I have a 1990 F150 2wd with the 5.0 motor, automatic transmission and an open differential. The truck has approx. 137,000 miles and was owned by my father in law. It gets driven very little, but is used for errands, hauling trash to the landfill, etc. We do get snowy roads in the winter here. I am considering adding a limited slip differential, and am debating on which one would be best. The Ford Trac Lock seems to be the least expensive, but I have read that it is not as effective as some. Auburn's is not too expensive, as well as some other clutch types. I don't want to spend too much, but would like to make it worthwhile. Does anyone have any suggestions?
Thanks

 

I personally like the Ford LS because it is has a serviceable clutch pack and is easy to rebuild. Make sure you get one that is 31 spline for trucks. I got one from a 5.0 Explorer along with the 3.73 gears.

 

I personally think that any clutch-type limited slip is a bad choice for winter driving. Even coasting around a corner the tire traction needs to overcome the friction in the diff. If there's not enough traction for that the tires will slide and the truck will start to swap ends. I know others disagree with me on this, but in my opinion an open diff (with the problem of maybe not being able to get started) is better in snow than a clutch-type limited slip (with the problem of maybe spinning out when coasting around a corner).

My personal first choice for winter driving is an automatic locker (like a Detroit, or one of the "lunch-box" lockers). They aren't for everyone though (i wouldn't want one in a vehicle my wife or older son would be driving). If you aren't careful enough with the throttle they can swap ends on you (any limited slip is worse than an open diff for this, but an automatic locker is worse than most limited slips). But if you are careful enough with the throttle I've found automatic lockers are very streetable (and won't make it more likely to swap ends while coasting). I also don't recommend an automatic locker if heavy towing is a big part of the truck's expected use. But other than that, if you are willing to learn to drive it like it needs to be driven, I'm a huge fan of an automatic locker in the rear axle.

This is my first winter with a TrueTrac gear-type limited slip. That would be my first choice for a vehicle that's expected to do heavy towing, or to be driven by people who don't want to (or aren't able to) adapt to the light foot required by an automatic locker. It's not as effective as a locker (or a tight clutch-type limited slip). And although anything other than an open diff will be more likely to spin you out if you get on the gas too much, the TrueTrac is more forgiving than an automatic locker (it doesn't require as light a foot) or a clutch-type limited slip (it won't spin you out while coasting).

A selectable locker is another option. They tend to be the most expensive, but they give you the stability of an open diff (which is definitely better than any other option) most of the time. And you can lock it when you need it. I wouldn't suggest locking it for general winter driving, so it would mean needing to lock and unlock it as the need arises, and personally i wouldn't want to deal with that for winter driving. But it is an option.

 

With snow being the concern i don't think a ls is going to do much for you. I owned a 2wd a long time ago and swapped in a ls rearend from another truck and it did help on backroads hunting with loose rock etc but snow was similar as to without ls.

 

I have a loc rite automatic locker in my rear end and when on normal flat roads it acts the same as an open rear end. The only time I had an issue was when the road had a side ways pitch to it and was covered in slushy snow. The rear end wanted to go down to the bottom of the pitch which in my case was the fast lane of the freeway.

now that i know that, when ever i drive on slick roads and they pitch upwards like that i make sure to be in the lane at the low end of the pitch but most of the time the roads are in decent shape so its not a problem. It is nice having the extra help from the other wheel in slippery situations.

 

Rear wheel drive vehicles just don't go good in the snow.Compound the issue by making one a truck and now you've got a bad/bad situation.A system made to push and a light one on top of it.The best way to fix the issue is to add a front axle and make the poor traction design pull,not only instead but in addition to push.
With the F150's it's actually just all bolt in but since it's not something used often,the best thing you can do is to add weight in the bed.Set a yard of dirt right over the rear axle in the bed.This will aid much more traction in snow more than adding a LS in the rear.Your still left with pushing a light box.Adding weight is near free and fast.Very effective too.It can make your truck go so much better,it will feel like your driving something far different.
Make sure you're running small/skinny tires too.Another good option really,especially if your 2wd is nice and clean as a result of it's poor traction,it probably spent most of it's life off winter roads.A little beater front wheel drive car for winter use is pretty hard to beat.

