* Chain Stretch/Wear: This is perhaps the most frequent issue. Over time, the chain that drives the output shafts stretches and wears. This results in a whining noise, especially noticeable in 4WD, and eventually can lead to slippage or complete failure.
* Low Fluid Level/Contaminated Fluid: Low transfer case fluid leads to premature wear of the chain and gears. Contaminated fluid (from leaks or improper maintenance) accelerates this wear process. Regular fluid changes (every 30,000-50,000 miles, depending on usage) are crucial.
* Shifting Problems: Difficulty shifting into 4WD high or low, or experiencing a grinding noise during shifting, points towards problems with the shift motor, linkage, or internal components. This could be due to wear, broken parts, or binding.
* Leaking Seals: Seals around the output shafts and case can wear out, leading to fluid leaks. This, again, accelerates wear and can cause further damage if left unattended.
* Bearing Failure: Internal bearings can wear out due to lack of lubrication or excessive stress. This manifests as noise, vibration, and ultimately, failure.
* Motor Problems (Electronic Shift): If your Tahoe has an electronically controlled transfer case, the shift motor itself can fail. This prevents shifting into 4WD.
* Chain Case Failure: The chain case itself, a housing for the chain, can crack or break due to age, stress, or impact.
* Vacuum System Issues (Some Models): Some older models use a vacuum system to assist with shifting, and problems with the vacuum lines or actuator can lead to shifting problems.
In short: Regular maintenance, including fluid changes and inspections, is key to preventing many of these problems. Ignoring noises or shifting difficulties can lead to expensive repairs. If you suspect a problem with your transfer case, it's best to have it inspected by a qualified mechanic.
