I have just recently noticed a very noticeable hissing noise when the clutch pedal is all the way out. If I depress the clutch the noise dissappears. I notice the hissing when I am driving down the road as well and it also disappears when I press the clutch to change gears. Any Ideas???? It doesnt have any negative effects (Power, torque) on the truck.

 

possibly a throw out bearing. they usually stop when you press the pedal

 

Ok...does it need to be replaced or is it just starting to wear out

 

It could also be the throwout bearing is not fully releasing from the pressure plate fingers so you hear it rubbing. You should look into it to make sure it is releasing fully.

 

whouldn't it be grinding?

 

On two other vehicles I own with old school mechanical linkage adjustments, that is the exact noise I would hear unless I got the clutch adjustment just right to allow the throw out bearing full release from pressure plate. Otherwise, a slight contact to throwout bearing would cause it to still spin and make a hissing noise (and prematurely wear out the bearing if not corrected). If you get under the trans with truck idling you MAY be able to hear the contact. Easy to hear with gas motors but maybe not with the diesel rattle.

 

I had the same symptoms early this year. I can't remember hearing it while driving, but my early 99 is plenty loud enough to cover up most other noises. Unfortunately my clutch went out in probably less than a hundred miles after I started noticing the noises. Bad throw out bearing had taken out the pressure plate.

 

That's a big tranny don't try to tackle it by yourself. It took me and a friend about 3 hours to pull his out one day and about 4 to put it back in the next. His clutch fork broke

 

Yep, throw out bearing and/or rubbing the teeth on pressure plate. Did min a few months ago. Same sound.

 

Yep. Mines out at the moment. Two people, two floor jacks, and two ratchet straps. MAKE SURE it doesn't fall off the jack!

 

It's easiest to use a tranny jack.
You can also get an adapter that will mimic a tranny jack and it will fit a floor jack.

 

If I was going to replace throwout bearing should I replace the clutch as well while the tranny is out?

 

Yes you should replace the clutch, pilot bushing/bearing, pressure plate, and throwout bearing when you have it out. You may also look into a new throwout arm if you have one of the older ones as they were known to bend. The new ones are redesigned and heavier duty. Also depending on what the flywheel looks like, you should plan on having it resurfaced too.

 

Dan- That's cheating! Nice setup. Can you easily tilt front to rear? I can by just barking orders at my friend Ron on the other jack!

I've loved that picture since the day you first posted it.

Rob- How many miles are on it? If the fingers on the pressure plate are all worn in you'll know. If there's a bunch of parts that fall out you'll know. If everything looks great, then maybe, just maybe if it's low miles just replace what's obviously worn out. But in all likelihood you're looking at replacing the whole enchilada, even then you're not guaranteed to get rid of the hiss. The hissing isn't one I've heard of, but neither is my condition where the engagement is all up at hte top and basically on or off- no ability to modulate/feather it.

 

Heres what I have for my floor jack, works like a charm.

Torin Big Red Transmission Adapter for Hydraulic Jack, Model# TRE2001