What is the biblical basis for the JW belief that only 144,000 go to heaven?

Not wishing to re-invent the wheel, I will not repeat the biblical basis in user9485's answer regarding the Jehovah's Witness doctrine that only 144,000 people will ever get into heaven, that number being culled from the time of Christ up until the still future point at the great tribulation, when JWs say the 'heavenly calling' will end, all those remaining on earth with that 'calling' suddenly dying and being whisked up to join Jesus in heaven. However, allow me to put a spoke in - one that is missing from the JW Wheel of Theology so far presented.

Nowhere in the Bible does it ever say that "only 144,000 ever go to heaven", as in your question. When asking for "a biblical basis' for any doctrine, you will always get one from those who hold to that doctrine. Thus, the JWs have anticipated the problem you raise, namely, that Revelation describes two distinct groups of people in heaven, worshipping before the very throne of God in heaven: the great crowd that is innumerable, humanly speaking, taken from all nations and having come out of the great tribulation, then the 144,000 taken from 12 tribes of Israel and 'redeemed from the earth'.

This is the spoke in the wheel, for when a huge number of people are depicted as dwelling in heaven, of which a particular group of 144,000 forms but a part, then the only way any doctrine could be formed on the basis of other scriptures would be to so interpret those other scriptures as to dispense with the 'inconvenience' of Revelation chapters 7 and 14 saying there's a huge number of humans in heaven. That is why a critical step in persuading JWs to accept the 144,000 only doctrine is to explain away the great multitude as only being symbolically in heaven, worshipping, and not literally being in heaven. This means that the verses about the 144,000 worshipping in heaven require that number to remain literal but the humanly uncountable number to be symbolic.

Anyone taking a bit of a verse as literal, but the rest as symbolic, does not have a biblical basis for any resulting doctrine. This is the spoke in the Revelation wheel with regard to how many humans are in heaven. To go on at great length about Jesus' parables, claiming many of them support this doctrine, is back to front, because the number 144,000 occurs only twice in the entire Bible, both times in the book of Revelation. That is where biblical truth about them must start, and any other biblical points claimed in support must always agree with what has been said about this specific group in Revelation. If so, then there truly is a biblical basis to be claimed, but if not, then interpretation about the 144,000 has failed to be consistent with what the Bible actually states about them.

I have the JW book "What Does the Bible Really Teach" and agree with the question as to what their doctrine states - but their book evades the problem in Revelation that you flag up (as an example). The answer given by user9485 first presents the JW formula for interpretation, then claims that because there are distinctions between the 144,000 and the great crowd, this must mean that they are in different locations. The first point is back-to-front (as Revelation must be examined and believed first), and the second point is illogical. The following points about parables are beside the point, given the errors of the first two points, and the last point alludes to a teaching about "a future covenant" for those 144,000 in heaven. Is that a JW one, or that of another group which has similar beliefs, though with variations? That may be beside the point. Sticking to the remit of your question, I would say that user9485's answer deals with main parts of it, but the missing spoke is trying to make lots of other Bible verses appear to fit with a doctrine that does not actually have Revelation chapters 7 and 14 as its foundation. This makes for a rather bumpy biblically-interpreted 'ride'.