While variable geometry turbochargers provide instant response at virtually any engine speed and can double as exhaust brakes, their moving parts are prone to failure. Due to being present in the exhaust side of the turbo, the vanes, unison rings and/or actuators are constantly exposed to soot, carbon and grime buildup, not to mention rust. All of the above can render the moveable parts required to function inoperable, which leads to poor drivability, excessive smoke and forces the issue of cleaning or replacing the turbocharger. Any VGT-equipped engine is susceptible to this type of failure, but in the diesel pickup realm it’s highly common on ’03-’07 6.0L Power Strokes and ’07.5-newer 6.7L Cummins mills, while still being fairly prevalent on ’04.5-newer Duramax applications.
The Solution:Long before VGTs came as standard equipment on diesels, fixed geometry turbos were used—and oftentimes they outlasted the life of the engine they were bolted to. This is exactly why handfuls of aftermarket companies sell direct bolt-on kits that replace the factory VGT with a fixed geometry BorgWarner or Garrett turbo. Void of the exhaust-side complexities present in VGTs, the mechanical functionality of a fixed geometry turbo is much simpler and—in most cases—a lot cheaper to overhaul or replace. Although some low-rpm drivability is lost by switching to a fixed geometry unit, the gains in reliability, performance and peace of mind far outweigh the cost of sticking it out with a VGT that could fail at any time.