Based on your original code and if you only ever have parts and labor then the below should work.

Not tested due to not having the DDL of the tables and sample data but the general idea is there for you to tweak.

DECLARE @StartDate DATETIME

DECLARE @EndDate DATETIME

SET @StartDate = '1/1/2012'

SET @EndDate = '1/31/2012'

SELECT B.EngEquipID

,B.Location

,B.Cycles

,B.DateTimeStamp

,'Labor' AS Labour

,CASE WHEN B.Source = 'Labor' THEN SUM(B.TRANS_tambase_amt) END as [Labor Total Amount]

,'Parts' AS Parts

,CASE WHEN B.Source = 'Parts' THEN SUM(B.TRANS_tambase_amt) END as [Parts Total Amount]

FROM (

SELECT ER.EngEquipID

,ER.Location

,ER.Cycles

,ER.DateTimeStamp

,A.Source

,A.TRANS_tambase_amt

FROM Engine_Prod.mc.WORKORDER WO

LEFT OUTER JOIN MSM.dbo.tblEngRunData ER ON ER.WONumber = ltrim(rtrim(WO.id))

LEFT OUTER JOIN mc.WORKTASK WT ON WO.wordoi = WT.wrkord_oi

LEFT OUTER JOIN mc.WORKORDERTYPE WOT ON WO.wot_oi = WOT.wotyoi

LEFT OUTER JOIN (

SELECT 'Labor' Source

,CHARGEINF.wt_oi

,LABORTRANS.tambase_amt TRANS_tambase_amt

FROM mc.CHARGEINF CHARGEINF

INNER JOIN mc.lbtr_chgs lbtr_chgs ON CHARGEINF.chgioi = lbtr_chgs.ref_oi

INNER JOIN mc.LABORTRANS LABORTRANS ON lbtr_chgs.owner_oi = LABORTRANS.lbtroi

WHERE LABORTRANS.posted = 1

UNION ALL

SELECT 'Parts' Source

,CHARGEINF.wt_oi

,INVTRANS.tambase_amt TRANS_tambase_amt

FROM mc.CHARGEINF CHARGEINF

INNER JOIN mc.intr_chgs intr_chgs ON CHARGEINF.chgioi = intr_chgs.ref_oi

INNER JOIN mc.INVTRANS INVTRANS ON intr_chgs.owner_oi = INVTRANS.introi

WHERE INVTRANS.posted = 1

) A ON WT.wtskoi = A.wt_oi

WHERE ER.DateTimeStamp BETWEEN @StartDate

AND @EndDate

AND WO.clsdt_date BETWEEN @StartDate

AND @EndDate

AND WT.ci_cnc_date IS NULL

AND WT.tmplt = 0

AND A.Source is not null

GROUP BY ER.EngEquipID

,ER.Location

,ER.Cycles

,ER.DateTimeStamp

,A.Source

,A.TRANS_tambase_amt

) B

GROUP BY B.EngEquipID

,B.Location

,B.Cycles

,B.DateTimeStamp

--,B.Source