I have a 1999 Mercury  Mountaineer. I have a Dana 35. I have been told this is not your normal Dana 35. I have been told I cannot use the normal aftermarket diffs and lockers. Has anybody had any luck with mods or getting limited slip, or a unlockable locker in one of these?

I have been told that I would have to grind grooves in the lockers that are normally for the Dana 35, and also that my Front diff case may be narrower then the normal Dana 35, so I would have to turn something down, to get the bearing spacing correct.

I don't want a full time locker, because I drive on the snow and ice on the roads alot, and I don't want to get pushed through a corner. I have talked to Powertrax, Eaton, OX, and ARB manufacturers, and they say they don't have anything for me.

Of course if you look in the Powertrax application guide, it says the 2311 locker would work, but I others say it won't. I don't really want to have to let completely off the gas, until I get around the corner everytime.

Anyways, my Dana ID code is 610642-2.  It is a Dana 35, but from the outside, because of the cover, it looks exactly like a Dana 30 by all the pictures I have looked at, but according to the Ford number which is D041A, it crosses to the 610642-2, which is a Dana 35.

The part number also lists it as a 1998 to 1998 1/2. But mine is a 1999, so it must be a early 1999. My door says it was built in October of 1998 I believe, so I guess that's why it has a 1998 front diff in.

610642 Ford 35 Front 1998-98 1/2 Explorer - Non-disconnect (sla Ifs)

Anyways, I am looking to get some type of limited slip, or unlockable locker in the front, either electrically, or pneumatic ran, so I can turn it off when I am on the street, in the ice and snow.  

True a True Trax gear based LSD diff up front. They play really well up there. Military Hummers have been using them since day one front and rear and OshKosh plows truck which are legendary for their performance in snow have been using a version of this design for well version 30 years now.  

yeah..the true trax is a awesome unit..
generally in the ice and snow a locker'll cause more trouble than it's worth..depending on your driving skill.