Filling and Changing the Gearbox Oil

Do you have a Leaking Gearbox?

If your Fairway doesn’t pull along like it used to, or it’s not getting the top speeds that you hear other owners boasting about, then there’s a good chance the auto gearbox has something to do with it!

In my case, the acceleration was very poor, the car was barely getting above 50mph on a flat road and it was taking a boot full of revs to get the thing moving over my gravel driveway.

If you notice a few drops of red/brown oil left on the ground when you leave a parking space then, like me, you’ve probably got a leaky gearbox. My gearbox leak is slow, but after two years of being off the road, enough fluid had leaked out that meant the gearbox wasn’t transferring much power to the wheels.

In this case, the gearbox oil needs topping up and if you have time you can easily change the old oil at the same time.

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Draining the Gearbox Oil

Since I have never changed the gearbox oil in my Fairway, I decided to give it a go. At the same time I made sure I restored the correct level of fluid so the gearbox worked as it should.

The process is fairly straightforward and requires little more than a 19mm spanner for the oil plug, something to catch the old oil in (around 4 litres) and some new gearbox fluid to fill the thing back up with – Dexron II or Dexron III is suitable.

Firstly, jack up the front of the taxi or drive it onto some ramps so you can get access to the gearbox. The oil plug is on the bottom of the sump (not to be mistaken with the engine oil plug which is further forward).

Put a tray or bucket beneath the sump then remove the plug with a 19mm spanner or wrench. Mine was done up very tightly and required the use of a breaker bar to get it loose. About half of the old oil will drain out of the sump, which is around 3 or 4 litres (the total capacity of the gearbox is 7 litres according to the manual). The remainder stays in the torque converter and doesn’t drain. If you want to flush the whole system then repeat this entire process again.

In my case the oil was a chocolate like colour and had a burnt smell, suggesting it hadn’t been changed for a while. If the oil was black or much darker there would be cause for concern and may suggest a more significant problem with the gearbox. The new oil which goes in is a cherry colour and smells fresh.

Having drained the old oil, now would be a great time to remove the gearbox sump and change the filter and gasket. I don’t have either of these parts to hand so this is a job for the future – I’m mainly interested in getting the car moving like it used to!

Filling the Gearbox Oil

Assuming your gearbox wasn’t overfilled before you drained it, fill the gearbox back up with the same amount of new oil. You’ll find the filling hole and dipstick hidden away between the blower and the rear of the engine block. It’s quite low down so you may have to stand on the bumper to get to it.

Reading the level of the gearbox oil requires a warm engine. Even though the dipstick has a ‘COLD’ range on it, this is inaccurate and you’ll find this significantly overreads compared to a warm reading.

Run the engine at idle for 2-3 minutes, then with the handbrake applied, alternate between 1st Gear and Reverse leaving ten seconds each time. This will prime the gearbox and give you an accurate reading within the ‘HOT’ range of the dipstick.

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If you’re doing a straightforward oil change, there should already be the correct level of fluid because you’ve refilled with the same amount.

If there still isn’t enough fluid, or you’re not sure if the dipstick has old or new oil on it, a great place to look is inside the lower of the convex bumps on the dipstick. This area doesn’t drag up any of the fluid which you’ve just poured down the filling tube so if it’s still dry then keep gradually filling up the oil. Remember to reprime the gearbox each time you recheck the level and repeat as necessary. Once the oil is clearly on the inside of the lower bump, you can add small amounts to bring the oil level within the two lines of the HOT range.

In my case, I needed an extra 1.5 litres of oil! With some relief, the gearbox was now working as it used to. I haven’t taken it for a drive on the road, but I could tell just by running up and down the driveway that it had much better acceleration than before.