Hey all,
This is the first interesting technique problem I’ve run into in awhile. I’ve had a in person bass teacher for a bit now and he finally decided to talk “Thumpin” with me 
He suggested I try to get my left hand dead slaps sounding identical to dead thumb slaps on E string.
Mostly getting weak buzz string sound rather than a deep sound, power coming from my forearm/wrist. Anyone have some pointers to get the same throaty hit as my playing thumb does?
Check the string height and position you tab the left hand. Usually I aim to hit the fret with both my left middle and ring finger as it adds more power and speed.
It usually serves a percussive ghost not to the Triplett you got going on with your right hand. Check out Stu Hamm video, he’s really good at this method.
Do you mute with right hand when you strike with left or get all the sound from left?
No the left hand is doing the muting as it supposed to be a short ghost notes. If you are doing left hand tapping then it depends. But usually you don’t tap and slap until your Kung fu is way up then it doesn’t matter, lol.
+1 to @Al1885 's response also.
When you slap with the left hand it really helps to have:
The fretboard strike is a lot like the thumb strike - it has to be quick, and loose. You have to let that hand bounce off the strings, like the thumb does… but - the tricky part - you can’t bounce off all the way or it will just ring.
My solution to this is to leave my index finger over the strings and to strike that fret-hand mute with my other three fingers. That way I don’t get the open string ringing out.
When I was just going through tunes where that technique is used, that’s what my hand is doing most often.
I am very tired, so I’m not sure if this is making any sense.
I hope it is!
Thanks a couple things in your explanation have gotten me more squared away. Like everything else control is very important!