK supplier is Vitesse Global Ltd, located close to Nuneaton)
(Photo 6) The volumes required are; 290ml to 330ml for the Shifter Housing. 2 Litres for the gearbox housing.
NOTE. Shifter housing is a separate unit and is not feed from the gearbox housing. it is filled as a separate entity and sealed from the gearbox. Now for anyone that has changed their Mazda gearbox oil the chances are you have had one or both of the following issues occur:
Point A: only changed the main gearbox housing oil and did not change the oil in the separate shifter housing.
Point B: Could only manage to fill the Mazda box with 1.65L as it runs out of the oil level plug.
For Point A. You need to re-visit your gearbox and fill with 290-330ml with 75w-90w oil
For Point B. The Mazda gearbox bell housing; when fitted to a Duratec engine, is canted over by 9 degrees, this leaves a short fall of 75w-90w oil as the level plug is now in a lower position.
The oil short fall is about 350ml. Not only is the oil gallery feed to the slip yoke support bush/bearing located behind the seal in the exit to the gearbox and is therefore in a higher position, there is also a lack of sufficient oil level. This combination causes oil starvation to the support bush/bearing and accelerated wear.
(Photo 7) Trusty Custard Cream Inclinometer gives a 9 degrees reading or 8.80 degrees to be more accurate on a levelled chassis.
Part 2 tips on how to fill your box adequately and change the separate shift housing oil.