Home » BMW Deleted The Fill-Plug From The i3 Leaving Owners With No Way To Change The Gear Oil: A Rant Against ‘Technical Cost Reduction’ And ‘Filled For Life’ Gearboxes

BMW Deleted The Fill-Plug From The i3 Leaving Owners With No Way To Change The Gear Oil: A Rant Against ‘Technical Cost Reduction’ And ‘Filled For Life’ Gearboxes

Bmw I3 Gear Oil Plug Ts2
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“The first model year is the one to avoid,” is the conventional wisdom about when to wait to buy a car and when to pull the trigger. In reality, things can be more complicated than that. Take my BMW i3, which I bought because it was cheap due to it having 135,000 miles on the clock and being the first model-year, 2014. These early i3s suffered from all sorts of first-model-year growing pains, but you know what they didn’t suffer from? Bullshit Technical Cost Reduction (TCR) like removal of a fill-plug, justified via the concept of “Fill For Life” transmissions. Let’s talk about this.

If you pop the hood of an automatic car from the 1990s, you’ll most likely see a second dipstick to allow you to check the transmission fluid quality and level. Move on to the 2000s, and you may have a fill-port on top of your transaxle, along with an “overflow” plug down below telling you when the transmission is full. Check underhood of a modern automatic-equipped vehicle — even an off-roader like the Jeep Wrangler JL — and you’ll see no dipstick at all and no fill port. That’s because modern automatic transmissions are what’s called “fill for life” transmissions.

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Basically, the automaker (and transmission manufacturer) decided that, given the driving conditions the vehicle was designed to withstand, the transmission will last however long the automaker determined is the life of the vehicle. I’m sure this involved lots of life-cycle analysis and looks at warranty data, with the conclusion being: “It’s honestly just better for warranty costs if people just don’t mess with their transmission.”

I’m not saying this is unsound, as I’m sure it’s backed by loads of data. What I am saying is that I hate the whole concept of being unable to drain fluids that are actively suspending more and more wear particles with every mile I drive, and that could become contaminated under certain conditions. Take my 2014 BMW i3. It’s got 143,000 miles, or way, way more miles than any automaker’s differential fluid change interval from just a few years ago. Yes, gear oils have changed, modern machining tolerances have improved, materials have become more advanced, and on and on. But here’s the thing: BMW i3s are failing their rear motor bearings:

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I cannot conclude that these failures could have been avoided with clean fluid, but the reality is that fluid cleanliness affects bearing life, and I don’t want my car’s longevity to be limited by by $20 worth of fluids. So I drained my oil and filled it via a 2014-model-year-only fill plug. Here you can see what 10 year, 143,000 mile gear oil looks like as it drains from my rear drive unit:

 

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As you can see, the fluid looks OK, but it’s not perfect, especially not at the bottom, where sediment has settled:

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Luckily, my drain plug is magnetic, so it’s picking up all the metal shavings associated with any geartrain wearing at a normal rate:

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Unfortunately, in early 2015, BMW deleted the fill plug from the drive unit. Why? Maybe to avoid incidences of folks filling it with the wrong fluid, but also maybe because it will save them a little bit of money per car. Here’s how much that fill plug costs to manufacture, per automotive benchmarking firm Munro & Associates:

 

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That’s 26 cents per car. BMW made a quarter million i3s, so we’re talking over 60 grand potentially saved (minus costs associated with making the change). But it’s not just the cost of the drain plug that’s being saved, it’s also the cost of the gear box cover, which Munro says costs BMW almost $18 to make; having that threaded hole there definitely adds to that price, so you can expect savings on the cover when that fill plug is gone.

And every penny matters to a “Technical Cost Reduction” engineer whose sole focus is to find ways to pull cost out of the production of a car in a way that — at least in theory — doesn’t negatively affect the customer. I guarantee some genius TCR engineer — whether at the manufacturer or supplier — asked “Isn’t our rear diff filled-for-life? Then why do we need a fill plug?” And before you knew it, the plug was gone.
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This leaves 2015+ BMW owners in a lurch, as many want to drain their gearbox oil for peace-of-mind. Listen to what owners of BMW i3s equipped with range extenders have to do to drain their rear diff oil, via  :

Apparently, BMW deleted the transaxle’s oil filler plug on BEV models beginning in 05/2015 and on REx models beginning in 04/2015. For models without an oil filler plug, oil must be added through the output shaft hole after removing either output shaft. Not very convenient! To me, this suggests that BMW doesn’t intend on the oil being replaced during the life of an i3.

