Between October 1957 and February 1958, the _TT_ vans remaining in freight service were recoded to BB. They were also renumbered and became numbers 1 - 21.
Some vans were fitted with cast bogies during 1960.
Ten vans were scrapped between 1959 and 1961.
To segregate wooden construction BB vans from steel type _BB_ vans, these wooden boxvans were recoded to _BA_ in 1961/1962. The vans were renumbered with the recoding. The BA number group was 1 - 12.
The renumbering was interesting. BB's 1 - 9 still in service were recoded to BA with no number change. BB's from 10 onwards were used to fill the BA number gaps. In the process, there was no BA 6. This made the group BA 1 - 5, 7 - 12. This is usually an indication that a list was prepared and followed for the renumbering. Between the list being drawn up and actual work carried out the vehicle that was to be No.6 was scrapped. From the data, this would be BB 15, scrapped 18/12/1961.
The only conversion from this BB type was BB 2 which was scrapped in 1960 and the underframe used for the vehicle _QD_ 2 construction in 1966.