4t60 Slip/Shudder when starting out.

92 Cutlass Ciera 3300 V6 4t60(NOT electronically controlled) 174k

This happened overnight. Went out, drove car cold and starting out from a stop with 10%-30% throttle the car would shudder and slightly slip from 3-8mph. It won't shudder with less than or more than said throttle. Fluid/filter was changed in Feb at 150k-it's red and full, I added some lucas transmission fix and it cured the slightly harsh 1-2 shift under load but made little to no difference with the shudder/slip. I also adjusted the TV cable. No difference.

It's alot more noticable cold, but still present when hot. Also when it's shuddering, an odd noise is present somewhere at the front left of the engine bay (from the drivers seat)

It does it in all gear positions EXCEPT 1 & reverse.

I know it's probably nearing the end of it's usable life span-but aside from this it goes through all the gears just fine. Is there anything I can do short of removing it to aid or ideally fix this? Also, why doesn't it do it in 1?

Would it be totally pointless to replace the vacuum modulator?

Thanks guys!

Strictly internal if it is not a motor mount or axle you are feeling, no way to tell from here. BTW, excellent description of the problem, rare on these forums.