100K miles, quite possable. Usally the LB3 clutches go first (reverse). To do a quick test to guage wear. Move gear shift lever from R to P quickly and observe severity and delay of engagement. If delayed into D and then clunks, usally means B2 band/drum worn. If reverse delay/clunk, worn clutches (LB3), however you could replace the spring for accumulator 3-4 shift. If a different spring is installed, it may improve the flare. Also keep in mind 3-4 flare is K2 and K3 clutches being applied and damage may have already been done.
Mercedes-Benz Master Guild - 2 years
Shop Foreman - 20 + years - dealer.
Part owner - MBZ Transmission remanufacture