Yes, The growling works on Greys all times of the year.
I've never figured out whether Greys are unusually curious, suicidal, territorial, stupid, wanting to watch a good fight or if they just suffer small dog syndrom.
The only adverse reaction you would have is getting the young ones in real close. By thatI mean under 30-40 yards. Greys will inveribly jump to the high rocks to take a look-see and then scurry on in. That is of course if they aren't watching you walk around. Even then they will hang around.
The calls are Coon Squallers or Growlers. They have a reed between two tone boards. Don't let the name on the box fool you with the words "Fox Call". These are merely predator calls like all others with the metal reed inside. They call fox too but aren't the aggressive sounds of a fox fight. Make sure it has the two protruding tone boards.
Johnny Stewart (plastic) made a real good Coon Squaller in years past and can still be found today because for the most part, nobody knows how to use them and they also think it is too aggresive of a sound to bring a tiny little fox in.
Lohman (wood) also made an excellant Coon Growler. Same thing goes for it as does the JS.
Other old-timey calls would be Elto, Jake Frye and Son, Blow-Dri, Ol' Jake's and Sta-Dri.
Will they work on Reds? I dunno. I would imagine they would but honestly, I have no experience with Reds.
When I use that sound to call greys, I don't mix the sound with stereotypical jacks, cottontails or distress. If anything I will throw in puppy yelps.
If you listen to JS Tapes with greys, it makes a helluva racket. Get you one of those tapes and sing along for a minute or two and when your wife starts hollerin', you'll know you're ready to Go Fer Greys.