Tranny slippage in OD only
I just failed AZ Emissions Ck yesterday.
Not due to emissions.
Transmission slippage in O/D gear position.
Any other gear selections. No slippage.
I can hear a vacuum leak.
Sound adjustable by accelerator pressure.
When in Normal D position, that vacuum sound changes with normal gear change by thy tranny.
How can I troubleshoot that leak the simplest way?