Over 200 workers, who maintain and repair rail stock, including carriages, wheels and bogies, have already taken nine days of strike action during June and early July.
They will move to all out strike on July 19, which will bring the site to a complete close.
The strike will shut down services for Wabtec clients including LNER, Siemens, Hitachi, GB Railfreight and Freightliner, with potential knock-on impacts on the availability of both passenger and freight rail stock.
Unions say the US-owned Wabtec is seeking to fire and rehire the workers onto new contracts that will see breaks cut and staff having to work extra hours, including at the end of their shift, for no extra pay.
They add the company is offering workers that sign the contracts a two-year below inflation pay rise.
Bosses at Unite and the RMT say staff are being pressured into signing the new contracts in one-to-one meetings with management. The unions are advising workers that they do not have to sign and can fight this attempt to force changes to their terms and conditions.
Unions bosses added that Wabtec’s total sales for 2021 were £6.43 billion, bringing in a record cash flow from operations of £880 million and it made dividend payments of £76 million.
Unite general secretary Sharon Graham said: “Wabtec’s abhorrent fire and rehire plans seek to make Doncaster’s workers worse off, working longer for less, for a company that has billions in the bank.
“Our members have no alternative but to shut this site down completely until the company steps back from these appalling and needless plans, which are a disgrace to Doncaster’s proud rail history.”
RMT general secretary Mick Lynch said: “Wabtec has behaved dreadfully from start to finish and now wants to fire staff and rehire them on inferior wages and conditions.
“This is totally unacceptable to RMT members who will now take all out strike action to reverse Wabtec’s despicable and arrogant behaviour.
“Wabtec bosses are bringing shame to Doncaster which has a proud history of manufacturing, with predecessors building the Flying Scotsman and Mallard locomotives.”
A spokesman for Wabtec, said: “We are disappointed with the Union’s rejection of our two-year 8.25 per cent wage increase proposal, which was not balloted by their members. We have spoken to employees directly which has resulted in more than 70 per cent of the workforce voluntarily agreeing to the new working practices and the pay increase.
Over the last 16 months, we have shared sobering facts with the Union on the need for flexibility and cost competitiveness and proposed a pathway to preserve work at the plant.
“The majority of our employees are clearly in support of this plan. In the end, Union leadership decided they would rather disregard the best interests of their members, and would not support Wabtec in building a strong future for the Doncaster workforce, where we have been a significant employer for over 170 years.”