I have a 1996 Trooper. It makes a whinning sound in every gear except 4th. What could be causing this?

 

It sounds like an input shaft bearing

 

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everygear except 4th an 5th is.........caused by at some point in time the fluid got low an 1st 2nd 3rd gear was starved of oil.manual trans right?isuzu has a protective coating on those gears actually all gears for noise,when this wears away they get noisy.check your fluid level if its low in the trans an overfull in the transfer case thats where it went.the seal between the 2 halves is bad.to fix this problem is to replace gears syncros blocker rings bearings.an the bad seals of course. if its not too bad an still able to shift an drive try adding trans fluid additives LUCAS work very well.your hearing the whine in those gears because of powerflow.its the loudest in 1st an gets quiter on the way down.goes away in4th 0r 5th,cause powerflow then is straight through an notdown passing along the counter shaft,sometimes even that has to be replaced,