The proton-rich isotopes 3ZAr-3SAr represent the first sequence for which the superallowed Gamow-Teller strength is known out to Z-N=4. The results are compared with two sets of predictions from large shell-model calculations, which give systematically different quenching factors, on the average 0.54 and 0.89. Possible reasons for this are discussed. A comparison is also made with the Gamow-Teller strength of proton-rich isotopes of neighbouring elements.