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      11-03-2012, 10:02 PM   #129
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acthad's Avatar

Drives: 14 228i MSport Step
Join Date: Oct 2009
Location: Chicago

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e90 Trans Flush Service DIY Tips

So I just test drove my car after the job earlier, and got back to my house and put it back up on jack stands to check for leaks. AND there were leaks! !@#@#$!!!

So things to watch out for, use a high quality lightweight torque wrench so it is easier to handle for smaller guys like myself. I checked the pan's torx bolts 2X before, but after a heat cycle in the oil pan, 3-4 bolts were loose! So I torqued the torx bolt via the tightening 'star' procedure per ZF's instructions for a 3rd time with my heavy Harbor Freight 3/8" drive torque wrench and 6in extension and the T40 Torx socket. It is PITA trying to brace the torque wrench upside down on the garage floor! But after a 3rd time, it no longer had leaks.

My fill plug was also leaking, I could not tighten further before my test drive, even with the open ended wrench on it for leverage. But after the trans was hot from the test drive, I was able to tighten the fill plug (without leverage) until it made a creaking sound of being tightened. (I had the same sound when breaking the bolt loose in the beginning of the diy. I noticed my fill/drain plugs on my e36 manual trans work this way too.)

Also don't use ramps to elevate front of the car and jack stands in the rear. For some reason my front wheels had enough slack in them, even while in Park, or I did not realize even an xi in park is the same as a rwd e90. I jacked the rear up, the car gets pulled back so it could roll off the ramps! So 4 jack stands only for this job.

The exhaust trans bracket where it braces the 2 exhaust pipes with a double tube clamp gave me trouble. I removed this to get better clearance to the fill plug on top of the trans. It had a one time use bolt that snapped when removing the bolt that holds the bracket for the exhaust pipes. It had loctite from the factory, and the bolt is designed to snap off for removal. I ended up chiseling the broken bolt out from the threaded hole, then had to retap it for 8mm 1.25 pich thread bolt. Found another M8X50 bolt at my local hardware store, with a 13mm bolt head, and used this with loctite on the head vs the threads so I could get a chance to undo this bolt again if necessary.

Buy extra trans fluid if you had a known leak.

Be careful with the lifetime trans fluid, it has a strong odor, and will not come off your clothes.

The trans does not have to be scalding hot like it is during the summer in order to open the fill plug and to fill the trans. The trans never got hot for me and was cool to the touch vs warm/hot, the exhaust was way hotter. 10-15 minutes during the fall is sufficient.

It is a messy job, so it is not a bad idea to buy a Pig Mat for under the car to protect your garage floor. A pack them are $3 from Advance Auto.

If you need tools, check out for the 8mm Allen Wrench and 10mm Socket if you do not have tools, they have everything you need for less.

Hope this helps another novice weekend transmission mechanic out.
Current: 08 M3/4/6MT, Jerez/Black Novillo, CF, Premium, CA Winter, Tech, EDC, 19's

07 X5 Black Sapphire/Black Nevada Leather/Burl Walnut Premium, Sport, Adaptive, Active Steering, Nav, Comfort Access, Cold Weather I/II, CD Changer, Adaptive Xenons, Style 211s