92 cherokee wont start

i have a 92 cherokee. 4.0 ho. has about 152,000 miles. no problems until about a month ago.. when turn the key wont start. i noticed the rear back up lights no longer came on. so i figure the nss is going bad. havent had time to get new one or clean yet.. truck wont start in park.. no fire, nothing. when i put in neutral no problem. fires right up. until this morning. i get same thing in neutral now. no fire. whats the first thing i should probably check or replace? could the nss going bad also cause the truck to not start in neutral. or is this an additional problem to the nss going bad also

With it not starting in neutral or park and the back up lights not working either then all signs point to the NSS. If you have a 4 speed tranny then you can take it apart clean it out with carb or brake cleaner, sand down the copper contacts with a fine grade sand paper and then lube it back up with white lithium grease and reinstall it and that will hopefully take care of the problem. If you have the 3 speed tranny then not sure if it can be cleaned but the NSS is only about $20 at the auto parts stores. One tip if it is the 4 speed the trick to getting the NSS off is take the nut all the way off then put it back on a couple of turns and use a flat head screwdriver under the nut and against the tranny pan to pry it off and make sure that you clean up the bar that is sticking out of the tranny that it slides on to ease reinstallation too. If after cleaning it it still won't start then it could be the ignition switch on the lower part of the steering column under the dash causing problems too. But I'd try cleaning and rebuilding the NSS first as it's the cheapest and easiest and most problematic part.

What Dave said! Based on your symptoms, I'd agree it's the NSS.

http://jeepin.com/features/nss/index.asp

yep. i had to call off work to get the time to actually do this. work 16 hrs a day bout 6 days a week. but followed instructions. truck runs great. thx for the input.