The SL-3 crew consisted of commander Alan L. Bean, science pilot Owen K. Garriott, and pilot Jack R. Lousma.
On 6 June, the SL-3 launch date had been changed from 8 August to 27 July; the launch date was subsequently changed to 28 July to optimize the rendezvous conditions. The prelaunch checkout was accelerated accordingly.
The S-IVB stage had arrived at KSC on 26 August 1971 and was placed in storage until 28 November 1972.
The CSM arrived on 1 December 1972 and was moved into the Operations and Checkout Building for systems testing. The S-IB stage arrived 30 March 1973 and was erected on Mobile Launcher 1 on 28 May.
The IU arrived at KSC 9 May. The S-IVB and IU were mated to the S IB 29 May. On 7 June the CSM/ spacecraft lunar module adapter was moved to the Vehicle Assembly Building and mated to the launch vehicle the following day.
SL-3 transfer to LC-39B was completed on 11 June. On 17 June, the mobile launcher and mobile service structure sustained several lightning strikes. The damaged parts for the CSM, mostly instrumentation, were replaced and retested or waived. The damaged ground support equipment parts were replaced and retested. The launch vehicle lightning retest revealed no related failures or effects on the launch vehicle or ground support equipment.
The flight readiness test was completed on 29 June. The final countdown began at 7:00 a.m. EDT 25 July in preparation for a 28 July launch (see 28 July entry).