Originally Posted by TrickyTransAm
Has no one changed their front diff fluid??
Use 75W90 or 80W90 gear oil in the front diff. It's no different than the 8.25" IFS under a 2012 for all intents and purposes.
Transfercase will take ATF.
Being it's an 88 it uses a thermal actuator and they are complete POS. Did you put in an electric one or another thermal style? You can get the newer style electric actuator and harness to replace it, or a Posi Lock cable system. Your choice. The thermals always were slow, right from day one. I guess make sure the collar moves freely in the front diff as well that connects and disconnects. Low on oil wouldn't help the situation at all.