Zerk, propellers, needles, ECGM ... what are the functions of these?

I understand the basics of transfer case ... split power between front and rear axles/tires.

Differentials alter the balance between the two wheels on the front or rear.

But what is a "needle" and what does it do? And I thought I saw something about replacing the "needle" with an ECMG?

And propellers?

And what is the "zerk" access required for "needles"? And will my RCI transmission skid and cat shields interfere with it?

 

A needle is a type of roller used in a bearing.
The needle bearing is in the front drivers side different.
It’s the bearing the CV rides inside of in the differential.
You don’t usually have to replace the bearing unless you get vibrations.
This usually happens after you lift the truck. And it doesn’t alway happen.

The zerk is the fitting that you use to grease the propeller shaft.
The propeller shaft is also known as a driveshaft.

 

Regarding "what is a needle?": There are needle bearings in the front differential. The CV axles going from the wheel bearing to the front differential rest on these needle bearings (shown below on left). East Coast Gear Supply (ECGS) is a company that manufactures a solid bushing to replace the weak needle bearing and is a common point of failure when you lift the front end more than 2" (shown below on right).



And as I was typing this, smarty pants TnShooter already got you covered:

To add on to this comment, zerk fittings are where you connect your grease gun. Regarding the propeller shaft aka the drive shaft, you are greasing the needle bearings inside the universal joints (commonly shortened to U joints). Sometimes the zerk fitting is hard to reach as shown in the image below, but it's not all that difficult after you've done it a few times.



Re: "And will my RCI transmission skid and cat shields interfere with it?" On the rear shaft, probably not. On the front shaft, yes you will need to drop the skids in order to properly grease the driveshaft that turns the front wheels in 4WD mode.

 

Sweet! Thanks. I suspect I will have to deal with those eventually as a maintenance issue, but until then I will settle for that much knowledge.

 

And more thanks to @wi_taco for the picture-book approach (not joking). U-joints I am familiar with from my days of rear-wheel cards (3 FWD vehicles since, now 4WD ...) and that U-joint is what I recall.

EDIT: Having found a way to support the transmission plate under the car while removing the front (RCI has the same mounting bolts for both plates) I can easily drop one or the other or both now. Do not ask me how I learned the proper way to do that ...