So after doing some searching I have came across some info for what I have been searching but it seems mixed. My Montero does not have LSD. So From what I understand I could swap out for the LSD Rear from same year. I also understand the Arb makes an aftermarket. Otherwise I seen bits and pieces of info hinting that a 99 or older SR model would bolt on the 2001. Is there any truth to this?

 

ARB makes an Air-Locker differential. That is actual locking dif, not just a limited slip. It is a great option for off-roading, but it cost a pretty penny. Plus you'll need to have an air compressor installed to run it.
Sorry can't help with the diff swap question - no experience in that area.

 

not entirely true. a small air tank will switch a diff many times and only needs to be charged up when at home.
alternately, it's fairly common to adapt an air conditioning compressor to an air compressor for on-tap PSIs.


to the OP.
what is your intent? 2001 is a car. 4x2 is a car, why the hell would you bother paying for a slip diff in it?

 

That is not a bad idea. I suppose you can even use one of those tire re-inflating type of cylinders that can be screwed onto a tire valve (not the tire seal filler stuff, just air tank). I do hope the OP has a 4x4 Montero, not a 4x2 Do they even make 4x2 Monteros?

 

Nope its a 4x2 :/

 

Sorry about that. You just going to have to stay on the paved roads . There is no point to do much to your differential - it's not going to improve much.

 

This is FACT !!!!

 

I have successfully swapped the factory air locker from a 95 Montero SR into my 2002 montero sport xls (2wd, non-abs, 3.5L). You have to make sure the the gear ratios match. I believe the 3.0l MS is 4.93 and the 3.5l MS is 4.63 (same as the SR). One added benefit with the swap is that the rear brakes change from from to disc. I think if you have a abs then you may run into issues with the abs sensor ring tooth count and/or spacing on the hub.

 

Sounds like you swapped the entire back axle?

 

Yes almost... I don't have the complete list off the top of my head but when I pulled the parts from the SR at the U-pull it salvage I took the entire rear axle assembly (both half shafts including brake components, the third member and brake plumbing) the dash switch, air compressor and some wiring. I knew ahead of time that neither the spring mounts nor trailing arms are in the same position on the sport as the SR but I wanted to have everything from the rear axle just in case. When it was all said and done, I ended up purchasing new brake calipers and parking brake cables. The calipers from the yard were returned as cores. I'll have to go back and look but if there is interest I can try to find any pictures and or notes I have from the swap.