I maintain two taxis (both are 2008 BFIII Falcon wagons) and have recently decided that I’d better start paying some attention to the diff oil. Having changed the diff oil on both taxis this week, I figured that I’d better do the same with the personal car.
Before doing this, I took the car for a 15 minute drive to get the diff oil warmed up. When diff oil is cold it is very thick (ie much thicker than engine oil) and would take longer to come out when it’s cold. Plus, I was doing an engine oil change after this as well.
I started by reversing the ute up onto some ramps. I’m used to removing wheels, so it was quite a luxury to not stuff around with trolley jacks and axle stands. My driveway is also on a slight angle, so putting the ute on the ramps also had the added bonus of making the car level (required for re-filling the diff to the correct level).
There are very few tools required for this job. Because I’m doing the same tasks on Falcons all the time, I’ve bought a few tools that are a bit specialised.
Luckily, I already had the 30mm socket - that one is usually for motorbike rear axle nuts.
I bought the Sealey AK631915 15mm Double Ring Spanner via eBay UK a few months ago (do a search for that part number). With Falcons, the engine drain bolt and brake caliper bolts are 15mm head, and this 300mm long spanner gives me heaps more leverage than normal spanners. One end is a 15mm ratchet spanner and the other end is a 15mm ring spanner.
I bought the Ampro T29771 ratchet ages ago but never really took to it. Suddenly, I’ve started using it all the time. It’s a lot more bulky than my usual Sidchrome ratchet, but the way that it extends out gives me extra leverage. I bought that one via Amazon US, but local Ampro stockists should be able to get one in if you want one.
I got the Motive Products Power Fill 1740 a few weeks ago -
Motive Products #1 Selling DIY Brake Bleeder. You pump pressure into it so that it pushes the oil through. I haven’t been changing transmission fluid or diff oil on the taxis here so I figured that it was time that I started to.
What’s under the car - it’s all very simple. With the BF Falcon wagons (ie live axle rear end), the ABS sensors and rotors are on the wheel ends of the axles, whereas on this Commodore ute they are at the diff end.
Naturally, I made sure that I could loosen the fill bolt (30mm) before touching the drain bolt (15mm). If you don’t have a 30mm socket then you could probably get away with using a crescent/adjustable spanner, but if you round it off then you’ll be paying a few dollars extra for a six=sided impact socket.
I removed the drain bolt and the old diff oil started coming out.
The fill bolt. It didn’t have any thread sealant on it (no big deal).
I went off to do some other things and left the oil draining for a while. I turned on the tap for the pressure bottle to help clear out a bit more of the old oil before putting the drain bolt back in.
A closeup of the old oil and new oil. There’s quite a difference in appearance.
Diff oil is very thick, and so it takes a long time to flow into the diff. I’ve used the leftover from what I put in the taxis -
Penrite Gear Oil 85W-140 This is a mineral oil, but I’ll be replacing it with full synthetic oil next time - the mineral stuff will basically act as a flush. If I use Penrite again then it will most likely be
Penrite Pro Gear 80W-140
I did an engine oil and filter change after this, so climbed out from under the car and got things ready for that while the diff oil was flowing in. I checked under the car every few minutes and got back under there once I saw the excess oil flowing out.
I put the fill bolt back in and made sure that both that one and the drain bolt were in reasonably tight. You can use a torque wrench for this if you want.
The old diff oil was very, very dirty. I’ve tipped the drain pan forward and then backward to see it against the yellow background of the drain pan. This is one reason why I prefer drain pans that are a lighter colour (or at least not black) - you get a better idea of the condition of the old oil.
The good news was that there weren’t any metal filings. The diffs in the BA and BF Falcons are crap, and wear out relatively early. Check out these photos from my taxi - the metal filings are from the internal gears wearing out.
