Here in the passenger-car industry, the thought of buying a vehicle from one manufacturer and then specifying an engine from another is almost unthinkable. Granted, upon further consideration, such an arrangement could produce some highly entertaining results. Regardless, that's exactly the way things have been done in the heavy-truck industry, where the loyalty to a particular brand of engine is every bit as strong as - if not more than - one's affection for the chassis in which it's placed.
Even as the passenger-car industry becomes less vertically integrated (witness transmission development and manufacturing), the heavy-truck business has gone in the other direction, with chassis vendors bringing engine development in-house. This could leave manufacturers such as Cummins and Caterpillar out in the cold. Cummins in particular is said to be in potential trouble, as it doesn't have its own line of off-highway equipment like Caterpillar.
[Source: Reuters Asia]