Crazy noise in neutral

[zomotropin]

i have noticed an interesting noise from my truck when it is in neutral, it sounds something like an air gun. it doesnt happen everytime i put it in neutral. sometimes the noise starts as soon as it goes into neutral and some times it takes a few seconds. my transmission seems to be working well i havent noticed any other problems.

[joe]

Manual/auto trans? Year/model vehicle?

[zomotropin]

oops! yes that my be important it is a 78 j10 auto th400

[Joe Guilbeau]

What does an air gun sound like?

[zomotropin]

it sounds like a high pitch squeal/grind sorta