Just put a new sink in and was not lucky enough to have the plumbing line up. I have it roughed in and wanted some insight/opinions on whether this will work, or what I need to do to fix it. I have a slope leading from the disposal to the trap, but with the new larger sink, my p-trap is about 2" lower than it previously was. I used a J-bend to meet the drain tail piece to the drain tube. It seems like I am fighting gravity a bit too much now as the distance between the p-trap and the drain tube is quite large. Will this setup work or do I need to approach it a different way? 
Plumbing – Is the sink P-trap too low
p-trapplumbingsink
Related Solutions
All traps need venting in all cases. Without a vent, the water seal in the trap gets sucked out and sewer gases can enter the room. There's also all sorts of examples where someone thought they were providing venting, but done in such a way that clearing the water seal was still a possibility. Some of these methods even used to be accepted practice, such as S traps. There's still several appropriate ways to achieve proper venting. For example, in island sink situations, a loop or foot vent is acceptable.
It's hard to say why the previous installation worked without venting. For sure, one way or another, the siphon action was disturbed by the entrance of air somehow, either from oversized pipe or leaking fittings. Regardless, where do you go from here? The downward facing ell in wall needs to be replaced with a sanitary tee for starters. The top of the new tee needs to tie into a vent somewhere, without travelling downwards. Is there a vent pipe nearby, such as from a toilet or shower? Or a pipe could perhaps be extended up into the attic, where it should be much easier to make a run to a vent pipe?
If all that sounds like too much, get a mechanical vent such as jberger suggested. They are not accepted by many codes, but they do work. Just be sure it's attached to a long enough pipe so that the valve is above the flood level of the sink. No doubt this all sounds like a real PITA right now. Once it's all done, you can take pride and sleep well knowing you have a properly functioning and completely sanitary sink drainage.
I ended up following Alaska Man's advice and lowered the sanitary tee. After installing the new sink and the disposal, it was obvious that my only option was to take the sanitary tee route. The good news was that I did have access to the other side of the wall so getting at the tee was simple. The unfortunate news was that I really only needed to lower the DWV about an inch.
Here is what my disposal looked like after install - showing the DWV too high by just a bit. The after shows how far I lowered the DWV.
On the other side of the wall, this is where I lowered the sanitary tee about 3 inches total.
Best Answer
Bring your Ptrap up or your Sanitary Tee down.
AS noted by others you can cut the tail of the piece where it goes into the top of the Ptrap shorter ( thereby bringing the Ptrap up ), This will allow you to have the down hill slope you need for the disposal. You may need a longer tail piece from the bell on the basin into the tee from the disposal.
OR
I think this is the better option because your sanitary tee is a little too high.
You could cut your drain pipe shorter so the sanitary tee is lower.
Use a regular Ptrap ( non flexible, there is no need for the debris catching flex connection here ).
You also need to mount your air admittance valve properly. It is not high enough, put it as high up as you can in the space between the bowl and the back of the cabinet.
If you put it on a threaded connection just above the san tee you will be able to pull it out to change it if necessary.