E46 M3 SMG gearbox issue

[Imola]

Recently I had a problem with my SMG gearbox not selecting gears and after some good advice from Ian (Alpina527) and the local Indy it appeared I needed a new box. I located one as my warranty has expired and got the local indy to fit it, as the box was out the clutch was also replaced.
After fitting I got my old box back so I can sell it on to a refurb specialist. So with the latest software now on I'm back on the road. My only concern is that when I looked at the old box and parts I found a cable had melted, anyone any ideas what it is and may this have been the problem from the start ? BTW the car was not visually inspected prior to me getting the new box only driven as everyone confirmed you don't strip and repair the smg box just replace it. I may have rushed into the repair as I just wanted the car back on the road.

http://i4.photobucket.com/albums/y107/duds001/DSC01106.jpg

http://i4.photobucket.com/albums/y107/duds001/DSC01107.jpg

http://i4.photobucket.com/albums/y107/duds001/DSC01108.jpg

[Chaos]

That looks like where the temperature sensor goes, which may or may not have been a problem. However it's also really close to where the crankshaft speed sensor goes, which probably would have given you issues with gear selection if it needed a signal back and wasn't getting one.

From memory I can't remember which is which, I thought they went one above the other not side by side, and I'm not convinced that I'm entirely correct in identifying the parts, but I'll have a think and see what I can dig up later on when I have some time. Curious to know exactly what it is, too.

Errrr ok hang on, brain fart time. I think that part faces the other way, and bolts on to the back of the box. In which case that black plastic box on the left end as you look at the pic is in fact the gear identification switch. If that's not getting a signal to it, or back from it, there's your selection problem.

Will try to find out for certain..

[Chaos]

Yup, it's the cable off the gear ID switch on the actuator assembly. More I look at it, the more I see it too. 99.9% that's your problem right there. Looks like there's a section of the cable missing though, they didn't cut/rip it off or anything to get the job done quicker did they? Looks fairly extreme given that there's no signs of rubbing or heat on the outside of the box where the cable would have been..

On a plus note, you could buy a new cable and socket then sell it as a working 'box, but it's a shame you didn't find that before you bought a complete replacement.

[Imola]

Thanks Chaos, my problem is I have no idea how or where the smaller piece comes into it, other than the cable has melted, and yes the wire has been cut, also the connector on the side of the box is melted, on the 3rd pic it's on the left lower side. Would the wire be visible before the box was removed. It may have had a dodgy connection hence the melt or possibly the exhaust may have melted it, I'm no expert at all so have no idea :o

I also have no way of knowing if the box is OK and to sell on as in working order. It would be nice if I could sell as would recoup some £££

[Chaos]

Yeah you wanna make sure before you sell it on as working, too, or it may come right back at you...

If the cable's been cut then it explains why it looks short. No doubt that the connector has melted in the socket, my only question is 'why'.. There's no sign of burning, no obvious signs of a hot spot there on any of the casing, and the socket next to it looks fine. Maybe there was some sort of short that fried the wire, but that's a bit of a big 'maybe' with nothing else to corroborate it.

The wire isn't really visible in situ. That box sits pretty much underneath where the gear lever and centre console are. I've never tried to look and see if it is visible, but it'd be pretty tight to see and you almost certainly wouldn't be able to tell that it had come adrift from the top as it's clamped just forward of the box (the rusty clip in the centre of pic 1). What would/should have been visible was that socket, though. That's right underneath the bulkhead at the bottom of the engine - you drop the lower cover off and that would be right in plain sight. Surprising that nobody checked there given the problems you were having. Maybe seems more obvious with hindsight, who knows.

Honestly, all you can really do is to sell it to a refurb place and show them the socket and explain what you've done before asking for top money as they don't need to refurb anything at all - just replace a socket and test. If the garage that diagnosed the issue have an opportunity to test-bed it for you then great, that solves a lot of issues, but I'd be very surprised if they'd have the ability to do that as it's a fairly specialised requirement.