Yes, they have to remove the halfshaft to add gear oil to their gearbox, and all because BMW removed a fill-plug to save a few cents! How frustrating! Just look at this poor bastard trying to do routine service on a post-2015 i3:

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Some folks have found workarounds. Non-range-extender i3s can use their breather as a fill-plug, but with the range extender, that’s impossible to get to, so many folks are — and no I’m not kidding — filling their rear differentials through the drain holeJust look at this madness:

They rig something up that allows them to seal the drain hole while pumping gear oil in, then they quickly remove their threaded contraption, shove their thumb over the hole as quickly as possible so as not to spill too much gear oil, then remove their thumb and quickly try to thread the drain plug back on. What a nightmare.

I, meanwhile, drained and filled my fluid in five minutes flat, with no mess. All because my i3 hadn’t been out long enough to be TCR’d to death.

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Now, it is worth noting that early BMW i3s are the ones most prone to bearing and compressor failure, according to BMW i3 experts, but I bought mine with 135,000 miles on the clock, so I like to think that the design weaknesses would have already reared their heads by now, and that at this point I have a nice, serviceable, relatively cheap, reliable car that that hasn’t been TCR’d to death. In fact, when I was debating trading my car for a 2019-2021 i3, a reader named Nick Nguyen sent me this:

Dude, keep the 2014. Did you notice the pile of cost reductions over the years? For instance, your giga wheels are directional forged wheels, they’re like a throwback to the 90s when Japanese bubble economy cars did separate designs for the left and right of the car. REx models actually have four distinct wheels for each corner due to the staggered setup. Also, the later models lose the handy net under the climate panel and some bungees in the rear. It is very easy to add carplay to an i3- since the display is separate from the brains of the infotainment, everything goes under the rear seat and it just intercepts the knob. Your 2014 also has the widescreen 1280×480 display that is so much nicer

Add to that the fact that I got a brand new battery in this machine, and I really feel like I scored the best of all worlds.

Still, I feel for those poor 2015+ BMW i3 owners.

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Donald Anthony Waters
Donald Anthony Waters
23 days ago

BMW is NOT a brand for people who like to work on their own cars. BMW has a factory recommended service to walnut blast the valves 75k miles and 40k after. They use aluminum bolts torqued to 40-80nm and then a 180 degree turn. Constantly breaking bolts trying to remove these. A crank bolt requires 80nm and then 360 degree turn, and this is for timing chain replacement. That’s probably upwards of 500 ft lbs. Absolute nightmare working on these things. Across all models.

Taxi maniac
Taxi maniac
24 days ago

Ah the old “change the oil through the drain plug with a swap-aru from fill hose to plug while oil is draining on you!”

Love that. Never done that one before.

You could put the car on a rotisserie and flip it upside down and fill it while the undercarriage is pointing at the sky too. Wouldn’t even need to crawl under the car then either

Freelivin2713
Freelivin2713
24 days ago

Yeah, this is the kind of shit that just makes absolutely no fucking sense…I don’t care how much they save…if there’s a fluid, any fluid…it needs a damn drain plug…PERIOD. Those TCR Engineers should be punched right in the face then forced to change every fluid in the car to see how it’s supposed to be done…after fixing the problem they created in the 1st place

Jalop Gold
Jalop Gold
24 days ago
Reply to  Freelivin2713

Oh, they have a drain plug. It’s the fill plug they still need!

Freelivin2713
Freelivin2713
22 days ago
Reply to  Jalop Gold

Oh yeah, that’s what I meant…even after reading the whole thing and the drain plug being mentioned constantly I still put it wrong…yeah, it was actually years ago when I first saw some of them got rid of fill plugs and I thought “do they not even have a brain?”…”There’s no common sense anymore” and “Now it’s for sure they’re doing this just to frustrate and piss us off”

Thomas The Tank Engine
Thomas The Tank Engine
24 days ago
Manwich Sandwich
Manwich Sandwich
24 days ago

I wonder how feasible it would be to drill/tap a new fill hole into the side of the transmission on the 2015+ models.

