Your Grandfather was assigned to Battery B, 133d Field Artillery Battalion which served as fire support for 1st Battalion, 143rd Infantry. Both B/133 and 1/143 were organic elements of 36th ("Texas") Infantry Division. His grade was Technician Fifth Grade (Tech5), a specialist rating of the Fifth Pay Grade, the same grade as the rank of corporal.
At this late date, your best - and probably only - possibility for contacting anyone who served with him would be the division's veterans' association. Their main page is