These are taken from the marlin crawler 4.7 gear instructions. These two things need to be clearanced in order for the gears to clear them becasue then ew gears are larger. You can look in throught the shifter hole and see if these have been clearanced. If they are then the case has aftermarket gears. But it won't tell you what kind of gears it has.
Step 49: Using a grinder or file, remove inside radius on shift forks(s).
Step 50: Top shift case only. Using a grinder, clearance shift block as shown above.
