So i was on the freeway today doin about 65 mph. I started hearing a hissing noise i guess would be the best way to explain it.So i pulled into town,i couldn't realy hear it in 1st or 2nd but 3rd to 5th it was very notice able.When i push in the clutch it goes away let it out it comes back.I can push in the clutch and rev the motor ang there's nothing as soon as i let the clutch out it seems to start instantly.I checked the fluid and it was very clean.Any ideas?

 

Wonder if its the clutch release bearing making the noise...Or I'm backwards on that one...

 

x2 on clutch release bearing

 

my truck just started that same thing on monday, it made it till wednesday and got really bad and started to clunk, I pulled my trany (nv4500) and pulled the top cover and every thing looked fine. So I brought it to a driveline shop today and Im wating to hear if its even coming from my trany, If not in the trans i think it might be in the t case. Clutch looks good. Ill let you know what I find out

 

Sure it's not boost leak?