So Tuesday right after work I rushed home to start the reconstruction and reassembly of the instrument cluster of the BMW. Job one was to create a clean environment and to keep dust and contaminants out of the gear assembly to prolong to life of the gears I was replacing, especially since the original ones only lasted for 302, 075.1 miles.

So the first half hour was taken up with cleaning and dust removing in the area I was going to work, then I got the baggies with the two gears out, the 1st gear, the big 48 toother (still less than an inch across) went over its pin and merged with the gear under it with no problem, then came the tiny 1/4 inch 12 tooth baby gear that drives the entire works. The hole in the center of the gear was way too small. It would not even begin to fit over the small part of the pin drive it was supposed to go over (see the illustration I so thoughtfully made in photoshop for this explanation), I was miffed, mystified and maddened that the part described was not the one that arrived. I could call and order another one, but they closed at 7:00 EDT and it was 7:07 (just my luck) when this discovery was made. I thought for a bit, did I really want to wait another 3 or 4 days for a teeny tiny gear so that I could finish the job I was on? I hit upon an idea, I got out my Dremel tool and all the bits. I found one slightly smaller than the grooved larger area of the tiny drive-shaft, and I found an even smaller one that was the same size as the top part of the drive-shaft pin.
Making the larger hole was easiest, I first wedged a jewelers screwdriver blade into the hole, then locked that in my bench vice, then very slowly and carefully bored out the hole about 3/4 of the way (3/16th of an inch) into the gear. Next step, I had to flip the gear over, change the Dremel tool collett for a smaller bit size and bore out the other side. This was more difficult because I could not use the vise to hold it stationary while I worked (tiny brittle plastic gears in the jaws of the vice, no way) I improvised with a pair of 45° angle needle nose pliers, and worked with patience and my eyes about an inch away from the rotating bit, to keep it perpendicular and centered. With a bit of anxiety I carefully slipped the gear over the pin and delicately tapped down over the grooved shaft until the pin came out a millimeter from the top of the gear. It fit perfectly, I then hand turned the whole affair and watched as everything performed the jobs they were supposed to perform.

Back Home @ 8:57, after a test drive.
That done I cleaned the inside and out of the plexi and plastic gauge housing and re assembled that . Then came the reinsertion into the dash, the reconnection of the electrical components, just after 8:30, two hours since the physical part of the job began, I was once again on the road and the odometer was ticking off the tenths and miles as designed. Now, what to do next? I have front suspension upgrades to perform, and the e-brake to get operational too. More body work and sanding and finally a paint job. looks like a gear-heads work is never done.
Chuck Pace ©2009 
|