Today we are servicing the automatic tranmission on this E46 325ti Compact.
The car has covered only 46000 miles, and drives faultlessly. BMW claim that the ATF is ‘lifetime’ oil and never needs replacing, however we all know that in the real world even the best specification oils degrade, and what exactly does Lifetime mean? Whilst the number of Automatic transmission failures is low, we believe that the lifetime can be extended with an automatic transmission service every 30k miles at most. Some auto specialists suggest as low as every 12k, but this is unrealistic as the correct oil is expensive.
7 Litres of the correct ATF – this box takes Esso LT71141 Synthetic fluid
New bolts or loctite if re-using the old bolts
A new sump gasket
To do this job the sump needs to be removed.
Your sump will have a sticker attached, this details the BMW part number for the oil that is for your transmission. If the sticker is missing then you’ll need to look for the plaque that is on the transmission itself, and determine the model number. You can then trace what oil is specified for your particular transmission.
And here is the gearbox plaque in this case a ZF-5HP19.
Now its time to drain the oil from the transmission. This needs to be done from cold to ensure that a large amount of the oil has returned to the sump. Below 30c temp is advised, which can be checked on a BMW diagnostic machine. If you don’t have access to this, then just ensure that the car has been parked up outside for 3-4 hours, the oil will be cool enough. Some automatic specialists don’t let it cool and just drain it hot, but I’ve seen a difference of up to 2 litres extra when draining cold. Before you drain, it’s a good idea to check that the FILLING plug loosens OK, if it doesn’t for any reason then you need to stop the ATF change until you have a new fill plug available. The drain plug on this transmission is a 6mm hex. Drain the oil into a measuring jug so you can see how much oil comes out. You will need to know this for later when refilling the transmission with new oil.
Now this transmission has covered just 46k miles. The oil should be clear, but as you can see above it’s very dark and dirty. A sure sign that lifetime oil is not quite good enough. Once the oil has drained, refit the drain plug and it’s time to remove the sump itself. Undo the 22 T27 torx bolts that secure the sump to the transmission.
Once they are undone the sump will attempt to fall down so be quick to grab it. I’ve placed it on a transmission jack here to catch any remaining fluid still draining. Be aware that the sump will still have 250ml of fluid sitting in it, so be sure to tip that into your measuring jug so you get a final amount of oil drained. See the sump removed below, it’s a good idea to wait a few more minutes for any remaining oil to drain into the sump before emptying into your jug.
Now that the sump is removed you can see the filter that is attached. How BMW and other manufacturers can recommend that this never needs replacing amazes me.
So let’s get the filter removed. It’s secured by 2 x T30 Torx bolts as you see below.
Once you’ve undone the 2 torx bolts the filter will simply pull downwards. A little extra oil may spill out, but don’t worry about this as it’s not a lot of oil so doesn’t need to be saved. Ensure that the seal has also come out with the filter that slides up in to the transmission as seen below, you will not need to keep this seal as the new filter comes with a new seal attached.
On this car we are going to fit a new sump pan. This is not required but the owner has requested a new sump because it looks nice. 🙂 Here is the new sump and the new filter. You can see the new bolts too. They have a spring washer attached that compresses on fitting, this is why techincally they should be used only once. Due to the expense though at £45 or so people may prefer to reuse the old bolts which is ok if using a little Loctite when fitting.
A new sump comes with a nice new sticker 🙂
Here is the new sump alongside the old sump. Note the small magnets fitted that keep hold of any metal particles from the gearbox, including any metal particles from the clutch plates and bands that are inside the automatic transmission. You can also see the sludge that has formed from OLD oil that has been through many many heat cycles. If reusing the old sump be sure to clean ALL the sludge and residue in the sump and on the magnets.
Here’s some of that sludgy mess. Changing the oil every 30k will minimise the sludge formulation and ensure the whole transmission remains clean and well lubricated.
Now remove the old gasket and clean the surface of the transmission with a clean cloth and some brake cleaner, this will remove any ATF that is on the surface. You must then fit the new sump and gasket (pictured below).
Fit the new sump with the bolts. Tighten the bolts in sequential order and ensure that your drain plug is tight. The filling procedure is detailed below, and should be done with a BMW diagnostic machine monitoring the ATF temperature.
Measure the total amount of oil that you drained into your jug earlier. We drained 5.5L in this case, but this will vary. Fill the tranmission through the filler with the engine OFF with the same amount (5.5L in this case) of the new oil – Esso LT71141 is this transmission. Now refit the filler plug and start the engine in park. Hold foot firmly on the brake pedal and shift through the gears R, N, D then manual gears 1,2,3. Hold each gear for 3 seconds. Reading the diag machine ensure oil temperature gets up to 40-50c – put the vehicle in P and remove filler plug. If oil exits the fill hole then the level is correct, if not then add more oil until it exits.
Turn engine off. Job done. Check for leaks and clean any ATF residue from sump/exhaust etc.
Any questions or comments feel free to post and we’ll answer as soon as we can.