Grizzly Locker GM 14T, 40 Spline P/N YGLGM14T-3-40. The Yukon GM 10.5 14 bolt Grizzly Locker is a mechanical locking differential and is often compared to the GM 14 bolt Detroit Locker. It features 8620 internals for maximum strength. It's patent pending design reduces common locker failures. All units assembled in the USA!