By skopiec on Monday, October 15, 2001 - 11:00 am: Edit

In doing a post off-road inspection and cleaning, I noticed that my rotoflex is starting to develop some small cracks. Are some cracks normal, or is it time to change out when any cracks appear?
It looks like the previous owner had replaced the coupling about 25K miles ago - is that a normal lifespan?

I also have some mild vibrations when coasting down from speed, could this be contributing?

Thanks for helping out a newbie (but I'm learing quick!)

-Scott
'96 SD
52K Miles

By gp (Garrett) on Monday, October 15, 2001 - 11:56 am: Edit

yeah those things supposidly have a habit of cracking within 30k from what i have heard here and the dealer. mine from what i can tell from my records is original at 63k and looking good. if the rotoflex is torn it certainly can cause a driveline vibration.

if you think you would like to upgrade there are some folks here that have replaced the rotoflex with a much stronger U joint.

By Discosaurus (Discosaurus) on Monday, October 15, 2001 - 12:11 pm: Edit

""It looks like the previous owner had replaced the coupling about 25K miles ago - is that a normal lifespan?""

No - not in my opinion and experience.

I replaced my original RotoFlex at ~50K miles and still carry it as a spare. It shows no sign of damage.

I run a 3" lift, $G HD trailing arms (which correct the pinion angle to some degree) and engage in off road activity that would probably be considered much more severe then "average". Oh, I also run a manual gearbox which places a lot more stress on that flex coupler then a slushbox.

keith
discosaurus

By peter matusov on Monday, October 15, 2001 - 12:35 pm: Edit

the rotoflex has three arc slots, and it can be installed in two ways - such as the slotted portions are compressed under torque (while going forward), or extended. They should not be compressed under torque, and my dealer doesn't know that or pretends that it doesn't matter. They replaced the roto, and it failed miserably 23k later. The original joint lasted for 66kmi.

You're looking into spending about $100 on the rotoflex and bolts, and do it yourself and do it right.

peter

By skopiec on Monday, October 15, 2001 - 01:52 pm: Edit

Peter

I've been doing some research on replacing the rotoflex, but this is the first time I've seen reference to the arc slots - thanks for the tip! No mention of this in the WS manual either.

I assume that the orientation will be obvious when I get around to replacing it.

Scott

By lynden on Monday, October 15, 2001 - 02:40 pm: Edit

Am I missing something? Why doesn't he replace it w/ a u-joint? Aren't u-joints preferred over the rotoflex? Maybe I don't have things straight though???
Lynden

By me on Monday, October 15, 2001 - 02:43 pm: Edit

ujoint = money
replace roto = less money

By lynden on Monday, October 15, 2001 - 03:02 pm: Edit

Good point!!!
Lynden

By p m on Monday, October 15, 2001 - 03:20 pm: Edit

Lynden,

the rotoflex is not that bad of a design, it does eat up a lot of vibration and torsional shock loads. From the sheer strength point, a common U-jointed shaft would be better, but you'd be transferring the same load onto the diff and transfer case. The roto is actually a true CV joint, unlike the U-joint; if you're unlucky, with 3" of lift you may need a U-joint/CV joint'ed rear driveshaft to avoid bad vibrations (mucho dinero).

Scott - when you get to replace the roto, the beat-up joint will clearly show you where and how the load is applied.

peter

By Slider on Monday, October 15, 2001 - 10:15 pm: Edit

my rotoflex is at 85K miles...
last 5K w/lift...

When I first started inspecting the thing, I took it off and got rid of all the undercoating overspray (I think that's what it was)...which can make it appear cracked and deteriorated.

I'm waiting with a "U" replacement driveshaft from a RR but that stupid rotoflex still shows no wear...

I don't get it??

By Jake on Saturday, October 20, 2001 - 10:52 pm: Edit

237K, still on original Rotoflex.......and yes, it does go off-road

By PHILLIP on Sunday, October 21, 2001 - 12:51 pm: Edit

WHat the hell is ROTO FLEX

By Mike Rupp (Mike_Rupp) on Sunday, October 21, 2001 - 02:25 pm: Edit

Phillip,

The rotoflex is the rubber donut that is used in place of the rear universal joint on your rear driveshaft. It is supposed to take some shock out of the system.