But staff were visited by NZRU representatives who told them it needed to be altered or removed because it was in breach of trademark regulations.
A company spokesman said today they had reached a compromise with the union and changed the sign to read "Go the ABs" - at a significant cost, which he refused to reveal.
NZRU officials had taken issue with the use of the words 'All Blacks' but the spokesman believed it was also to protect Ford, an official sponsor of the event.
There was no animosity between the company and the union, and they understood the need to protect the All Blacks brand, said the Giltrap spokesman.
NZRU spokesman Nick Brown said it had a responsibility to those who paid to be associated with the All Blacks brand to protect it from those trying to make a quick buck from it.
"We have contacted businesses who are blatantly using the All Blacks brand to promote their products and businesses, but by and large, many are just wanting to show their support for the team," he said.
"We have discussed with a small number of businesses, how they can amend signs to keep the spirit of supporting the team, without encroaching on the rights of our sponsors."
Mr Brown said the union's focus was mainly on businesses trying to use the All Blacks brand for their own commercial gain.
"Otherwise, we are definitely encouraging them to show their colours and get behind the team during this wonderful tournament," he said.
Trademark lawyer Sheana Wheeldon said All Blacks was a registered trademark, so goods and services were prohibited from using the name and reputation of the team to make money.
The recent Major Events Management Act 2007 also banned people or companies from associating themselves with an event if they were not a sponsor, and there were additional regulations if they were on a main road, said Ms Wheeldon.
"I suspect that's what's happening (with Giltrap Audi). If it falsely creates an impression that they are linked to the All Blacks and are a sponsor then it could be misleading," she said.
"It certainly is cheeky and probably going to get a bit of advantage from the World Cup. Whether it crosses the line, I suspect it doesn't, but I can see why (organisers) don't have a sense of humour about it."
Officials were taking an "aggressive" approach to what they associated with the event, said Ms Wheeldon.
The International Rugby Board, Rugby New Zealand, Ministry of Economic Development and local councils across the country have been working together to stop non-sponsor brands getting free publicity through association with the event.
In March the Rugby Union and iwi Ngati Toa signed an agreement giving the All Blacks' the right to perform the haka Ka Mate.
No one has a registered trademark for the Ka Mate haka, which has become part of the Kiwi culture.
Ngati Toa filed an application to trademark four main phrases of the haka last year, after an earlier application to the rights to the entire text failed.
The NZRU then settled a deal with Ngati Toa ensuring it could continue to be performed respectfully by the All Blacks.
