Mismatched tires are a common cause of premature transfer case failure on AWD vehicles.
In this Inside the Brands episode, CRP Automotive explains why all-wheel-drive transfer cases, including those used in BMW xDrive models, often fail due to factors outside the transfer case itself.

Transfer cases balance RPM differences between the front and rear driveshafts. When vehicle owners replace only two tires instead of all four, differences in tire circumference create a constant RPM mismatch. The transfer case compensates by working overtime, which can overheat and degrade the transfer case fluid.

Because many AWD transfer cases hold only about one liter of fluid, overheating can quickly lead to fluid breakdown, internal wear, and eventual transfer case damage, even when the correct fluid is used.

To help prevent premature transfer case failure, technicians should recommend:

1. Replacing AWD tires in sets of four, not two

2. Checking transfer case fluid at every service interval

3. Regular transfer case fluid changes, especially on high-mileage vehicles

For BMW xDrive applications, CRP Automotive recommends Rein TF0870 transfer case fluid, which carries BMW approval and also meets specifications for select Porsche applications.
Part No. FLDF002

This video is designed to help technicians reduce repeat failures and avoid costly AWD transfer case repairs caused by mismatched tires.