I am just about ready to order a F150 Screw 2x4 KR, approximately 10% of mileage will be towing 4500 lbs. Live in SoCal - rarely see snow, some rain. Which differential is better in what conditions?

 

My personal opinion is limited slip is best in all conditions. If you tow a boat and get on slippery ramps, get the limited slip. Wet roads, limited slip is better.
I had one F150 with an open rear end. Never again. If buying off the lot, an open rear end would be a no sale for me.

 

If you are going 2x4 I would go LS. It really doesn't change the driveablity much at all and it might save you sometime when that one wheel is spining in the mud and the other is sitting on the dry asphalt.

 

I wouldn't order a truck without a LS.

 

LS. It's not even noticable under normal driving conditions. You won't even know it's there until you need it. I have an open axle on this truck and I spun my tires driving across a wet grass front lawn. I'm getting ready to regear and I am not going to go through all that hassle without also putting in LS clutch packs. If you are unfortunate to live where you see snow then an open rear should not even be an option.

 

It's just not a truck without a limited slip diff. Just be aware that if your on a slick surface, the rear will tend to slide out if you get on the throttle with a LS.

Nothing to be worried about, perfectly normal, just be aware of it.

 

LS. for sure, my buddy has a 99 F150 with the 5.4 and a non LS. rear, if you need to get out on the highway on a rainy day, forget it.....the right wheel just spins off and sits there going nowhere. For the extra 300$ or so that it costs, its worth every penny.

 

I never understood why Ford doesn't gouge a lot more for that option.

$300 is a bargain.
It would have to be in the four figure range before I would say no.

 

I bought a used '99 with the towing option, and the dam thing had an open rear end! Made no sense!

Anyway, as said above, you get real familiar with the sound of one wheel spinning. On any surface.

So, I bought an Auburn Gear LS unit and had it installed. It appears to be an easy job, but a wrench buddy of mine said the endplay adjustments are a) critical and b) involve some sort of voodoo.

$500, and now both back tires spin! But only when I want them to

So, the long answer to a short question: Get the LS option!

 

I agree. I would never buy a new truck without a limited slip rear whether or not it was a 4x4.
I had a used94F1504x4 before I bought my 2000F150Scab4x4 with traction lock rear and the traction in the snow is much better with the 2000.

If I bought a used truck that did not have one, I would install a limited slip or a locker like Power trax.

I have had 2 wheel drive trucks in the past without LS and flooring the gas on a wet road at 55mph would produce right rear wheel spin! NOT COOL!