Here is a How to Grease your Slip Yoke Without Removing the Drive Shaft. This remedies the bump/clunk that happens in the drive shaft (two piece) when accelerating/decelerating.
This was performed on a 1999 Ford Ranger 4x4. Procedure will be very similar
with other year Rangers as well as Explorers and possibly Mustangs.
Flat Head Screwdriver
Latex Gloves (if not using a grease gun)
1. First locate the slip yoke boot. It should be located near the
front of your truck near the catalytic converter.
2. Pry off the metal clamps on the boot with a flat head screwdriver.
They should pop off (break) easy, be careful not to damage the boot.
3. Pack the slip yoke boot with grease of choice. I used Valvoline ($4.79)
blend purchased at Checker Auto Parts. It was made for Fords, so that
is what I used.
4. Use zip ties to secure slip yoke boot back onto drive shaft. You could also
use hose clamps, but I didn't since I didn't want any chance of
unbalancing the drive shaft.
I took it out for a quick spin and bump/clunk was completely gone. Note that you will have to re-grease down the road, but with decent grease it should last a good while. Others have had similar results adding Jim Duff traction bars and not having to worry about re-greasing. This was truly a quick fix, took about 10min total. Suggestion/Comments are welcome.