Gray water vent

[Camping General]

Just picked up my trailer in January and had it out twice since the weather has warmed up. I am having a problem with the gray tank, though. I can only get a few gallons to drain into the tank before the water backs up in the sinks. After reading a few posts here and a few experiments in the trailer, I've concluded the vent must be clogged. I can fill the gray tank full from the kitchen if I remove the water from the p trap in the bathroom sink and let it vent there.
Anybody have any suggestions? The vent through the roof leads directly into the black tank. (I tried using a snake, then a garden hose. The black tank was the only one filling up). I guess the gray tank must T into the black vent somewhere.
Is there a plumbing diagram somewhere that would help me find where to access the vent?
Any help would be appreciated.
Thanks,

[Stan]

It sounds like the work you have done is sound and it DOES sound like a vent issue. Can you take it back to the dealer for warranty repairs? It could be anything from No vent to a plugged vent or something else.

[harley]

You should have a 'false vent' under the kitchen sink. It has a one way rubber check valve. It could be plugged or not there.

[Camping General]

Contacted Crossroads service and they suggested that I let the Dealer handle the repair. Scheduled an appointment and will see how it goes. I was really hoping to fix it myself since the dealer is about an hour away from my house. That means dropping it off on Saturday, leaving it all week, and picking it up the next Saturday. (Assuming it is fixed)

[TxCowboy]

Would CR authorize a mobile tech instead of hauling your RV to the dealer? The service tech fee is worth paying NOT to have to haul the RV around, IMHO.