Declare @Tbl Table (ID int, NAME varchar(50))
Insert Into @Tbl
Select 1001, 'CG14*13.5-85/31-37/113*23W'
Union All Select 1002, 'CG6.5*5.4-190/31-37/248*33W'
Union All Select 1003, 'CG5*5-105/30-32/103.5*10.5V+W'
Union All Select 1004, 'CG5*5-105/30-33/103*10.5'
Union All Select 1005, 'CG6.5*5.3-125/31-37/104*9.8B(V+W)'
Union All Select 1006, 'CG6.5*5.4-190/31-37/114.5*23P'

;With Tbl(ID, Num1, Num2)
As(
  Select ID, CAST(SUBSTRING(SUBSTRING(NAME, CHARINDEX('/', NAME) + 1, 5), 1, 2) As Int)
           , CAST(SUBSTRING(SUBSTRING(NAME, CHARINDEX('/', NAME) + 1, 5), 4, 2) As Int) 
  From @Tbl
) 
Update A Set A.Name = A.Name + Case When ABS(B.Num1-B.Num2) > 5 Then '/二' Else '/三' End
From @Tbl A Inner Join Tbl B On A.ID = B.ID

Select * From @Tbl

/*
ID          NAME
----------- --------------------------------------------------
1001        CG14*13.5-85/31-37/113*23W/二
1002        CG6.5*5.4-190/31-37/248*33W/二
1003        CG5*5-105/30-32/103.5*10.5V+W/三
1004        CG5*5-105/30-33/103*10.5/三
1005        CG6.5*5.3-125/31-37/104*9.8B(V+W)/二
1006        CG6.5*5.4-190/31-37/114.5*23P/二

*/