This is a guide for changing your gearbox oil, this relates directly to a 120d, but I'm sure it would be a similar procedure for any BMW. I did mine on a ramp, which is preferable to stands.
Before you start, you'll need 2 litres of gearbox oil; a pair of rubber gloves (unless you prefer the spare bed), an 8mm Socket/Ring Spanner; an 8mm Allen Key; something to catch the old oil in; and tool/method for refilling the gearbox. I used one of these:
It's a 500ml 'Silverline' Oil Gun, basically a big syringe, which makes things very easy. About £8.
For best practice, you should also renew your gearbox plug seals, which involves buying 2 new plugs from BMW. About £4 each. Take the last 8 digits of your chassis number into your local friendly parts dept to make sure you get the correct items.
The oil BMW recommend is made by Castrol, but I wanted to improve a slightly notchy gearchange I was suffering, so went for 2 litres of Redline MTL, as recommended by Redline (and Blackbmw116 on here) for notchy E Series BMW manuals.
EDIT: For My F Series M135i (which requires LT-5), I went with 2 x Febi Bilstein 39070 , as recommended by Opie Oils. Highly recommended.
Start by removing the eight 8mm screws with secure the transmission portion of the undertray. The under tray will now be loose, but will require a 45 degree twist toward the OSR to drop from the car.
Under-tray unscrewed, just before 'twist' removal:
You'll now have a good view of the gearbox. Have a quick look at your new plugs, this will help you identify the Fill and Drain Plugs on your casing (and also how long those threads are for the next stage). Bear cleanliness in mind too, you don't want to knock any crud inside at any stage, or you could do more harm than good.
Fill & Drain Plugs:
Slacken the top Fill Plug first. Don't remove it yet though. If you remove the Drain Plug first, and have difficulty in removing the Fill Plug, you'll be left stranded with a car with no oil in her, and a headache! (thanks Anthony) Pop your gloves on (old gear oil is nasty stinky stuff), and with oil catch-can/tray in hand, remove the Drain Plug. As you've left the Fill Plug loose but still in it's hole, the oil won't come rushing out. My old oil was like black water, no wonder my change felt crunchy, 'sealed for life' my arse. Sealed to die, more like it. Once you've lost about a litre and a half, take the Fill Plug out, and go and have a cuppa, to let it drain for a while.
Nice brew? Good. Now it's refill time. Gloves back on, and fit a new Drain Plug in the bottom of your box. The seal does the work, not the Plug, so there's no need to go swinging off the Allen key with a great big long bar! Fill the gearbox with roughly 1.6 litres of nice new oil. I simply sucked it out of the bottle, and blew it into the fill hole. When it's full, it will just start trickling out the fill hole.
Refilling with Redline MTL via Oil Gun Syringe:
Now you just need to refit the Fill Plug, and replace the undertray. Again, no need to go crazy when torquing up the 8mm undertray screws.
If you went with the Redline MTL, go and enjoy your new smoother gearchange. The Castrol camp only get to feel smug about increasing the longevity of the box I'm afraid.
Before you start, you'll need 2 litres of gearbox oil; a pair of rubber gloves (unless you prefer the spare bed), an 8mm Socket/Ring Spanner; an 8mm Allen Key; something to catch the old oil in; and tool/method for refilling the gearbox. I used one of these:
It's a 500ml 'Silverline' Oil Gun, basically a big syringe, which makes things very easy. About £8.
For best practice, you should also renew your gearbox plug seals, which involves buying 2 new plugs from BMW. About £4 each. Take the last 8 digits of your chassis number into your local friendly parts dept to make sure you get the correct items.
The oil BMW recommend is made by Castrol, but I wanted to improve a slightly notchy gearchange I was suffering, so went for 2 litres of Redline MTL, as recommended by Redline (and Blackbmw116 on here) for notchy E Series BMW manuals.
EDIT: For My F Series M135i (which requires LT-5), I went with 2 x Febi Bilstein 39070 , as recommended by Opie Oils. Highly recommended.
Start by removing the eight 8mm screws with secure the transmission portion of the undertray. The under tray will now be loose, but will require a 45 degree twist toward the OSR to drop from the car.
Under-tray unscrewed, just before 'twist' removal:
You'll now have a good view of the gearbox. Have a quick look at your new plugs, this will help you identify the Fill and Drain Plugs on your casing (and also how long those threads are for the next stage). Bear cleanliness in mind too, you don't want to knock any crud inside at any stage, or you could do more harm than good.
Fill & Drain Plugs:
Slacken the top Fill Plug first. Don't remove it yet though. If you remove the Drain Plug first, and have difficulty in removing the Fill Plug, you'll be left stranded with a car with no oil in her, and a headache! (thanks Anthony) Pop your gloves on (old gear oil is nasty stinky stuff), and with oil catch-can/tray in hand, remove the Drain Plug. As you've left the Fill Plug loose but still in it's hole, the oil won't come rushing out. My old oil was like black water, no wonder my change felt crunchy, 'sealed for life' my arse. Sealed to die, more like it. Once you've lost about a litre and a half, take the Fill Plug out, and go and have a cuppa, to let it drain for a while.
Nice brew? Good. Now it's refill time. Gloves back on, and fit a new Drain Plug in the bottom of your box. The seal does the work, not the Plug, so there's no need to go swinging off the Allen key with a great big long bar! Fill the gearbox with roughly 1.6 litres of nice new oil. I simply sucked it out of the bottle, and blew it into the fill hole. When it's full, it will just start trickling out the fill hole.
Refilling with Redline MTL via Oil Gun Syringe:
Now you just need to refit the Fill Plug, and replace the undertray. Again, no need to go crazy when torquing up the 8mm undertray screws.
If you went with the Redline MTL, go and enjoy your new smoother gearchange. The Castrol camp only get to feel smug about increasing the longevity of the box I'm afraid.