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                                                                  EXHIBIT (b)(4)


                     [ARKANSAS BEST CORPORATION LETTERHEAD]



                                 March 15, 1999


Members of the Special Committee
of the Board of Directors of Treadco, Inc.:
Mr. Nicolas M. Georgitsis,
Mr. Robert B. Gilbert

Stephens Inc.
111 Center Street, Suite 2400
Little Rock, Arkansas 72203

Attention: Noel M. Strauss

         Re:  Treadco, Inc.

Ladies and Gentlemen:

         In connection with negotiation of the proposed acquisition of Treadco,
Inc. ("Treadco") by Arkansas Best Corporation ("ABC"), the management of Treadco
(i) has provided Stephens Inc. ("Stephens") in its capacity as financial advisor
to the Special Committee of the Board of Directors of Treadco, certain internal
nonpublic financial information including the management projections of Treadco
presented to the Board of Directors of Treadco on December 9, 1998 (the
"Management Projections") and (ii) provided input to Stephens in its preparation
of revised projections for Treadco (the "Revised Projections"). Management of
Treadco has also provided to ABC and Stephens the preliminary results of
operations of Treadco for the two months ended February 28, 1999 (the "YTD
Results").

         The Management Projections and the Revised Projections have been
furnished to and reviewed by ABC, and ABC has participated in discussions with
the management of Treadco and Stephens regarding the methodology and basis for
such projections, including inquiries of the management of Treadco it deemed
necessary or appropriate.

         Based on such review and inquiry as well as a review of the YTD
Results, ABC advises you that as of the date hereof and to the knowledge of ABC:
(i) the projected results of operations for the five year period ended December
31, 2003, taken as a whole, included in the Management Projections are not
significantly understated and (ii) there is no fact, circumstance, occurrence or
event not disclosed to Stephens in their preparation of the Revised Projections
that ABC believes would significantly impact Treadco's operating results for the
year ending December 31, 1999.

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Stephens Inc.
March 15, 1999
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         For the purposes hereof, "knowledge of ABC" shall mean the actual
knowledge of its executive officers and its officers or employees who are
officers or directors of Treadco.

         Actual results of Treadco could differ significantly from current
expectations due to a number of factors, including general economic conditions;
competitive initiatives and pricing pressures; labor relations; costs of raw
material; availability and cost of capital; shifts in market demand; weather
conditions; the performance and needs of industries served by Treadco's
businesses; actual future costs of operating expenses; self-insurance claims and
employee wages and benefits; actual costs of continuing investments in
technology; and the timing and amount of capital expenditures.


                                  Sincerely,

                                  ARKANSAS BEST CORPORATION


                                  By: /s/ DAVID E. LOEFFLER
                                     ---------------------------------------
                                     David E. Loeffler
                                     Vice President and Chief Financial Officer


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