Saw this, Flex-a-lite fans:

Dual 15" S-blades move 6000 CFM!
Includes new Variable Speed Control (60% to 100% depending on cooling required)
Glass reinforced nylon injection molded shroud
Dyno tests showed a gain of 27HP & 34 lb-ft. torque at the wheels
Increase fuel mileage by at least 1 MPG
Cooler A/C output
Quicker engine warm-up
Size: 17" high x 31-7/8" wide x 4-1/2 deep

I do not recommend this product. Needs to be thought out better, and the HP numbers aren't backed up by dyno results IMO.

PS, it is not recommended for heavy towing.

i've got them and have had a few controllers fail. they have a new controller now that has the high current wires soldered to the controller vs. spade connectors like the old one. so far its working well. they also went from a maxi-fuse to a self-resetting breaker. if you race it works well, but if you tow i wouldn't get it. i couldn't tow my 8500lb boat from seal level to 8000' without stopping a few times to let the motor cool down.

the engine does warm up faster for sure which is nice, especially in the cold weather. it just depends if it suits you or not

They say good for 18,000 GVW. Not so, eh?
I have a 5,000 boat and 5,000 lb truck camper. I'd be at 17,500 gvw.
Was thinking this would be nice since today I drove my truck with the winter cover on when temps were in the 50s. The stock fan sucks a lot of power and makes a lot of noise.

They say good for 18,000 GVW. Not so, eh?
I have a 5,000 boat and 5,000 lb truck camper. I'd be at 17,500 gvw.
Was thinking this would be nice since today I drove my truck with the winter cover on when temps were in the 50s. The stock fan sucks a lot of power and makes a lot of noise.

By themselves they will not work well, your just wasting money. If you add other mods some electric fans will work well.... I have about 12000 miles on a set now and I am heading to San Diego in a few weeks pulling my fiver. That will add another 3000 miles to the test setup... IF they work well on this trip I will be 100% sold on electric fans...

what setup are you running?

Winter cover at 50 degrees? Good god man...And you wonder why you heard the fan running...

yeah i missed that...i had to take mine off with it got in the mid-high 30's...

Ive never used my winter front cover...

I Didn't At All Last Year...but I Got Sick Of It Taking Forever For My Truck To Heat Up...besides...those LiLLY's don't seem to have a problem heating up...us LB7 guys need all the help we can get

Someone who's got a little background in physics can figure this out easily; all you would need to do is compute the force required to spin a fan weighing x kilograms at a certain number of rpm's; you'd need the mass of the fan, rolling friction of the bearings, and the RPM of the engine. wind resistance would not factor in, because it would only REDUCE the amount of power required. i'm guessing that a fan weighing <10kg could NEVER require >20hp to rotate at 5000RPM max.

I have ran both my LBZ and LB7 with it being 50* outside and I dont have an issue with over heating or even the fan running much if at all. Sometimes happens when you get a warm spell in winter and I'm too lazy to remove the winter front. Trans runs cooler with the 06 with the cooler being relocated.....

If you run into it running hot with the winter front take it off or get a aftermarket one were you can pull just the top or bottom cover ;)

Hummm, That's odd. My truck is warm enough for the automatic heater control to allow warm air to the cab in about 3 miles from start-up. Until then the butt-warmer seats keep me warm and toasty. I stopped trying to out-do the factory engineers when I outgrew my young and dumb stage. My wallet is still thanking me.

I stopped trying to out-do the factory engineers when I outgrew my young and dumb stage. My wallet is still thanking me.

I have the same philosophy about many mods that seem pretty common; at least things that don't seem like there would be any reason for GM to NOT include them on the trucks... I have serious doubt of many things which replace factory equipment; I think for the most part GM engineers know what they're doing.