1
                                                                     Exhibit 5.1

                           Gardner, Carton & Douglas
                       321 North Clark Street, Suite 3400
                            Chicago, Illinois 60610


                                October 22, 1997


SPX Corporation
700 Terrace Point Drive
Muskegon, Michigan  49443

         Re:     Registration Statement on Form S-8

Ladies and Gentlemen:

         We have acted as counsel to SPX Corporation, a Delaware corporation
(the "Corporation"), in connection with the filing of a Registration Statement
on Form S-8 by the Corporation under the Securities Act of 1933, as amended
(the "Registration Statement"), which Registration Statement registers 50,000
shares of Common Stock of the Corporation, par value $10 per share (the "Common
Stock"), reserved for issuance under the SPX Corporation Employee Stock
Purchase Plan (the "Plan").  In that capacity, we have reviewed the Certificate
of Incorporation and By-laws of the Corporation, both as amended to date, the
Registration Statement, the Plan, the originals or copies of corporate records
reflecting the corporate action taken by the Corporation in connection with the
approval of the Plan and the issuance of the Common Stock under the Plan and
such other instruments as we have deemed necessary for the issuance of this
opinion.

         Based upon the foregoing, we are of the opinion that the Common Stock
to be offered under the Plan has been duly authorized by all requisite action
on the part of the Corporation and, when issued in accordance with the terms
and conditions of the Plan, will be legally issued, fully paid and
non-assessable.

         We consent to the filing of this opinion as an exhibit to the
Registration Statement.  In giving this consent, we do not admit that we are
within the category of persons whose consent is required by Section 7 of the
Securities Act of 1933, as amended.

                                        Very truly yours,

                                        GARDNER, CARTON & DOUGLAS