The King James translates John 3:36 as:
"He that believeth on the Son hath everlasting life: and he that **believeth not** the Son shall not see life; (KJV)
However, other translations say:
He who believes in the Son has eternal life; he who **does not obey** the Son shall not see life, (RSV)
He that believeth on the Son hath eternal life; but he that **obeyeth not** the Son shall not see life, (ASV)
The Greek text behind the KJV does not differ from the Greek text behind the other translations. They all show the word translated as "believeth not" in the KJV and "obeyeth not" in the others to be the Greek "apeithon".
544 apeitheo (ap-i-theh'-o);
KJV-- not believe, disobedient, obey not, unbelieving.
As you can see, the translators of the KJV rendered the same Greek word in other places as "disobedient".
1 Pet 2:8
And a stone of stumbling, and a rock of offence, even to them which stumble at the word, being **disobedient**: (KJV)
1 Pet 3:20
20 Which sometime were **disobedient**, (KJV)
The translators of the King James Version translated "apeithon" John 3:36 as "believeth not" and in 1 Peter as "disobedient" and in another as "obey not"
(1 Peter 3:1)
They were not being inconsistent, rather, they thought of believing not and disobedience as interchangable terms.
KJV translations of the Greek (S 544) apeitheo
Rom 10:21 But to Israel he saith, All day long I have stretched forth my hands unto a
disobedient (S544) and gainsaying people.
1Pe 2:7 Unto you therefore which believe he is precious: but unto them which be
disobedient, (S544) the stone which the builders disallowed, the same is made the
head of the corner,
1Pe 2:8 And a stone of stumbling, and a rock of offence, even to them which stumble at the word, being disobedient: (S544) whereunto also they were appointed.
1Pe 3:20 Which sometime were disobedient, (S544) when once the longsuffering of God
waited in the days of Noah, while the ark was a preparing, wherein few, that is, eight
souls were saved by water.
Rom 2:8 But unto them that are contentious, and do not obey (S544) the truth, but obey
unrighteousness, indignation and wrath,
1Pe 3:1 Likewise, ye wives, be in subjection to your own husbands; that, if any obey not
(S544) the word, they also may without the word be won by the conversation of the wives;
1Pe 4:17 For the time is come that judgment must begin at the house of God: and if it
first begin at us, what shall the end be of them that obey not (S544) the gospel of God?