First, I need to know what size the u-joints are.
Then, I need to know if I replace them, is it necessary to balance the drive shafts?

 

What size? who knows...LOL get spicer units I think they might all be the same. I think mine are..never any need to re balance shafts after ujoint change.

 

As long as you mark the Shafts so they go back together the same way they came apart balance will be fine. Size wise go to the parts store tell them what you have and they will get you what you need.

 

There seems to be 2 different widths, unless they are different for 5.4 and 6.8.

 

Likely a 1350 series you dont mention what vehicle your working on. No rebalance not required unless you currently have a vibe.
To find out what you have run the vin of the truck by your local Ford dealer parts counter. Or remove the joint and measure. Or bring shafts to a shaft shop they'll know just by looking. Spicers are the better ones. Use the Spicer grease. If you have not ever performed this before read up and youtube. Its easy to mess up a yoke if your a first timer. If you are in fact a newbe and are apprehensive or lack the tools IMO look for a drive shaft shop in your area...Fleetpride? Drop the shaft yourself and bring it in. Carefully mark its orientation on either end so it goes back in the same way it came out. Less likely to have a vibration issue that way. A shaft shop wont charge you much to R&R ujoints and it will be done quickly and properly. If your handy its not too bad a job for a first timer WITH the right tools. Pay attention to the ujoint bolts and straps(if equipped). Replace if needed, they're cheap. Also clean the saddles or flanges and bolt threads and use a dab of blue loctite on the bolt threads.
One more thing if its a two piece shaft regrease the slip splines with Ford grease. Not sure if either one of the vehicles you have listed have this problem which was more prominent on 08s and up. Search here of google it as we have covered this procedure many times.

 

It's my '99 F-250 SD Supercab long bed Lariat V-10. It is a 2 piece shaft.
I can't do the physical work under the truck, (Heart issues), so I have to get a friend to do it for me. It's been decades, since I replaced a u-joint.
I may as well replace all of the u-joints and the carrier assembly, so it won't have to be done again. It now has 90,000 miles on the truck.
I now have 74 years on my body and my undercarriage is in disrepair.

I've been searching for the thread that mentioned the carrier torque but can't relocate it.

Spicers website shows a Spicer No. (5-160X greasable) and a Spicer Life (5-1410X non-greasable) for the 6.8 and a Spicer Life (5-3616X), if it's an aluminum shaft.
And 211359X, for the carrier bearing.

http://www2.dana.com/expertforms/dek350.aspx

 

I would only use spicer life joints...I cut the center out with a torch and air hammer the ends out...keeps me from ruining the flanges. I don't use a vice or hammer any more. Using a torch make disassembly a breeze.

 

I suppose I could use my hydraulic press, to remove the caps.

 

1350 u joint I believe.

As far as get out ...well if in the front you could have six point bolts holding the straps on. Clearance is a real issue with that and using a good 6 point socket. It is 5/16.
Once out press or vise? A press will work but a real pain in the ***. Utilizing sockets that are smaller than and larger than those caps to push it out ...the. repeat another size. You run the risk creating some nasty burrs and such.

If you have access to a fire wrench, oh dear lord that is the best and easiest way to get that ignorant thing out. You can burn the body out...then you can even burn a hole right in then center of the remaining cap. At that point it may even just fall out.

 

The carrier needs to be pressed on and off......but at 90k I wouldn't bother unless there is an issue. Mine went 430K before it started to grumble..:::::: and I'm STILL on the original ujoints at 443+k.

 

I used this: http://http://www2.dana.com/expertforms/dek350.aspx

I stopped by the distributor to get some u-joints and spoke to the shaft assembler.
He said $40 to install new u-joints and carrier.
I had a friend remove the shafts, today and will take them over Monday and get them installed. I'll report back, when I get them back and see what the final bill is.
Then, I'll have my friend re-install the shafts.

I'm 74 and I hope they outlast me.

 

$178 for the u-joints and center bearing, installed.
That included clamps, bolts and raising the spline on the slip yoke.