I checked my rotoflex and it shows cracks around the bolts, so it needs to be replaced. Also the drive shaft doesn't grease well anymore, and I want to replace it completely since I don't have time, tools and skills to replace the U-joints. Also, the conversion kits (AB, lucky8, BPU) are cheaper than a rotoflex + drive shaft. Is there a disadvantage doing the conversion?

 

Any shop should be able to replace your u joint and rotoflex in less than a half-hour. It's a super-easy job. Almost anyone could do it with a vise, hammer, some wrenches and a youtube tutorial. No need to replace driveshaft or convert unless you do hard-core rock crawling with your truck. The rotoflex is a good "fuseable link" to protect the drivetrain from more expensive damage IMO..

 

The rotoflex is there to absorb excess force placed on the differential via the drivetrain. It’s there for a reason, I’m Team Keep-it-installed. It’s a super easy replacement, the truck doesn’t need to be lifted. It can be done easily with all four wheels on the ground. Be sure to chock the tires btw. I did it in a hotel parking lot with very limited tools. Takes about 30 minutes for a first time. Just crawl under the car, unbolt the existing nuts/bolts, push drive shaft toward the front of the car, remove and replace with the new one, push driveshaft toward rear of car, install new bolts/nuts. Done.

Oh, just make sure the embossed arrows in the rotoflex point at the flanges. They also indicate bolt insertion direction.

 

Thanks, that makes sense.

I am not worried about the effort, since I do most of the repairs myself. But I have never done replacing U-joints, I have to look into this. Shop is not an option, since they charge in my area $200/hour. For that money get a lot of parts.

What's a good brand/source for U-joints for the rear drive shaft?

 

Anything will be fine for a stock setup as long as it is grease-able. Rock auto, call Eric @ Lucky8(discounts forum members), Atlantic British, etc.

 

Are the GKN U-joints recommended?

 

Precision/Moog 344... I could not find the GKN in my area but this one works just fine. remember to take the zerk out before you try to pound out the old one. Super easy job...

 

YES!
IMHO spend the few extra dollars and get the GKN HD's ( TVC100010G ) with the metal caps.
> https://www.lucky8llc.com/products/r...iversal-joints

 

So I replaced the rotoflex (GKN, made in Germany) and the U-joint. Getting the shaft out was easy, U-joint too. Getting the new U-joint (TVC100010G) in was a PITA, one cap cracked when pressing it in. I had to get a replacement quickly, only option was O'Reilly (Precision). I sanded the holes with 1000 grit sandpaper, but the new U-joint got stuck again. It came out easily, so sanding again and finally got it in. was very helpful, especially the trick with the hammer to get it set in correctly. Took a test drive, no vibrations and after a 600 miles trip, no issues.

Here is a close up of the old rotoflex. The cracks are barely visible.



... but after squeezing it a little bit, there were deep cracks visible. Compared to the new rotoflex it felt like a sponge almost.