any advantages/disadvantages. Not that I am gonna change. I have 3.73 LS in my 03 Exp. Just wondering what exactly do I have, good or bad?

 

it's a good thing.
basically an open differential works out to being 1 wheel drive because the wheel with the least traction gets all the power. in a limited slip diff there are a set of clutches that lock up giving power to both wheels when 1 slips.
the rear wheels need to be able to turn at different speeds when you turn a corner so that's why the can't be locked together at all times.
there are a few options when looking for a locking differential, but for most people the stock trac-loc(limited slip) is fine.
if you're interested in more you can google differential types and see all the options available.

 

thanks for a concise explanation. I was wondering about the idea to change gears for better mileage. Not sure which ratio would be best, and what the effects would be on power. Would it be correct to say that mpgs and power are sort of on a sea-saw? If one goes up, the other goes down?

I don't really tow anything, and the Ex has the tow package. Thinking the mpg gearing would be the priority.

What would ge a good ratio for mpgs?

 

I guess the 3.55 would improve highway mileage, but it might be too slow off the line. I believe my fx4 came with the 3.73 and while I wouldn't mind better highway mileage, I don't want it to be any slower off the line, so if I were to swap gears, I'd go taller rather than shorter.

I'm planning on going with a taller than stock tire once my current tires wear out, so I may go with a taller gear ratio to compensate, if the truck ends up being too much of a dog off the line. I'm already spending enough of my hard earned cash on gas though, so I'll cross that bridge when I get to it.
the thing that bugs me though is that my rear end seems to be an open diff. that doesn't make any sense at all to me on a 4x4 truck. I thought the fx4 came with a ls stock, but I can see my drivers side wheel standing still when my passenger side rear is spinning in snow.

 

An Expy is a pretty heavy beast. I think for gas mileage, the 3.73's you have now are pretty ideal.

 

The LS differential is an individual option and wasnt offered as part of any option package. And I agree it is dumb for the "FX4 Offroad Package" to not include a LS diff.

 

Is there an easy way to test the funktion of a LS differential? On paper i do have it, but with this winter´s performance i have a hared time believing it actually works propperly.

 

this thread got me very curious, so I did a bit of research and found a list of axle codes on this forum. turns out mine is a h9 which is suppose to be a 3.55 ls. it seems to work like an open diff to me?? I guess I'll have to get it spinning again and really hang my head out the door to be certain...

And finding out that I have 3.55 gears really makes me question whether or not I should up the tire size. I was gonna get 18" rims and tires when my current set wore out, but I'd probably need gears too and that may be more than I want to spend. Bad news. crappy gearing and a worn diff.

can a trac-loc wear out? it's a clutch type right?

 

H9, thats also what my sticker says. Hard to believe its ls. Let me know what you find out. And i think once your constantly marking the pavement with your tires you might get some play in the diff/clutches, but with normal use it should last as long as the rest of the vehicle.