EXHIBIT 5.1

          [Letterhead of Fried, Frank, Harris, Shriver & Jacobson
            (a partnership including professional corporations)]

May 25, 2001

SPX Corporation
700 Terrace Point Drive
Muskegon, Michigan  49443-3301

RE:  Registration Statement on Form S-8

Ladies and Gentlemen:

SPX Corporation (the "Company") is filing with the Securities and Exchange
Commission a registration statement on Form S-8 (the "Registration
Statement") with respect to an aggregate of 544,945 shares of common stock,
par value $0.01 per share, of the Company (the "Shares") for issuance (1)
upon the exercise of certain stock options, and (2) under the United
Dominion Industries, Inc. Compass Plan and the United Dominion Industries,
Inc. Compass Plan for Hourly Employees (the "401(k) Plans"). Upon the
consummation of the amalgamation under the Merger Agreement (the "Merger
Agreement"), dated as of March 10, 2001, by and between the Company and
United Dominion Industries Limited ("UDI"), stock options previously
granted by UDI under (i) the United Dominion Industries Limited 1999 Stock
Option and Restricted Stock Plan, (ii) the United Dominion Industries
Limited Stock Option and Restricted Stock Plan and (iii) the Stock Option
Plan for Key Employees, Officers and Directors of United Dominion
Industries Limited (the "Option Plans") were automatically exchanged for
options to purchase Shares. In addition, following the consummation of the
amalgamation, Shares will become an investment alternative under the 401(k)
Plans.

With your permission, all assumptions and statements of reliance herein
have been made without any independent investigation or verification on our
part except to the extent otherwise expressly stated, and we express no
opinion with respect to the subject matter or accuracy of such assumptions
or items relied upon.

In connection with this opinion, we have (i) investigated such questions of
law, (ii) examined originals or certified, conformed or reproduction copies
of such agreements, instruments, documents and records of the Company, such
certificates of public officials and such other documents and (iii)
received such information from officers and representatives of the Company
and others, in each case as we have deemed necessary or appropriate for the
purposes of this opinion. In all such examinations, we have assumed the
legal capacity of all natural persons, the genuineness of all signatures,
the authenticity of original and certified documents and the conformity to
original or certified copies of all copies submitted to us as conformed or
reproduction copies. As to various questions of fact relevant to the
opinion expressed herein, we have relied upon, and assume the accuracy of,
representations and warranties contained in documents and certificates and
oral or written statements and other information of or from public
officials, officers or representatives of the Company and others, and
assume compliance on the part of all parties to the documents, with the
covenants and agreements contained therein. We also have assumed that any
future changes to the terms and conditions of the Option Plans and the
401(k) Plans will be duly authorized by the Company and will comply with
all applicable laws.

Based upon and subject to the foregoing, we are of the opinion that the
Shares have been duly authorized and reserved, and, when issued and paid
for (with the consideration received by the Company being not less than the
par value thereof) in accordance with (1) the provisions of the Option
Plans and the applicable option agreements thereunder or (2) the provisions
of the 401(k) Plans, as applicable, will be validly issued, fully paid and
non-assessable.

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

The opinion expressed herein is limited to the General Corporation Law of
the State of Delaware ("DGCL") and applicable provisions of the Delaware
Constitution, in each case as currently in effect, and reported judicial
decisions interpreting the DGCL and the Delaware Constitution.

Very truly yours,

FRIED, FRANK, HARRIS, SHRIVER & JACOBSON


By: /s/ Aviva Diamant
   -------------------------------------
              Aviva Diamant