Jerry,

Your GGGrandfather was just the kind of guy those early CSA cavalry commanders were looking for . That Mexican War/ Texas Ranger experience was absolutely invaluable when the Civil War came along. Those guys were worth their weight in gold as far as experience fighting and surviving in harsh conditions and keeping their horse in good shape ( key !) . As far as I'm concerned ( and I think the famous historian Ed Bearss, would agree, in fact I heard him say so at a meeting last year ) these guys like your GGGrandfather , were the true creme de la creme of Southern Cavalry . They didn't look too fancy , but they were "hell on horseback" when it came to fighting . You know the 11th Texas Cav actually fought with the 8th Texas Cav ( Terry's Texas Rangers ) for a period of time . The late Col . Simpson ( of Hill Junior College, Hillsborough, Tx) always said that the 11th Texas Cav was just as hard a bunch of fighters and riders as the 8th , they just weren't as famous.
Since your man has that Texas Ranger / Mexican War link, you ought to be able to find out even more about him . There's a bunch of stuff written about Capt Jack Hays and Ben and Henry McCulloch as Texas Rangers during the war with Mexico . Your GGGrandfather may be mentioned by them because there weren't all that many of them. I've got several books about the Rangers activities in the Mexican War. Let me know if you're interested in knowing more about this subject.
Sorry for rambling on , CAM