Before I start the round-robin of buying and trying the wrong sizes...thanks in advance!
Should be the same for the 355, but you never know...A 17mm female socket wrench for opening your tranny dipstick bolt on the 348.
I presume that you want to remove the filler plug/combined dip stick on the upper surface of the gearbox casing of a 355 manual box; if this is the case, I needed a 12mm across flats male hex. As has been mentioned in other posts, this can be very tight. Some think it's the result of an electro-chemical reaction between the different materials (plug versus casing material). Others think that it might just have been there too long and/or was torqued too tight. Just learned a couple of days ago that (of course!) an option is (if I understood correctly) to fill through the breather tube. In any case, it's a good idea to apply some WD40 or whatever on the plug well in advance - might help (don't know if that helped, but after a few WD40 sessions, I crossed my fingers and shocked it off with an air gun). If you do finally remove the plug, it's a good investment to replace it with a new one. Good luck!
+1. Hit the plug with PB Blaster once or twice at least 24 hours before removal. Replace the plug with a new one and use a copper-based anti-seize. No more problems.
Thanks for the guidance and advice! I thought that this was something that my dealer would check during my recent service, but apparently not. Here's the list so far: 12 mm hex WD-40 or similar Prepare to need air/impact driver to break loose New plug Anti sieze compound Apparently not designed to be checked very often...
Maybe we need someone who has actually done this on a 355 to weigh in...because that very similar dipstick/bolt on my 348 is not meant to be screwed in tight. It's barely more than hand-tight when installed. Comes off *easily* when you put the socket over it. Meant to be checked regularly. Pop the hood, lean over, reach down with the socket, unscrew, examine dipstick, re-install, done. Takes seconds. I'd be *shocked* if 355s were seeing that similar dipstick bolt cranked down hard enough to get stuck over time. I'd be shocked if that tranny dipstick bolt was on (or supposed to be on) any tighter than the 355's power steering dipstick.
Both times I changed the gear oil in my 355 (and in my previous 328GTS for that matter), when I tried to loosen the fill bolt it was tighter than crap! Even when I KNOW I installed it and simply snugged it up good, just starting to compress the new copper crush washer. Not sure why that is....but now I just barely snug it up.
The fill bolt on the 348 is huge: 19mm! And yes, it gets very, very tight. The dipstick bolt on the 348 is smaller (17mm) and not tight at all. That being said, the fill/check bolts on the 308 diff get very, very tight. Those are female plug bolts that require male hex wrenches, though...and those are horizonal. The 348 and 355 bolts should be vertical!
Mine was tighter than (think something really tight, use colourful imagination if required) I think it was a 12mm (I can check if you like...) hex which I cut the end off and fitted into a 12mm socket and use a big bar with a pipe on the end of it....this thing really is tight. I have my gear oil changed every year during my annual service.
James, +1 And for No Doubt's sake, I did it with the engine out so I could play around with heating, shouting etc. As I said, it IS a 12mm male hex and like you I slotted it into a socket and gave it a big heave with an extension bar. Took air shock to loosen it in the end. IMO its the result of dissimilar metals creating a corrosion block. When putting back together I used a copper based grease and tighted to the specified torque. Let's see what happens next year!
Thanks, guys. Ronrob, could you clarify if the the 355 has two different parts, one a fill plug and the other a dipstick plug...or does the 6 speed tranny only have one part that does both?
James in NZ was out of bed before me to clear that one up! Have a nice day, or evening or night everyone!
