However one chooses to understand the apostolic words in John's famed Prologue, the theme of Messiah's glory is admittedly a prominent one throughout the Fourth Gospel: "This beginning of his signs Jesus did in Cana of Galilee, and revealed his glory; and his disciples believed in him"(John 2:11 WEB).
There is no doubt that Jesus displayed glory during his earthly existence, but this glory was derived as John 1:14 makes clear: "And the Word became flesh, and dwelt among us (and we beheld his glory, glory as of the only begotten from the Father), full of grace and truth" (ASV).
Irenaeus of Lyons correspondingly writes: "But what John really does say is this: 'And the Word was made flesh, and dwelt among us; and we beheld His glory, the glory as of the only-begotten of the Father, full of grace and truth.'" (See AH 1.8.5)
In fact, even prior to the Logos becoming flesh, he subsisted in a position of glory alongside the Father; but John does not necessarily say that the glory of the Son WAS the glory of the Father or vice versa.
Regarding the glory of the Messiah, the book Insight on the Scriptures (Published by the WTBTS) states: "Concerning Jesus' first miracle, the Bible says that 'he made his glory manifest.' (John 2:11) Glory here refers to an impressive evidence of miraculous power identifying Jesus as the promised Messiah. (Compare Joh 11:40-44.)"
As for John 17:5, Insight makes the following observation: "Jesus used the term [glory] to refer to the exalted state that he enjoyed in heaven before coming to earth" (Cf. Insight, 1:964).
The Insight book teaches us that the term glory must be defined in harmony with its literary context. It obviously does not mean the same thing in all contexts.
A number of commentators want to see allusions to the Shekinah glory in John 1:14. From this concept, it's often inferred that Christ is equal (consubstantial) with the Father. For example, Clarke's Commentary makes the following claim:
"And dwelt among us - Και εσκηνωσεν εν ἡμιν, And tabernacled among us: the human nature which he took of the virgin, being as the shrine, house, or temple, in which his immaculate Deity condescended to dwell. The word is probably an allusion to the Divine Shechinah in the Jewish temple; and as God has represented the whole Gospel dispensation by the types and ceremonies of the old covenant, so the Shechinah in the tabernacle and temple pointed out this manifestation of God in the flesh. The word is thus used by the Jewish writers: it signifies with them a manifestation of the Divine Shechinah."
But there might be other ways to explain a Shekinah allusion.
A) One could view John 1:14 as an implicative account that points to the prophet greater than Moses (Deuteronomy 18:15). Such an interpretation can be substantiated by considering the apostolic words recorded at John 1:17. Cf. 2 Corinthians 3:7-18; Acts 3:19-26.
B1) Another OT text that may be pertinent here is Exodus 23:20-26. It could point to Christ serving as the Angel (MAL'AK) of YHWH, that personal agent who carries out duties as the Leader of God's people through the spirit of YHWH. Personally, I do not believe that the Angel of YHWH is identical with YHWH since Zechariah 1:12, 13 makes a distinction between God and His angel. In that fateful passage, the angel poses a question to YHWH and God replies with comforting words. While one could argue that the angel simply functions as a mediating agent in this account (with no ontological implications), I do not think that this explanation tells the whole story. David L. Petersen (in his commentary on Zechariah) points out that the angel's words have a penetrating quality to them: "How long will you be without mercy for Jerusalem and the cities of Judah that have felt your anger these seventy years?"
B2)The text indicates that the Angel really is perplexed over the current state of Judah. He does not know what YHWH knows and so poses the aforesaid question to Him. The angel sees that seventy years have passed by and the whole earth is tranquil while God's people still appear to be experiencing the heat of divine anger. "How long," he wonders. By uttering these words, God's angel sounds forth a lamenting request that has been echoed by God's people throughout human history. If he is the preexistent Christ, then the biblical evidence would suggest that the Lord Jesus Christ is perhaps not consubstantial with the Father.