700R4 second gear noise

I have 6 month old stage-3 (650HP) professionally build 700R4 transmission sitting behind 454 in 68 Camaro RS. There appears to be a "wobble" noise when the car is in 2nd gear. Nothing like a grinding or knocking type of noise but rather a “waba-waba-waba…” type of noise. Almost like an exhaust/engine-load kind of noise even though my collectors/exhaust couplings are good and tight. I am 99% sure the noise is coming from the transmission. Specifically the front of the transmission. The noise starts after shifting into 2nd and stops after the car gets into 3rd. Same thing when downshifting from 3rd to 2nd, the noise starts and stops when downshifting from 2nd to 1st. As far as I can tell the transmission is shifting just fine or as advertised. Hard shift from 1st to 2nd (due to the shift kit) and a solid shift from 2nd to 3rd and 3rd to 4th, no slippage or any other visible issues. The only other thing I can mention is that when shifting the transmission into 1st or drive, the car will jump/lunge forward and you have to hit the break to keep it from going forward. I've contacted the transmission manufacturer about the jump/lunge issue and was told that is normal and expected as these are the hard 1st gear clutches engaging that they put in. Personally I thought it may be a bad torque converter which they supplied as part of the package. I was told not to worry about the transmission not being able to handle this jump/lunge but rather make sure my driveshaft is beefy enough to handle this (and it is). I am still hoping that my 2nd gear noise is somehow related to the torque converter but I am not sure how to diagnose this or perhaps a whole different problem. I have not mentioned the 2nd gear noise to the manufacturer yet as I am trying to diagnose it myself first. Any feedback would be greatly appreciated. Thanks in advance, Matt.