Jehovah in the Old Testament and Jesus in the New Testament are one and the same.
1. Jehovah is the only saviour
OT - Isaiah 43:11 ~ I, even I, am the LORD [Jehovah]; and beside me there is no saviour.
Jesus is the Savior
NT - 2 Peter 3:18 ~ But grow in grace, and in the knowledge of our Lord and Saviour Jesus Christ. To him be glory ... for ever.
NT - 1 John 4:14 ~ And we have seen and do testify that the Father sent the Son to be the Saviour of the world.
2. Jehovah is the only God and Saviour
OT - Isaiah 45:21 ~ there is no God else beside me; a just God and a Saviour; there is none beside me.
Jesus is both God and Saviour
NT - 1 Timothy 2:3 -5 ~ For this is good and acceptable in the sight of God our Saviour ... the man Christ Jesus.
NT - 2 Timothy 1:10 ~ But is now made manifest by the appearing of our Saviour Jesus Christ
3. Jehovah is Salvation
OT - Isaiah 12:2 ~ Behold, God is my salvation; I will trust, and not be afraid: for the LORD JEHOVAH is ... my salvation.
Jesus is Salvation
NT - Acts 4:10 -12 ~ by the name of Jesus Christ of Nazareth, whom ye crucified ... Neither is there salvation in any other: for there is none other name under heaven given among men, whereby we must be saved.
NT - John 4:42 ~ And said unto the woman, ... this is indeed the Christ, the Saviour of the world.
4. Jehovah's Glory is Exclusive
OT - Isaiah 42:8 ~ I am [Jehovah]: that is my name: and my glory will I not give to another, neither my praise to graven images.
Jesus is the Lord of Glory
NT - 1 Corinthians 2:8 ~ for had they known it, they would not have crucified the Lord of glory.
NT - Hebrews 1:6 ~ And again, ... he saith, And let all the angels of God worship him.
5. Jehovah wants only himself to be worshipped
OT - Exodus 34:14 ~ For thou shalt worship no other god: for the LORD, whose name is Jealous, is a jealous God:
Jesus is worshipped
NT - John 9: 38 ~ And he said, Lord, I believe. And he worshipped him.
NT - Acts 7:59 ~ And they stoned Stephen, calling upon God, and saying, Lord Jesus, receive my spirit. (Stephen prayed to Jesus)
NT - 1 Tim. 3: 16 - ~ And without controversy great is the mystery of godliness: God was manifest in the flesh
Mystery Solved.