Check the input shaft end play and the main shaft end play as well as the shifter system.

The third-fouth gear synchro hub bridges the gap between the input shaft and the main shaft so if there is a change in spacing from a failing bearing retainer of a bad bearing it will affect one or the other and sometimes both.

Kevin

87 Turbo Intercooled Raider, roller cam, torsen rear diff, LSD front diff, lockup auto with modified converter, V6 brakes, low transfer case gears...