The Y11 model came with several engine variants, predominantly from the QG engine family. Knowing your specific engine code is critical for sourcing the right parts.
The service manual dedicates 15 pages to the and the vacuum switching valves (VSVs). Before you replace the entire transfer case for $800, the manual tells you to check the vacuum hoses behind the battery tray. Nine times out of ten, a rodent chewed the tiny 3mm hose. Fixing that costs $0.50. Nissan Ad Wagon Y11 Service Manual
Nissan printed these on high-quality, durable paper. You can find used copies on eBay Japan or Yahoo Auctions Japan using the Japanese search term: 日産 ADワゴン Y11 整備書 . Expect to pay between $200 and $400 for a mint condition two-volume set. Be warned: They are entirely in Japanese, though the diagrams and numbers are universal. The Y11 model came with several engine variants,