My employment contract contains a clause limiting any remedies for a personal grievance to my period of notice. Is this legal?

No, the Employment Contracts Act allows employers and employees to agree on an alternative procedure for settling personal grievances other than the procedure set out in the Act, but it does not allow them to provide for alternative remedies.

In fact, section 157 prohibits contracting out of the Act.

That is not to say of course that an employer and employee may not settle a personal grievance for remedy not provided for in the Act.

For example, an employer once settled a personal grievance at mediation by giving the employee six bottles of beer.

Another case settled by the employer giving the employee a car.