There are no records for your ggrandfather nor is there a roster or history of Gunter's Battalion but a few bits and pieces.

Gunter's AR Cavalry Battalion, (3rd Battalion) also called Woosley's Battalion
Organized: on 4/20/64 Mustered Out: 5/26/65
Thomas M. Gunter, Lieut. Colonel
James Woosley, Major

From April 64' to August 64' they served in Cabell's Brigade, Fagan's Cavalry in the District of Arkansas, Trans-Mississippi Dept.

From August 64' through May 65' they served with the 1st Arkansas Cavalry, Price's Corps., Trans-Mississippi Dept.

...

Gunter's Cavalry Battalion was assembled during the fall of 1863 and served under General Cabell in the Trans-Mississippi Department. It took an active part in the conflicts at Elkins' Ferry and Marks’ Mills, then participated in Price's Missouri Expedition. After some light action, the unit disbanded prior to the surrender in June, 1865. Commanders were Lieutenant Colonel Thomas M. Gunter and Major James Woosley.

...

12/17/63 Gunter to command of a cavalry battalion-
From Bryan Howerton’s post Date: Wednesday, 3 October 2001, at 10:42 a.m
…Regarding Gunter's battalion -- Thomas Montague Gunter was a lieutenant-colonel in the 34th (Brooks') Arkansas Infantry when he was given command of a battalion of cavalry on December 17, 1863. Gunter's battalion is sometimes referred to as the 3rd Battalion Arkansas Cavalry. No muster rolls of the battalion, or service records of the men, can be found. Gunter's battalion served in Maj. Gen. James F. Fagan's division in the Camden Expedition and Price's Missouri Campaign
http://history-sites.com/cgi-bin/bbs62x/arcwmb/webbbs_config.pl?md=read;id=25380

See also:

http://history-sites.com/cgi-bin/bbs62x/arcwmb/webbbs_config.pl?md=read;id=25370

http://search.yahoo.com/search?p=Gunter%27s+Arkansas+Cavalry+Battalion&ei=UTF-8&fr=clearspringsf