Tagarito
Tagarito
24 days ago

Metal shavings 🙁

Manwich Sandwich
Manwich Sandwich
24 days ago
Reply to  Tagarito

So you drill it, then drain/replace the fluid (or do it twice if you’re really paranoid) and let the magnetic plug screw take care of any remnants.

Last edited 24 days ago by Manwich Sandwich
Tagarito
Tagarito
23 days ago

Makes sense! So you can both have clean fluid and keep it clean

Dudeoutwest
Dudeoutwest
25 days ago

They did similar when they introduced the “hexhead” boxer motorcycle line in 2005. It was “lifetime service” or something in the final drive. Then, in 2006, they started having issues with final drive failures and did a bunch of redesign work that added a drain plug. Previously, you had to unbolt the final drive to drop the final drive so the only hole in the final drive, which was at a 3:00 position would point down to allow drainage. The whole is tiny, so filling it with the required hypoid took forever.

What is it with BMW and this kinda thing?

Hotdoughnutsnow
Hotdoughnutsnow
25 days ago

I burned up the transmission in my 2000 Wrangler because I never checked the fluid; there was no dipstick. You had to warm the engine, then remove the plug on the side of the transmission and stick your finger into the hole from underneath the hot Jeep. I didn’t even have the tool to remove the plug. 🙁

JumboG
JumboG
24 days ago

My BMWs both do a fluid check for the trans this way.

FrostyRam31
FrostyRam31
25 days ago

Let’s not forget about the labor savings in addition to the 26 cent plug. Once less part to track in the database, fewer manufacturing steps, quality checks, etc. I still think it’s a dumb idea to get rid of it, but they’re saving way more than 26 cents a unit.

JumboG
JumboG
24 days ago
Reply to  FrostyRam31

Yeah, what 35 or so cents?

Tangent
Tangent
25 days ago

What’s really maddening is the transmission manufacturer almost certainly does not agree with “lifetime fill”. All modern BMW automatics are labelled as lifetime fill, yet ZF who manufactures the transmission recommends changing the fluid every 8 years or 80k km, whichever comes first.

“Lifetime fluid” appeared at about the same time as free maintenance plans did. Between that, way too many consumers thinking “required maintenance” is barely different than “unreliable”, and even unserviced transmissions lasting way past the age that most first owners keep the car it’s really not surprising that they went with it. Following that recommendation is realistically just bad for the second, third, or later owner and most manufacturers really aren’t worried about what those people think.

Boulevard_Yachtsman
Boulevard_Yachtsman
25 days ago
Reply to  Tangent

Learned about this with my XK8 and its ZF transmission. It seemed funny to read in the owner’s manual about the “lifetime fluid” that a person can’t check, but then see a drain plug on the transmission pan underneath. Thankfully, it was only “kind of” a pita to get it back to it’s proper level – there’s a fill plug just above the exhaust. Of course, the fill procedure is supposed to be done when the transmission is warm, so that pipe is nice and hot by the time one needs to put the fill plug back in.

Tangent
Tangent
25 days ago

Yup, enjoyed exactly that scenario with the X3 I replaced the “lifetime” fluid on. I avoided burning my hand but the tube of the fluid filler I was using now has a nice little melted patch on it.

That One Guy
That One Guy
25 days ago

I’m sure the machining for the hole the plug goes into also cost at least a few more cents.

Maxzillian
Maxzillian
25 days ago

Reminds me of the 4L30E. Generally considered an unreliable transmission, but that’s certainly in part because they stopped utilizing a dipstick somewhere in the mid 90s. You were given an oil pan with two plugs, one at the bottom for draining at one a couple inches higher for filling.

The expectation is that you’re to get underneath the car while it’s running and after the transmission has warmed up, remove the upper plug, add oil until it runs out and reinstall the plug. For a DIY mechanic it sounds like hell. For a professional mechanic it’s a pain in the ass.

