Noise in Fourth Gear

WARNING: This page is about a different car, the 2010 GMC Sierra and 2010 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.

Checks	Causes
Sun Gear Thrust Washer 1st 2nd and 3rd Position	Inspect for wear or damage.
Input Shaft Thrust Bearing (60)	Inspect for wear or damage.
4th Clutch Hub Assembly	Inspect for damaged or worn 4th clutch backing plate. Inspect for improper selective 4th clutch backing plate retraining ring.