2001 Montero Sport LTD, when I put it into drive it doesn't engage, like its in neutral the engine revs but nothing. If I go into third drive a little bit and then shift into drive its fine. Doesn't happen all of the time and doesn't seem to be a pattern to it. Occasionally it will also slip out of drive into neutral, but that's only happened a couple times. Other than that it shifts fine.

Any idea's?

 

Check your transmission fluid levels and check it for dirt and metal bits if it's still full.
A flush and refill might help too.

If all that checks out you may be on your way to transmission rebuild-sville population you.

 

IF you have to rebuild, let me give you some advice. My 2002 Montero Limited was in and out of commission most of this year trying to get the trans rebuilt. The transmission is complex and rebuilds are rare so most shops cannot get it right. Even the dealers will tell you to replace.
We finally gave up and sourced a 67K used transmission and it works flawlessly. I would have saved about $2K and months if I had done that in the first place.
Unless you have a shop that KNOWS the Mitsubishi transmissions cold, save yourself some trouble and just replace.

 

I was afraid of that. Thanks for the advice. I've seen used transmissions on Craigslist for around $350.00. I've already changed the fluid with no difference. So at this point I'll run it until it won't go anymore and then go the replacement route.