While there are plenty of AD series (AD4, 5, 8, 10 & 12) and Cloud Nine shocks still in use, we no longer manufacture small parts for those outside of seals kits and valve kits. Therefore, we can no longer offer a Factory Service option for these shocks.
Many times, an AD or Cloud Nine shock that is not holding air simply needs new seals and/or valve. AD-4 & 8 shocks are not serviceable. We do offer kits for AD5, AD10/AD12 and Cloud Nine directly on our Rear Suspension Parts & Accessories page under the "General" tab. Additionally, your local bicycle dealer that is versed in suspension can get kits and perform the service.
If replacing the seals and/or valve does not solve air leaks, then it will be time for a new shock. To help you determine what you would need, please refer to our Everything You Need To Know About Rear Shocks article.