Warren makes good stuff, under many different private labels, I wouldn't hesitate to use ANYTHING they make, whether it has an ST label, or Mag1, or any other name!
FWIW, drained the transaxle in my high hours John Deere 216 (vintage) lawn tractor and refilled it with ST 75-90 gear lube. Had a small leak before the drain/refill.
The 40 C vis of 347 seems a bit high for the conventional 75w140. For the Saskatchewan, Manitoba, and Montana boys, here is a comparison of 75W90 with 80w90. For entertainment only. Not planning on having a vis argument. Enjoy.