It could be a valve body problem, or a leaking internal seal. Contact your dealer, they might have a service bulletin with that concern.
〉 Answered on Jul 30th, 2008 by Donna Burmeister, Service Manager at Classic Nissan
Sounds like you may have a transmission problem. It could be as easy as being low on transmission fluid, or it could be a lot more complicated. The proper way to check the transmission fluid level is to have your vehicle up to operating temperature, parked on level ground and in neutral with the engine running. If you are going to check it yourself, make sure you have your parking brake set and be very careful of reaching into the engine with it running. Many parts will be very hot and there will be moving parts you need to be aware of (fan, belt etc.) If the level is fine, you will need to bring your vehicle to a qualified technician for a proper diagnosis.
〉 Answered on Jul 30th, 2008 by Suzanne Grego, Technician at City of Philadelphia Fleet Management