Transmission guys? 98 Jeep 4speed auto.Not locking up?

140 k,98 jeep sport. Bought it with 2 bad codes. -Bad voltage from torgue converter ($ lotta money). Bad master solinoid in the pan ($ 250 bux).- Looks electrical but works fine when cold. Bam bam bam shifts solid like a 4 speed auto. Taching 1700rpm @ 60 mph. Warmed up acting up 2000 rpm @ 50 mph. Fluid looks uused. Hasn't been hacked on (wiring). Shoot me some free advice or your thoughts.