Combine soy sauce, balsamic, pepper, olive oil and wings in a large, zip-top bag. Close bag and refrigerate 4 hours to overnight.
Preheat an outdoor grill for medium heat.
Remove the chicken wings from the marinade and pat dry. Cook the wings on the preheated grill, turning occasionally, until the chicken is well browned and no longer pink, 25 to 30 minutes.
Place the reserved marinade in a small sauce pot set over medium-low heat, and gently simmer until reduced by half, approximately 5 minutes.
Place grilled wings in a large bowl. Drizzle with reduced balsamic marinade and toss to coat well.