Baby BMW Forum banner

How To Change Your Gearbox Oil

128K views 181 replies 62 participants last post by  p0otzz 
#1 ·
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:
Gearbox1.jpg


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:
Gearbox2.jpg


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:
Gearbox3.jpg


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.
 
See less See more
4
#129 ·
FirBim said:
Yes, it does. Did mine tonight, following Marco's excellent how-to. I realised (after refitting everything and lowering the car) that I had overfilled. Two 950ml bottles of Redline MTL is 1900ml, so I should've had about 300ml left in one bottle. There wasn't that much, maybe 100-150mls.

I jacked it back up, using the front jacking point on one side and the rear jacking point on the other side. This allowed me to lift the car more 'level' until there was just enough room to wriggle under. Dropped the undershield and removed the filler plug, and about 150-200mls drained out. Wiped clean, put everything back again. Mental note to remember elementary geometry in future....
I did mine on the weekend. The car was on ramps on the front and axle stands at the rear - it looked level but wasn't, being tilted down at the rear. This meant I could get more oil in the gearbox than required. If you overfill you can create more drag and maybe foaming issues, so I got the car level and the same happened as in the above quote. It was the diff that showed me it wasn't level - as I undid the diff plug the oil came out...

The existing diff oil wasn't too bad and still yellow. The gearbox oil was black and free flowing. Car has done 100k+ so maybe the diff oil has had a change at some point or it doesn't get too bad.
 
#130 ·
A big thanks to Marco_Polo for the gearbox and diff guides. I used these guides about 6 months ago to change my gearbox and diff oil. I'm not the most mechanically minded but I bought an oil gun as recommended and used redline for both, the guide was so simple to follow, so a big thank you.

It's good peace of mind, my car was on roughly 50k, the gearbox oil wasn't too bad, but the diff oil came out like black water! On that basis I'll change the diff oil annually.
 
#132 ·
I changed the gearbox oil on my manual M135i today. Car only has 15k miles on it so it definitely didn't need doing but I thought I'd do it as preventative maintenance. The fluid that drained out was black with specks of metal in so I'm glad they're not in there now. I refreshed with OEM MTF LT5 fluid. Fairly straight forward with the car on ramps on the driveway but it was tricky undoing the fill bolt with limited access wriggling around under the car and it was seized on too so I had to use a breaker bar.

For reference the steel fill/drain plugs require 45Nm tightening torque.

Shouldn't need to be done for another 30k now.
 
#133 ·
#136 ·
I'm going to attempt this soon to my 130i. Ordered 2L of gearbox oil.

DIY is perfect! I just have one question:
I need to fill 1'6L, if I try to fill more, oil won't come in and will be getting out thorugh the same filling hole? I'm afraid to overfill if there's some old oil inside the gearbox :rollseyes: .

Should I fill until the limit then and this will be 1'6L inside the gearbox?
 
#137 ·
It's a bit of a ***** to be honest as you have to make sure you suck it all out. Use a thin tube so you can get to the bottom. That's the biggest problem. because you read online how much the gearbox takes and then it seems not to take anywhere near that amount. It's obviously because you didn't get it all out.

But if the car is level. And you start pumping it in, when it starts coming out of the same hole, it means you have finished. Simple as that really. If the car is not level. You will either not put enough in or too much...a bit either way won't make any difference so don't worry too much about it.

Sent from my SM-G935F using Tapatalk
 
#138 ·
Just completed this on my 2009 123d (along with engine oil, fuel and air filters...) and it feels like a new car. Gearbox is amazing now. Great guide.

Did it with the front of the car jacked up. Drained the oil (soupy black with flecks in it...), fitted new plug (I used M18 x 1.5mm sealing plugs off eBay - ended up being a slightly shorter length, but doesn't matter) using the gooduntight torque setting, and put both bottles of Redline MTL in with the Silverline syringe. Used up both quarts of oil - never overflowed, but I pinky tested it and could feel it just inside the hole so figured it was fine. Re-sealed and car felt new again. Have done 30 miles of 'spirited' driving and it's been fantastic. Can't recommend enough.
 
#140 ·
The lower plug is certainly recommended/best practice, you'd be a very sorry boy if that one let you down.

£12 well spent (imo), vs hundreds in a recon box + labour. The top plug only really gets splashed, no significant pressure there.
 
#141 ·
marco_polo said:
The lower plug is certainly recommended/best practice, you'd be a very sorry boy if that one let you down.

£12 well spent (imo), vs hundreds in a recon box + labour. The top plug only really gets splashed, no significant pressure there.
Apart from the washer I see no reason to change it, but the washer doesn't seem available on it's own. I also find it odd that they've used an alloy plug, seems odd to have a potentially delicate thread
 
#148 ·
Sorry to revive this topic, guys, but it might be helpful for others also. I have an 120d 177cp FL, manual gearbox, and I am looking into changing the oil, though I don't have any problems with my shifting, except the 1st gear, which is an old problem. What oil do you recommend from your experience to put into the gearbox/ maybe diff oil also? I read that the fluid might affect your consumption/performance? I don't get this part. Thanks for helping and sorry for the noob questions.
 
#149 ·
Not sure what to suggest for your particular car, but if the oil you replace it with is thicker, then your fuel consumption would increase, as there's more "drag" on the gears. This would also affect performance, reducing power to the wheels, but not by enough for you to really notice with your butt dyno, unless you put tar in there.

Likewise, if the oil is too thin then it might not provide enough protection to the gears, so make sure you get the correct grade if you do change.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top