As long as you support the torque wrench end of the extension and don't let it get into a bind, the torque shouldn't be affected. The only thing that would affect torque readings would be an adapter that offsets the torque wrench head away from being directly above the bolt or nut being tightened, like a "crowfoot" wrench. We used to use an offset wrench to retorque the Chevy small block V8 cylinder head bolts under the exhaust manifolds after warmup without having to remove the manifolds. Those required doing some math to get the torque right.
Jerry



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