Is a worn throw bearing manifested by shaking in the transmission upon engaging the clutch? Could I have another problem (other than the throw bearing)?

Lastly, how much does a new throw bearing cost (and how long does it take to install)?

The throwout bearing is a $20 part that requires 10 hours of labor to replace

You must pull the transfer case and transmission.

Is it only shaking when cold, or all the time ?

Well, it occurs when cold or when I'm on an incline. I will try to pay more attention to conditions in the next few days, but I am pretty sure that's when it's happening.

Let us know if it is in the clutch pedal, the shift lever or the whole truck that is vibrating, and what part of the shift/clutch engagment.

It was the whole truck shaking, right as the clutch is beginning to engage, through when it is about 3/4 engaged. It has only really been happening when it is cold.

Can you pop open the inspection cover to see how much of the clutch pads are left?
If you wheel your rig alot, you will definitely go through the clutch more quickly.
Often if the clutch gets wet, or worn down, it can grab and slip quickly causing the driveline to shake. It will translate through the whole truck and make for a rough ride.
Is it mainly in 1st, or does it happen in every gear at around the same RPM?

Rob

Throwouts can be a royal PITA to replace if you've never worked in that part of the vehicle before. Its not hard to do, but it can be time consuming if you dont have the right equipment. Make sure either you have a lift, or rent a tranny jack (I have no idea if you are still within warranty or not.).
If you're out of warranty though, and you have the tranny out, I would definitely suggest going with a Centerforce clutch while you are in there and have everything apart.

Rob

It's only in first, and only when cold. I know it's not the clutch itself - I've had that problem and it just feels different. That's more in the pedal and the clutch, rather than this (this feels more like the WHOLE TRANNY).

Anyway, I am going in for a service soon anyway, so I will have them check it out. It has about 53k miles on it.

Could be a bad rear main seal, which contaminated the clutch disk. That will cause shuddering when taking off from a stop.

The thing is, though, it doesn't happen all the time. It only happens once in a while, and only when the vehicle is cold. It's exacerbated by more weight in the vehicle (usually several passengers), but still only happens after the vehicle has been sitting for at least a few hours.

Doesn't a contaminated clutch due to rear main seal leakage cause the shuddering any time the clutch is being engaged?

It sounds like classic clutch shudder. This happened to my last Nissan pickup, possibly because I'm very easy on the clutch. If you can get past the shudder with a little bit higher RPM's on takeoff, you might find it goes away after a few more weeks.

Yeah, I've noticed it comes and goes. Every time, I pray it's not the throwout bearing. I guess I just need to drive more "vigorously".

I was having that problem. It was the pilot bushing. Nissan wouldn't cover it under warranty. I had a new clutch, pressure plate and throw out bearing put in since it was apart.

What's the difference between the roller pilot bearing and the throw out bearing?

The pilot bearing is in the back of the crank and keeps everything lined up so the clutch surfaces are at 90 degrees and engage properly. If the pilot bearing is worn, shuddering can result.

The throwout bearing is what interfaces between the spinning driveline and the stationary cluth pedal. If it really really wasted, enough to induce an imbalance, it might cause a problem, but it's unlikely since it won't be free to move when it is under load, as when you are letting the clutch out.

That's the difference.