If your Ford had a Matthew McConaughey, it would be a Lincoln

Simply Serviced: BMW 135i Manual Transmission and Differential

A common sentiment from the uninitiated is that BMW’s are “difficult to service and expensive to maintain.” Now, sure you have to remove the bumper, intercooler, and various ducting to reach the radiator, but by and large, the basic stuff could not be made any more simple.

This car has the easiest engine oil and filter changes imaginable. The filter is front and center in the engine bay, in a housing that catches any loose oil in the filter when you remove it, easy and mess free.

To put it in perspective, changing the oil filter on my Honda Civic Si (or pretty much any four cylinder Honda), you have to remove the passenger-front wheel, remove the fender liner, and jam your hand between the axle halfshaft and the control arms while relying purely on wrist strength (because no tools can fit in there) to get that sucker out.

Let me preface this by saying the following: Yes manual snobs, this car has a true, three pedal, 6-speed, DIY gearbox. It’s great. I’m a manual-trans diehard and will never give it up in any of my cars.

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Back to the show: When it comes to servicing the manual transmission, people on the internet forums make a big fuss about limited access, and difficulty of refilling the transmission once the old fluid has been drained, blah, blah, blah. It can’t be that bad.

Transmission Fluid

Like most manual gearboxes, this one has a drain and a fill plug. Started off by breaking the fill plug loose first, just to make sure I could actually remove it, before draining all the fluid out, and then being screwed. The drain and fill require the use of hex/allen keys, which is...different. No real comment here, not better, not worse, just different to a typical Jap car. The fill plug came out with no fuss.

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Anywho, break the drain plug loose and make it rain:

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Manual transmission fluid is like really heavy motor oil, so let’s give it some drain time.

Well, what else is there to look at while we’re under here?

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“Yup, that’s a suspension, alright. Man, I forgot how close these fat tires and wide wheels are to the strut. I wonder exactly how close it is...”

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One 5 mil spacer later, and I know this: it ain’t that much. The spacer wouldn’t fit between the tire and the strut, so I’m guessing about 2-3mm of clearance. This is what those hellaflush kids are after, right? a 255 section width track day tire, seems pretty StanceNation to me.

Alright, the trans fluid hath stopped it’s flow. Drain plug pops back in place with roughly 15 ft/lb ot torque, as tested by my well-calibrated left hand. Time to refill. Taking some tips from previous MTF changes in other vehicles, I took the liberty of buying 5 feet of 5/8” clear tubing, duct tape and a small funnel beforehand. If that sounds like your idea of a good time, we need to party together.

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SHAMELESS PROMOTION: I’m a big fan of Redline gear oils. I’ve used their product in previous vehicles with excellent results. The gearbox is getting MTL and the diff is getting their 75w-140 diff oil, as recommended by the manufacturer of my LSD.

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Time to continue this back-breaking labor. Oh wait, this has only taken 10 minutes, 5 of which included taking pictures and wondering why the Internet seems to think this is so complicated. I don’t think they used enough duct tape.

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Duct tape your funnel to the tubing, and snake it down the engine bay, and into the fill hole of the trans:

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Make a few little adjustments to make sure nothing is going to knock the tubing out of the trans, and boom! We are in business.

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Treat the red liquid like wine at a Greek garden party and pour freely. After about a quart-and-a-half, gear oil was beginning to dribble out of the fill hole. Thread the fill plug back in, check for leaks, and we’re done.

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ELAPSED TIME: 30 MINUTES.

Differential Oil

Okay, I’ve almost considered breaking a sweat. I took a break to lubricate myself, with my preferred beverage of choice, Diet Coke (also shameless promotion).

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Time to service the diff. I now had about 2000 miles on the new limited slip diff, and MFactory recommended changing the diff oil after “break-in.” Eh, seems like as good a time as ever.

Hoist the rear of the car up as well and examine dat posterior, as the kids like to say.

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The 1-series and E90 3-series diff housings only come with a fill plug, as BMW intends the differential to be a “lifetime fluid.” With a stock open diff, sure, why not. But, this ain’t the stock life, kid, we modified now.

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This is another gripe on the forums, no drain plug; diff tricky to work on, etc., etc. Of note is that the diff plug is also hex, like the trans, and I believe it’s the same size too. Call that a 2-for-1.

I cut off about 12” of tubing from that 5’ I used earlier and attached it to a garage-use only turkey baster, and extracted the fluid out:

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Now, I know this is terrible way to analyze the oil, but the coloring seemed off, and it smelled like it was ready to be changed. No scary metallic bits or glitter in it, so I must’ve done something right.

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Rinse and repeat this process a few times, moving the tubing around the diff housing and gears of the diff to get as much fluid out as possible. After about 10 minutes of this, I deemed it sufficient.

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Work smarter, not harder. This $5 generic dispenser nozzle can be bought at any big box autoparts store, stick it on the diff oil case and pump away:

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With the stock open, the diff capacity is billed at 1 liter. I’m not sure if the LSD is larger than the stock open, but I only filled about 0.5L until the fresh oil started flowing out of the housing. I pulled the tube out and looked inside, and the housing was full up. Maybe I just sucked (heh, puns) at getting the old fluid out, I dunno. In any case, this is so easy I’ll likely change the fluid annually, if not sooner, so no harm, no foul.

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STOP THE CLOCK!

ELAPSED TIME: 30 MINUTES.

——

TOTAL TIME: 60 MINUTES

Keep in mind, I was taking pictures of the whole process, and spending copious amounts of time wondering why anyone would think this is difficult. I’m pretty sure I could knock this whole process down to about 30 minutes if I spent less time being a snarky jerk, but then, what sort of BMW driver would I be? Certainly not a very good one.

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I remarked on a Facebook post (you should totally “like” my page, it’s about as popular as I am funny) that this process reminded me of how enjoyable a simple service can be. In terms of seat of pants feel, it feels no different before and after, which is, I suppose, a good thing. The LSD still locks up nice and smooth, and the gearbox does it’s typical bang-bang gear change without drama. Most importantly, there was piece of mind two days later, when I beating on the car like it owed me money at the track, but that’s a write up for another day.

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