1Ton-K1500

Got a 97 k1500 with the above listed 4l60 and 241 case. Used 4lo the other day worked fine--went to use it yesterday and found it seems to slip in second gear. tranny shifts holds and runs out properly in 2wd. 4hi seems to work fine. tranny got 80k miles on it and fluid looks and smells great. just changed the t-case fluid about 3000 miles ago after i put new front and rear seals on it. Did stall test on the tranny and seems to hold just fine. Never had a 241 apart before so my question is does the case have any clutch packs in it? (thought they were chain and direct drive) Also why would it slip in second and not first or third? any input would be great. Thanks. Need to be back on road this weekend to help friend move