The Ford Essex Engine plant is losing its midnight assembly shift starting October 1, 2019.
Members of Unifor Local 200 were informed of the reduction in jobs Wednesday night but there are no exact numbers yet.
Local President John D'Agnolo says the main reason is a shift in sales of the F-150 pickups.
He says smaller Ecoboost engines as well as a diesel option are moving buyers away from the 5-litre V8 they make at Essex.
D'Agnolo says they don't have final job impact yet because a new engine is about to start production.
"Because we have the new 7-litre program that's going into the Annex and a lot of the members that will lose their job on the midnight shift through openings will go to the Annex," says D'Agnolo.
He says the membership expected something like this.
"They weren't surprised, because we were seeing and having downshifts," says D'Agnolo. "Then we have two down weeks that are happening in July on top of our two week shutdown and then they have a two weeks scheduled in September."
He adds the V8 they make is also in the Mustang, but that's a much smaller number and isn't affecting the production at Essex engine.
There will still be three shifts running in pre-assembly areas like "crank, block and rod."