I ordered a gear for my VSS to calibrate the speedometer for the 3.73's. They sent a 21 tooth purple AOD one. I have a manual, will this one work or shall I send it back?
I don't think cutting the tip off will work. Upon further investigation I also noticed that the teeth on the AOD gear are longer so there may be fitment issues. I also don't know the effects of cutting the tip since it would no longer be capped off at the end. I think you would be better off just getting the correct gear.
The stock range of speedo gears work correctly with a limited range of tire sizes. The 23 tooth white gear works good for some guys, but self destructs in a few months for others.
Check to see if there is a speedometer shop in your area. If there is, ask about the Stewart-Warner speedometer gearbox. I believe it is either a 777 Series Drive Joint Kits and Parts or 666 Series Drive Joint Kits and Parts. It is a small gear box that fits between the speedo pickup gear on the transmission and the speedometer. It has quick change gears that allow you to choose almost any tire size and rear end gear ratio you want. This will allow you to get the accuracy within 1%-3%. The drawback is that it isn't cheap.
Please excuse the typo (their's, not mine) in the following picture - it should read Custom ratio adapters, not Custom radio adapters.