A glider kit is a new truck cab/front axle/frame assembly which is used to economically rebuild a wrecked road tractor unit.
When a big rig is in an accident, often the only major component which suffers substantial damage is the cab. While it is possible to find used truck cabs, sometimes the cost of acquiring one can be prohibitive. The labor to break it away from the entire tractor assembly plus the shipping cost to the end user can total thousands of dollars. After all that work and expense, you still have a used truck cab which may have its own inherent problems.
One solution is to purchase a glider kit. This is a new cab, front axle assembly, and frame rails to which is added an existing engine, transmission, and rear ends thus making an entire tractor ready for the road.
The glider kit comes complete with new interior, sleeper compartment (if so configured), and new instrumentation/wiring.
The demand for glider kits is rather limited. While most of the major components such as engine, transmission, clutch, drive shaft, and rear ends are made by companies other than the truck manufacturer themselves, the cab design is specific to each brand. For example,almost every truck manufacturer in the US offers a Cummins diesel engine, but only Freightliner offers a replacement cab for their truck models.
A drive through many large truck dealerships will display dozens of complete road tractors. Chances are, tucked away in a corner, will sit one lonely glider kit waiting to be used as an economical solution to rebuild a truck.