My '89 is an ext. cab 2WD longbox, 5.8L/C6, 3.55 rear. When the road is wet, this truck gets no traction. I can feather the throttle and the rear tires will just sit and spin like I'm on ice. I have brand new tires on it, no difference.
I'm going to end up driving this truck through the winter (it's first time in salt) this year. Any ideas how I can get better traction? I've tried 300lb of weight with no difference. I don't wanna load it up too much and kill my 12mpg I get now.

 

Suspecting you might have some brakes stuck on in the front. Try jacking it up and check if they roll ok.

 

Open differential? The longer the bed, the farther away the rear end is from the weight of the engine and cab. You have less weight on the rear tires when compared to a short bed truck.

 

I also have long bed with 302 and 3.55LS; when I first bought it, I had a little problem with tire spin in initial rain, but after getting new tires in back, it went away. But if you just check your spin and they are ok, then it's simple physics. Any excessive rpm's or surge or anything else?

 

you may just need another 5 bags of sand (might come in handy this winter) in the bed, back near the tailgate - will usually solve this

 

Yep to all of the above. As a habit I try to keep my rear tank as full as possible. It's not as necessary now that I have a limited slip in the rear.

 

Brakes good, no hangups. It is a one leg rear, and I do have a Trac-Loc unit out of an Explorer that'll get installed. I'm hoping the softer snow tires will get better traction than the Wranglers on the truck now.

 

I had problems with Wranglers also hard rubber changed and problem went away.

 

Which limited slip did you put in?

 

Factory. Purchased an entire rear axle from a parts truck that had the same gearing and the factory traction lock limited slip.