I had dual Hayden e-fans on a 92 C1500 5.0TBI, worked great in terms of cooling, gained like 2MPG, but at idle the wimply stock alternator couldn't keep up and the battery would actually be discharging. After about a month the Hayden e-fan controller died on me (even though since I'd heard horror stories about them happening, I had separate relays for the fans so barely any load was on the controller) in traffic, on my day off, about a block from work, so I pulled into the parking lot, ripped the whole e-fan setup out, bolted the mechanical clutch fan setup back on, and got where I was going. Between that experience and the factory e-fan on my 99 Crown Vic going out on a really hot day and leaving me on the side of the road with two of my friends, I'll keep the stock clutch fan setup on my Suburban.