toilet vent-suction-gurgle issue

[SteveLoewenthal]

I have problem where flushing toilet 1 gurgles toilet 2.
Toilet 1 and 2 are on different drain stacks entering into the crawlspace.
Toilet 2 is Y'ed into the drain about 10 feet downstream of toilet 1.
There is no vent between the crawlspace trap of toilet 2 and where it Y's in to the drain line downstream of toilet 1.

I think I have a possible solution but want advice from those that know more than I do. (I am an avid DIYer but hopefully humble enough to know that I sometimes need help.)

I am considering fixing this in the crawlspace as follows:
Add a T a little after the toilet 2 trap, a 2nd T 10 feet after the Y, both face up, and connecting them. My hypothesis is that air can flow between the 2 points while the water is between them.

This will take some work so I want comments before starting.
Any chance this will work? Any other suggestions are most welcome.

 

[Deerslayer]

I can think of multiple issues that could cause this, I rarely see venting issues cause this, if it was installed Poe code and inspected that makes it even less likely it's a venting issue.
Just curious did you say trap in the crawlspace under the toilet?

 

[SteveLoewenthal]

I did say "trap" but that was a mistake. I should have said "elbow" in both cases in the original post.
(should I edit the original post?)