Owners of four-wheel-drive General Motors pickups from 1997 to 2010 should all be aware of the dreaded "pump rub" issue. It doesn't matter if you drive a Silverado 1500, Sierra 3500, or even an Avalanche, if your truck has a transfer case, this story is for you.
In short, the pump rub issue refers to when the fluid pump inside the transfer case wears a hole in the case itself. GM transfer cases use a gear-driven pump inside the case that is driven off the mainshaft. Because of this design, the pump must "float" in the rear case half. There are four tabs around the edge of the pump that are used to locate it in the housing. GM installed a steel spring clip in the housing to try to prevent wear, but over time this clip can itself wear out or even break. This leads to the aluminum pump wearing through the softer magnesium housing.
The resulting hole can cause a very small leak. Because of the pump's position in the case, this leak is typically quite high on the case, meaning that it only leaks when the truck is in motion and does not leave a telltale puddle under the truck. Ultimately, afflicted trucks will run the transfer case dry of fluid before the owner has any idea that something is wrong.
Thankfully, there is a solution. PPE Diesel offers a kit that comes with a new pump housing cover, transfer case to transmission gasket, and threadlocking compound for less than $70. This new pump cover is machined from billet aluminum and features much larger locating tabs. This removes the need to use the factory spring clip and effectively prevents the dreaded rub from occurring, potentially saving thousands of dollars in repair costs.
The task is pretty straightforward for anyone with a bit of mechanical ability and takes just a few hours from start to finish. In addition to what you'll find below, there are many great videos on the internet that walk through the process in great detail.