All one has to do is wait for the inevitable pan or shaft seal leaks and it won’t be long for this world.

DEcarTrouble
DEcarTrouble
25 days ago
Reply to  Maxzillian

Got one of those in my 2001 Z3. Car has 288k miles on it and I am 90% sure the fluid has been changed at some point, but it was not any time near when I bought it. When I cracked the drain open it was like black water coming out. Comparing viscosity of it to the fluid I put back in was night and day. I am almost positive that the torque converter is on its way out because of how long that fluid was in there, but it is running slightly better with the new stuff in.

Going to be replacing the fluid again soon to hopefully clean out more of the crap that was still left in the converter.

Maxzillian
Maxzillian
25 days ago
Reply to  DEcarTrouble

I just picked up a Vehicross that had a burnt band in it. Looking at all other potential causes the transmission looked fine and low oil was the best explanation I could come up with.

DEcarTrouble
DEcarTrouble
25 days ago
Reply to  Maxzillian

I mean it is not a great transmission, but given an even worse rep due to “lifetime” fluid. I don’t know if the transmission has ever been replaced in my Z3, but if it hadn’t then maybe we should rethink the 4L30 hate a little.

Maxzillian
Maxzillian
24 days ago
Reply to  DEcarTrouble

I don’t think it was ever referred to as a lifetime fill, but they made the process so difficult that it effectively was.

DEcarTrouble
DEcarTrouble
24 days ago
Reply to  Maxzillian

Maybe not for other vehicles, but the BMWs it was installed in are “lifetime.” Must people know that they considered the cars 80-100k miles as lifetime for the model years they were in.

Maxzillian
Maxzillian
24 days ago
Reply to  DEcarTrouble

Ah, I see. In the case of Isuzu it appears there was an expectation to check the level and change as required. I suppose that shouldn’t be too surprising since the usage of the transmission is totally different despite the internals being practically identical.

DEcarTrouble
DEcarTrouble
24 days ago
Reply to  Maxzillian

Yeah, that transmission was used by GM, Chevy, Isuzu, BMW, and a herd more from what I recall. Not sure how each handled the fluid changes other than BMW since I own one.

Shooting Brake
Shooting Brake
25 days ago

I’m going to keep this short so I don’t go into a full blind rage while typing it, but I hate this type of engineering you into failure/cost cutting bs so much.

Ok_Im_here
Ok_Im_here
25 days ago

I have a 2016 Mazda 6 with that supposedly does not need transmission oil change. It has a lot of mileage on it. Not sure what to do.

AlfaWhiz
AlfaWhiz
25 days ago

Let me offer a solution:

  1. Exit cars & coffee Mustang style
  2. Flip car upside down
  3. Refill oil using drain plug
  4. Success
86-GL
86-GL
25 days ago

Just drain the oil and flip the car over to fill it back up!

Matt Sexton
Matt Sexton
25 days ago
Reply to  86-GL

Came here for this, was not disappointed.

Boulevard_Yachtsman
Boulevard_Yachtsman
24 days ago
Reply to  86-GL

The patented BMW rotisserie service.

Josh O
Josh O
25 days ago

Seems to me someone with Engineering prowess could design a drain plug that could be removed with a socket then reinstalled and have a Schrader valve like fitting in the center that could push fluid in.

B P
B P
25 days ago
Reply to  Josh O

Maybe a Fumoto valve could work? https://www.fumotousa.com/f139n.html

CRX89
CRX89
24 days ago
Reply to  Josh O

Nissan’s smaller CVTs have a small threaded pipe in the pan, past the drain plug, that is removed to drain and when installed serves to set the level.

JumboG
JumboG
24 days ago
Reply to  Josh O

You just do it like a marine drive unit (sterndrive or outboard) – you drain the fluid, then remove the upper plug, Note the upper plug is not for refilling the fluid, it’s to let air out as you pump oil into the drain/fill plug until it start coming out the vent plug. Put the plug back in the vent hole. Then quickly remove the fill tube and screw in the drain/fill plug while oil is gushing all over you.

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