 

... and make sure those skinny tires are good snow tires. Studded tires (if allowed in your state, they aren't in mine) are best. Actual dedicated snow tires (like Blizzak) are next best. But good all-season radials, or a lot of all-terrain radials, are pretty good too (I like BFG A/Ts). Highway tires are not good and mud tires are terrible.

But yes, good tires and some weight in the bed will help a lot more than any differential will.

 

I like the factory LS diff when it is tightened up a bit and it will help with winter traction after your driving habits are adjusted a little bit to expect the rear end to slide around more, but with a 2wd reg cab 1/2 ton truck there are 2 things that are not optional IMO.. real winter tires and weight in the bed. With the heavier HD and extended and crew cabs trucks you can get away without weight and winter tires in some cases because there is more weight over the rear axle, and if you have 4wd that can be used when the roads are really slippery, but the 2wd reg cab has none of those things and is pretty much the worst possible vehicle for winter traction.

 

I wouldn't recommend getting a factory limited slip they aren't that good, if you have an open differential the cheapest option is getting a drop in locker like a Spartan, Aussie, or Lock Right, they replace your spider gears so you don't have to reset your backlash like you would if you change carriers. I daily drive with a locker in the rear and I would never go back to an open differential, the extra traction it gives you is great, the only time I notice it is when making slow turns in a parking lot the truck will jerk around a bit, you eventually learn how to put it in neutral and let it coast so it doesn't do that. That is with a manual transmission though, since you have an automatic it will be even less noticeable, I have one in the rear of my automatic Jeep and it doesn't do that at all, I let other people drive the Jeep and they don't even notice it has lockers. No problems towing with a auto locker either I tow all the time with my F250 with a Detroit locker and it does fine. However if you are dead set on a limited slip a Detroit Truetrac is the best option.

 

Is this what you mean by "Lunchbox Locker"? I have dealt with these a few times and never will again. Had one in a 9 inch rear in a 70 Mustang, and in two different F150s with 8.8. Maybe it works better in the HD rear axles. They are noisy, rough, jerky, etc and only work kinda smoothly for a few thousand miles. I did like the idea of how they work, but in the real world hate them except in mud.. I can't remember what brands they were, but I know one was an EZ locker, and it was terrible. The problem was going around normal street corners (it became so loud that it sounded like these vehicles were broken), not so much of an issue in parking lots.

 

I always thought the best thing might be an electric locker that was open for normal street use and then locked by a switch.

 

Yes that's it, I have three of them and don't have any of the issues you described. The EZ locker you referred to was Eaton's brand of this design, it was very problematic and is no longer made, the other brands I mentioned above are much better, I prefer the Spartan locker the most because of the internal spring and pin design.

 

Yep, that's one. I'm not sure which, but they all seem to look pretty much the same.

I had a Lock Right in the rear of a '95 F-150 SCSB with an automatic. As 00t444e said, the auto smooths them out quite a bit, but I certainly never noticed anything particularly harsh about the Lock Right. I've also had Detroits (auto locker, but not lunch-box) in the rear of a CJ5 and my '71 Bronco. Those are harsher than the F-150 was, but they were/are both manuals and shorter wheelbase, which accounts for that. In my experience there's no real difference in use between a Lock Right and a Detroit.

But as I said above, auto lockers aren't for everyone. If you don't value the performance and aren't willing to drive them easier on the road you probably won't like them.

 

That might explain why the one I had was the worst diff I've ever driven with.

 

The vehicles I had them in were automatic transmission and were just not driveable on the street. The mentioning of how problematic the Eaton EZ locker was may explain why one I had was so awful though.