Poor's Manual of Railroads, by Henry Varnum Poor, Edition of 1881, details the early history of the railroad and its line which was eventually operated between Ann Arbor and South Lyon:

"In 1881, the company was called the Toledo and Ann Arbor Railroad Company, from Toledo to Ann Arbor, 46 miles.  It was completed on August 1, 1880.  The Toledo, Ann Arbor and North-eastern Railroad Company was organized to extend the former line 38 miles to Pontiac to reach the Grand Trunk Railway, and to bring that line into direct connection with the lines entering Toledo.

"At South Lyons [sic], on this extension, 15 miles north of Ann Arbor, and to which the line is now opened, a connection is now made with the Detroit, Lansing and Northern Railroad, with which a traffic contract for southern connections has been made.

"The rest of the extension is now ready for iron, which is being laid, to be completed to Pontiac by September 1, 1881."

A map from the Railroad Maps of the United States: A Selective Annotated Bibliography of Original 19th-century Maps in the Geography and Map Division of the Library of Congress, compiled by Andrew M. Modelski, Washington, Library of Congress, 1975, (below) shows the entire projected route of the Toledo, Ann Arbor and Grand Trunk Railway in 1881.  The latter portion, north of South Lyon, was never put into service by the TAA&GT and was soon sold to the Grand Trunk Railway which used it as part of its line to Jackson.

The segment of railroad from Ann Arbor to South Lyon remained in use until at least 11 August, 1890.  On that date, the Toledo, Ann Arbor and North Michigan

The original planned route from Toledo to Pontiac.  [RMLC]

Railway Co. (as the company was called after March, 1888) sold the 8 mile portion between Leland, north of Ann Arbor, and South Lyon, to the South Lyons [sic] and Northern Railway Company.  It is clear that Leland was the place where the newly consolidated line northwest to Frankfort diverged from the older line to South Lyon.  Modern maps don't indicate where the station known as Leland used to be, but it likely was situated south of Dhu Varren Road and west of Nixon Road.  In the 1892 edition of Poor's, the line to South Lyon is no longer shown. 

The map above is scanned from the 1901/1902 Survey Map of the Ann Arbor Quadrangle, produced by the Michigan State Board of Geological Survey.  The abandoned line is indicated in red.  Most modern day county roads can be found on this map, and used as a point of reference to locate the old grade.

Comment regarding the location of Leland, Michigan

References:

[MBGS] = Michigan State Board of Geological Survey, 1901-1902.

[RMLC] = Railroad Maps of the United States: A Selective Annotated Bibliography of Original 19th-century Maps in the Geography and Map Division of the Library of Congress.