Really no other words for it. When starting from a stop, the clutch will sometimes groan as I let the clutch pedal out. If I bump the accel pedal quick before letting clutch out, no groan. Quick history, about 60k miles ago, I had a HD clutch put in, but the master and slaves were not upgraded. I was having trouble shift so I took it to a recommended trans guy and he said he thought the slave was giving out. I put in a HD master and slave and that is when the groaning started.
Clutch does not slip. Shifts with ease. Fluids are full.
Is it possible that the slave cyl. is not completely retracting? Maybe the nylon strap that was on the slave piston it some how in the clutch? I resitate to pull the slave because I am not sure if the piston unseat and/or how easy it goes back in.
2002 5.9l 5sp 2wd

 

I have never heard a clutch problem described like that.

Is there any chatter or other symptoms of slipping? I.E. odor, u-joint clatter, shaking etc.?

Could it be the bushing on the clutch pedal shaft?

Outside temps unusually low...

Old dog in the passenger seat!? Your old knee...

 

Six, although my knees are getting bad...LOL
No slipping. No burning smell.

Is it possible the fly wheel or clutch disc may be glazed similar to how brake pads and rotors get?

Aside from the occasional 1 sec groan, all is normal.

 

I can usually tell when I have stressed/slipped my clutch when backing a work trailer up a small hill to park it and I chatter it going around a slight curve on the pathway. I have 3.54 gears so I get a slight struggle as I have to feather it a bit to keep from going in too hot.

The next few standing starts will sometimes chatter just a bit and then it clears away, I am thinking this is maybe a slight glazing wearing off...

I would consider checking your u-joints. They can make weird noises when going out....

 

I also have 3:55 rear axle. I would completely understand the groan if it only occurred with the 11K pound goose neck behind it, but it does it empty too.

 

I'm still leaning toward u-joints....

 

Guess it is possible,but had the drive shaft rebuilt and balanced 2 years ago. 3 new u-joints and new carrier bearing.

 

My last "professional" rebuild of the shaft lasted about 50K miles.
The stockers went about 75K.

My latest repair was by the local driveline guy and he suggested solids, as they are stronger, and said I should get 100K out of them, sees it often...

How many miles since? That's a dozen caps to get right....

 

Let me understand what the "groaning" noise is you're describing..... Does the noise sound like its coming from under the dash by the pedal or does it sound like its coming from outside the cab and under the truck? If its in the cab then you're either hearing the clutch pedal mechanism joints needing a spritz of spray lube. If the joints aren't it but its still coming from under the dash then it could be the master cylinder. About 5-6 years ago my master cylinder was groaning (thats actually the noise it made) when I'd press on the pedal. Not all the time but becoming more often and more annoying. After pin pointing what and where the noise was coming from I realized that it was the master cylinders plunger making all the racket. So instead of quickly going out and buying a replacement, I took some PB Blaster spray (since its good for rubber), pulled back the clutch switch on the master cylinder shaft, pulled the plastic cap covering the MC opening, and generously sprayed some PB in there. Worked the clutch and sprayed it again. It hasnt made that noise ever again.

 

there^ that's a good, cheap place to start.