Did you drive it in high range just before you did the installation? Were there good instructions with the kit? Just trying to think this out. I dont have an reb kit on my M211.Possibly an automatic tranny expert could give you a suggestion? Can you take pictures of it?Are you sure the linkage isnt out of adjustment? I dont know what is involved in putting a kit on it. Just trying to help. I would have someone put shift in to the high range while you are underneath the truck, with it turned off of course and see what the linkage is doing. Thats my best guess. Something to do with the shifter linkage. Do you have the manual on the truck? The manual tells alot about adjustments, to linkages and says it could be a bad reduction unit/ Is the oil level just right? After refilling it says to put it in high range drive with brake on and idle for five minutes then recheck the dipstick.After doing this, it should take 4 more quarts , using approximately 16 quarts. It says to use the dipstick as your final determination of correct oil level. Not to go by the aprox. amount of quarts.At this time it should be filled to the cold full mark on the stick. Then idle truck until engine is up to full temp and trans up to temp. Recheck stick and adjust level to "full hot". I am no tranny expert, just quoting from the manual a few simple things to try in case you dont have the manual. Let me know how it works out.