This is the second part of my post on Changing the Rear Differential / Transaxle Fluid and Filter on a DB9. You should really check out my previous post and video on draining the rear differential fluid first as this is a continuation of that process (you can find it here).
We left off with the car in the air, rear under tray removed, drain & fill plugs removed, oil drained and filter removed. Time to get on with putting it back together!
Tools needed (in addition to those listed in the first part of the series) include:
- Torque wrench
- Gear Oil Pump (that you can attach directly to the 1 liter bottles available for about $11 online)
You’ll also need your replacement parts and fluids, namely:
- 2 liters of Aston Martin approved Shell Spirax S6 AXME 75W-90 lubricant
- Aston Martin P/N 704349 available online for about $17 per liter (in a 12 pack case). If you want a single bottle you might need to try your dealer.
- Here is the datasheet on everything you’d ever want to know about this lubricant
- [Updated Dec 2019] Apparently Shell has discontinued Spirax S6 AXME 75W-90 and directly replaced it with Spirax S6 AXRME 75W-90 (there is an extra R now in the model). A sharp eyed reader left a detailed comment below documenting the change and response from Shell when he inquired [Thanks for sharing that info]. If you are a skeptic and want to compare the Technical Data Specifications of the Old one (click here to read it) to the New one (click here to read it).
- Neither the old or new Shell part is readily available in the USA apparently. In the USA I had to substitute to Castrol Syntrax 06674 Limited Slip Gear Oil 75W-90. It has matching specifications and is made for a limited slip diff. You can read up on the Technical Data Specifications here. A 6-pack of 1 litre bottles costs about $72USD on Amazon.com with free Prime shipping (about $12 per bottle). A six pack of this will be enough for three fluid changes, so you are covered for 6 years.
- 2 new copper gaskets for the drain and fill plugs
- Aston Martin P/N 4G43-27-10245 and go for about $2 each online
- new filter (optional if you opted to clean the old one thoroughly)
- Aston Martin P/N 4G43-27-10490 and goes for about $100 online
- new O-ring for the filter (optional if your old one is in good condition, but how can you tell until its leaking – so I recommend splurging a couple of bucks on a new one)
- Aston Martin P/N 4G43-27-10491 for about $2 online
Cleaning of the old parts
Do your best to thoroughly cleanup the old parts you intend to reuse, including:
Drain Plug – Note that it has a magnet built into it to capture fine metal particles. You should check this after it you removed it. It’s normal to find a very small amount of metallic sludge on the magnet – this is regular wear and tear to the gears. If you find larger particle sizes or a LOT of metal, you might want to take some photos and get in touch with your dealer as you have a bigger problem brewing. After you’ve had a look at it, just give it a simple cleanup with a rag and some cleaning solvent.
Fill Plug – just give it a simple cleanup with a rag and some cleaning solvent.
Filter – If you plan to replace it, you can just toss the old one. If you want to reuse it, you’ll need to clean it out using solvent. Cleaning the outside of the screen is only part of the process, be sure to clean the inside and get all the accumulated debris out of the inside by rinsing through the passages.
O-ring for filter – If you plan to replace it just toss it. If you want to reuse it you can carefully pryse the old one off the filter while its being cleaned. Check it for any signs of flattening or cracking. If you spot ANY potential imperfection, just opt to replace it. If it’s in good condition just wipe it down (no solvents – they may make it swell).
Start by fitting a new O-ring to the filter. Apply a little bit of the new lubricant to it to make this easier. Install the filter into the differential housing and replace the two 8mm bolts, torqueing them to 5 Nm (snug).
Install the cleaned drain plug along with a new copper gasket. Use the 14mm hex socket and torque to 49 Nm (36 ft-lbs).
Now it’s time to add the lubricant. Position your drain pan below the fill port. Connect your Gear Oil Pump to the first bottle of gear oil and run the tube up into the fill hole. Manually pump in the first liter, and then change to the second bottle. Fill more slowly this time watching for the first signs of oil dribbling back out the fill hole. You need to add approximately 1.7 liters of fluid. Once the oil is dribbling out, remove your fill tube and allow it to continue to dribbling out until it slows to just barely a drip (this way you can be sure it’s not overfilled).
After it’s slowed to a drip, it’s now time to install the Fill Plug along with a new Copper Gasket. Use your 22mm socket and torque the plug to 49Nm (36 ft-lbs). Be especially careful not to damage the fins on the oil cooler that is right beside this area.
Meticulously wipe down the outside of the differential housing to remove any traces of old fluid or new drippings. You want to do this now so you can spot a new leak of any kind (besides, you want your Aston looking sharp!).
Drain all the used fluids from your drain pan into an old container like a used milk jug and then take it to a proper disposal center like a local auto shop for recycling (thanks Pep-Boys!). Take all your oily rags, gloves, paper towels and cardboard and dispose of those in the trash. They stink (like the gear oil) and you don’t want to keep oily rags in your garage for the fire hazard.
Here is a short video on the process I followed:
At this point all you have left to do is replace the rear under tray and lower the car back to the ground if that was all you were doing.