First of all, I drive a 92 Miata, only mods are DFV Ohlins coilovers, 107k miles. I was on my way home the other day and it was raining. Starting off at a stop light my rear tires slipped no big deal, however, I heard huge banging sounds and it sounded like it was coming from the footwell? maybe... But it was lurchy and the transmission shifter was rocking from side to side pretty violently.. I tried to replicate the process and it only seems to happen when I intentionally spin the wheels. It had happened once before prior to coilovers and now with them installed happened much more harshly this time. I first considered it to be trans mounts, however after searching on here to confirm we only have engine mounts the ppf and diff mounts that shot down my idea. So thoughts? Thanks!

 

You are headed in the right direction. Get the motor and diff mounts checked as all of those vibrations and banging would transfer through the whole driveline.