Phil,
I thought that we were talking about the tail bevel gears, not the auto rotation gears or front TT drive gears?
I'll try to tell the whole story....
- All the tail bevel gears are dimensionally the same and directly interchangeable black or white, you could even use one black and one white if you wanted. Only black gears are available now. Align part #H60G003XXT
At the front it's a bit more complex:
Align have two different tail drive ratios fitted to different versions of the 550e:
- Option 1 (4.5:1 drive ratio, as fitted to earlier 550e V1 and V2): 180t M06 auto gear which has to be used with the 40t M06 front TT gear set. These were originally white but have been replaced by black gears which are directly compatible. Align part # H60020AAT for auto gear and H6NG001XXT for the front TT drive gear set.
- Option 2 (3.85:1 drive ratio, as fitted to later 'pro' versions of 550e): 131t M08 auto gear which has to be used with the 34t M08 front TT gear set. These were also originally white but have been replaced by black gears which are directly compatible. Align part # H60198QAT for auto gear and H60G002XXT for the front TT drive gear set.
The earlier type (option 1) gives a faster tail RPM and better suited to lower or moderate headspeed, option 2 is better for very high RPM ( for 3D nutters). It is possible to retrofit either drive option to any version of the 550e providing you replace both auto gear and front TT gears as a set.
It sounds like your dealer was trying to match option 1 and option 2 parts, which are dimensionally different and so cant be mixed. The colour is not the issue, it's the number of teeth and the module (or 'M') number that determines if they fit. Both option 1 and option 2 were originally made in white plastic then replaced by black. For years I ran a white auto gear with a black front TT gear, no problems at all because they were both 'option 2' components. For both drive options only black is available now.
Trust me on this, my 600 uses all the same parts and the tail drive gear options is something that causes confusion again and again. I hope the above all makes sense.