03, Gas motor, 4X4, manual. Depress the clutch..clunk. Shift... clunk. Slow in reverse..clunk, clunk, clunk. Not much technical info I know. Had a guy look under the truck one day, he said it was the transfer case bouncing around. Another guy said it sounded like it was a heavy throw out beraring. Some times when it does it, like in reverse, the truck will bounce some, or shudder. There is no support under the transfer case, like a cross member. I had the dealership look at it when I first noticed the noise, they said they found no problem. A year later, the noise is still there, just wondering if it is in fact normal, or what it is.

 

My truck makes the exact same noise. My 99 4x4 F2 did too. You can rule out the transfer case because my truck has less transfer-casage than your truck. I don't think it's the splines on the driveshaft because the splined part is way in the back near the rear axle on my truck and the noise is coming directly from under my seat. (2-piece driveshaft on a reg cab? Dude, that's completely ridiculous.) I think what happens is that the engine/transmission assembly rotate axially when you release the clutch and the sudden lack of load and torque makes the whole thing rotate axially and hit the bump-stop strap on the transmission mount. Also the springs on the clutch disk makes it bounce axially to some extent too. Moral of the story, shift and disengage the clucth smoothly. (Because it never makes that noise when I shift carefully or give it just a bit of clutch when backing up.) I also get the abominable wheel-hop under harsh acceleration but I'm planning on getting some Deaver 3" lift spring packs to fix that, as well as a one-piece driveshaft.

 

Hang 10,explain your post a little better.
are you sitting still in your truck(not rolling) and depress the clutch,getting ready to put into gear ??????? Is this when it klunks?
or are you shifting the gears as you would normally to take off????? is this when it klunks?

This latter situation is normal but can be lessened somewhat
slip-joint lube
clutch springs in disc wearing
internal play within the 6/5 speed tranny
internal transfercase chain slop (stretched)
u-joint wear
internal backlash in the rear diff out of spec (ls rearends get this quicker than open)

But if you have a klunk when sitting still , you may have a bad pressure plate and clutch springs .the diesels are common with this because they have more torque.
A bad throw out bearing usually makes a whine or whurring sound when releasing the clutch pedal.

I have seen a bad input bearing on 6 speeds cause the front input shaft wear the gears internally.They replaced my 6 speed 1 week after I got my truck back in 02 for this .

Just my $.02 on this
on edit I failed to mention that you have a hydraluc slave cylinder for this truck(clutch) it can be binding or the connection to the thowout arm misaligned or even a bent arm itsself.
Rich

 

I wish I could explain it better, i'll give it a shot. Depress clutch, start truck. Release clutch..clunk. Drive in 1st to stop sign, depress clutch to stop..clunk. Engage 1st to go up the street, depress clutch to shift from 1st to 2nd,..clunk.

In reverse. Depress clutch to shift into R..clunk. Depress clutch to come to stop in reverse..clunk..bounce..clunk clunk clunk. (bounces with each clunk). Repeat forward gears.

If I am in a parking lot with people out and around, it is loud enough to draw their attention to it. It isn't a quiet little thump, it is a loud 'clunk'. Sorry I don't know how else to describe it. I have had manuals in most everything, never had this noise. Like I said, it has happened from the day I bought it new with 0 miles on it. I have looked under it myself and had my wife sit in it and clutch it. It looks like what the one guy told me, it looks and sounds like the transfer case bouncing around. Like I said, I took it to a dealer that has an excellent reputation for service (not where I bought it). While they could duplicate the noise, they said it seemed normal, so I never pursued it further. I know this transmission is very loud and sounds like a UPS truck when it starts out. Loud enough that people on the sidewalk turn and look if you are coming up behind them. I thought noises were just the nature of the beast. Now I am not so sure..

 

I think there's two types of klunks here. The noise it makes while disengaging the clutch in reverse "clunk..bounce..clunk clunk clunk" is a different kind of "klunk" (sharper, more like a "bang") than the "klunk" you get while letting the clutch pedal back out quickly which is a more muffled sound or softer "klunk" right? The first bouncing type klunk is still the transmission bouncing on it's mount but the second type of clunk is more of a mystery. You'll notice that if the engine is running and you release the clutch fast, it makes the sound, however, if you shut off the engine, you can release the clutch pedal as fast and as hard as you want, it doesn't make a sound. So that eliminates the throwout arm and bearing. (Otherwise they would klunk at all times) What else could it be? Either the springs on the clutch disk that are hitting their seats or bottoming out or the fact that the input shaft is abruptly made to spin again and it's the sound of gear lash being taken up between the input shaft and the countershaft. I'm betting on clutch disk noise. Maybe a better quality clutch might solve the problem. I'll let you know in 110,000 miles.

 

Mine does the same. I had some one else sit in the drivers seat and I watched underneath while they duplicated the situation. When the noise occurred, I noticed that the rear axle would rotate upward and back down several times (slightly). Rotating the axle is the same as the tires turning(at least as far as the drive shaft is concerned). When the rear axle rotated up, the driveshft turned slightly one way and when the axle rotated down, the shaft turned the other way. The noise is coming from the transfer case. My theory is that the drive shaft rotating one way then the other, is showing me the amount of play in the transfer case.
Now that I think I know whats going on ....... I don't know if it needs to be fixed. I think greasing the splines may help some. There may be some noise attributed to the drive shafts as they will become shorter when the axle rotates up and so on....... Just a thought.

 

I wish we could get you guys in a room to explain the clunking/klunking on video. Would make for a clunking good time.

 

Maybe an infomercial.

 

Lock your wheels and put it in 4X4 high range and give it a try on dry roads. If the noise is almost gone then it is just the backlash in the tranny and transfer case. The 87-99's were worst for this. My 94 250 4X4 5spd sounded like it was going to explode the drive-train all of the time and I managed 450,000 + km without a tranny rebild and one chain replace in the transfer case. BTW: Used synthetic oil and changed it every 25,000-30,000 km.

Tim ------>> I miss that truck.....

 

Sure sounds like u-joints to me. But I guess you have already checked them. Do you have any vibration or humming at high speeds. .If you do I would guess u-joints/driveshaft's/splines.