It’s common for a drive axle to be vented to atmosphere to account for internal pressure changes as the axle heats up and cools down. The vent on the 2005 Corvette is unique.
A check valve relieves pressure as heat builds up. It’s set to open at 0.7 psi (4.8 kPa).
However, this vent doesn’t allow air back in during cooldown, to prevent water intrusion. As the air cools down, it can pull a vacuum of between 3 and 5 psi (20-34 kPa).
Consequently, is possible to hear a hissing sound when removing the oil plug. This is normal, and results from air entering the axle.
TIP: The sound may be mistaken for pressurized air escaping.
- Thanks to Dave Howe, GM TechLink, February 2005
General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.
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Article ID: 329
Created: July 17, 2014
Last Updated: July 17, 2014
Author: Rob Loszewski
Online URL: https://www.corvetteactioncenter.com/tech/knowledgebase/article.php?id=329