98 blazer 4x4 auto my 4wd was workingfine earlier today, tonite i was on an icy road when i selected 4hi nothing happened the lights went blank then after a ong delay 4hi lit up but it would not shift out of 4hi after i drve a mile i tried again but the 4hi 4lo indicatrs were flashing then it eventually shifted into 2hi now it wont go into 4hi at all any suggestions

 

Which 4wd system do you have? NV233 has the 3-button switch in the dash and the NV236 has the 4-button with auto4wd option.

With either, you should see if disconnecting the battery helps. If so, it likely is an encoder fault that was present.

If you have the NV233, before disconnecting the battery, check for codes stored in the TCCM by following the procedure found in THIS THREAD (which is located in the DIY section along with a LOT of other informative posts).

 

after i had posted my problem i kept searching and saw that another guy had a similar problem and solved his problem by disconnecting the battery. later that night i disconnected my battery and it cleared whatever problem there was. unfortunatly i assume i lost the codes that might have been stored. since i have your attention whenever i shift out of 4hi while driving i get a very loud thud when the 4wd disengages,,, any ideas