The "MegaRange" gearing is not really any greater than normal, it was a low of 11T or 12T and a highest of 34T gearing, which was common then and now.
Originally Posted by toker_ace
Does a mega gear freewheel require a special derailler? I'm having problems with my derailler on a mega gear freewheel i put on. thanks
The "Mega Range" is an older/cheaper Shimano cassette setup that had a particularly wide jump between the largest and second-largest cogs. It looks visibly different
than most other bicycle clusters and freewheels.
This Sheldon page shows them disassembling one:
The Shimano Mega 7 Freewheel
If this is what you have
, then it appears that there may have been a particular derailler for it.
This Amazon page:
Amazon.com: Shimano RD-TX51 Tourney Mega Range Rear Derailleur 6/7 Speed Hanger Mount Black: Sports & Outdoors
has a (Shimano) Tourney derailler branded as "MegaRange",,,,, -and I know for a fact that all Tourney deraillers are not
branded as "MegaRange".