Why no single cardan drive shafts?

Pretty Fly

Pretty Fly

New member
Hear me out here. All of the aftermarket driveshafts for JK's seem to be double cardan on the transfer case side and single at the axle. This type of drive shaft requires us to point the pinion in line with the drive shaft as much as possible. On the front this means sacrificing caster to keep the drive shaft from vibrating. On the rear, we end up bowing the coils if we aim the pinion up. I know there are solutions to these problems but would it not be simpler to run single u-joints at both ends of the shaft and split the angle difference between both ends the way this type of driveshaft is supposed to operate? Say 5 degrees or so at each end. I did some research on the double cardan shaft and I read that it doesn't even allow much more maximum angle than a single. I'm tempted to have shafts custom made. Thoughts? In case you haven't seen this before, I thought this video was great.
http://youtu.be/gmV4qwLfOMY
 
Good question!
I had the same thoughts when installing my lift and double cardan front drive shaft. Your video is very interesting, hope somebody has more info.
 
I totally agree. The shafts on the front are nearly 4' long and there is no way you are going to get them really bound unless there is some crazy articulation. Even so it would likely be at a slow speed.

I used the double knuckle shaft on the rear of my yj because the driveline is about 24" or less. It has a single up front with no problems. I also bypassed the vacuum disconnect and it spins constantly just like tj's and jk's.

I was thinking of a custom made single at my local driveline shop as well.
 
Pretty Fly said:
Hear me out here. All of the aftermarket driveshafts for JK's seem to be double cardan on the transfer case side and single at the axle. This type of drive shaft requires us to point the pinion in line with the drive shaft as much as possible. On the front this means sacrificing caster to keep the drive shaft from vibrating. On the rear, we end up bowing the coils if we aim the pinion up. I know there are solutions to these problems but would it not be simpler to run single u-joints at both ends of the shaft and split the angle difference between both ends the way this type of driveshaft is supposed to operate? Say 5 degrees or so at each end. I did some research on the double cardan shaft and I read that it doesn't even allow much more maximum angle than a single. I'm tempted to have shafts custom made. Thoughts? In case you haven't seen this before, I thought this video was great.
http://youtu.be/gmV4qwLfOMY
Click to expand...

Actually, JE Reel has been thinking about offering one for the rear. The benefit would be more for cost savings to the customer than anything. Don't think you can really do this up front though especially being that the output shaft sits at such a steep angle (more so on 2012-up). Ideally, you want the output shaft and pinion to sit parallel with each other and that would be hard to do without having a significant amount of positive caster.
 
I wonder if anyone knows what angle the front transfer case output sits at on 2012+. On my 2014 it appears to actually point up. If that is so, one would have to have a pinion at a slight down angle to put the yokes parallel to one another. As Wayalife just commented, that would be a lot of caster, maybe 7 or 8 degrees. I just wonder if you still could find a better compromise. My front driveline sits at a 6 degree angle. To run a double cardan shaft as suggested, I would need +6 degree pinion angle and 0 caster. Not trying to start an argument at all, I just think we can do better. Maybe I should just solve all problems with a pro rock 44. If JE Reel wants to do a two u-joint rear shaft, I will be their first customer.
 
Pretty Fly said:
I wonder if anyone knows what angle the front transfer case output sits at on 2012+. On my 2014 it appears to actually point up. If that is so, one would have to have a pinion at a slight down angle to put the yokes parallel to one another. As Wayalife just commented, that would be a lot of caster, maybe 7 or 8 degrees. I just wonder if you still could find a better compromise. My front driveline sits at a 6 degree angle. To run a double cardan shaft as suggested, I would need +6 degree pinion angle and 0 caster. Not trying to start an argument at all, I just think we can do better. Maybe I should just solve all problems with a pro rock 44. If JE Reel wants to do a two u-joint rear shaft, I will be their first customer.
Click to expand...

The output shaft angle is pointed upward on all 2012-up and they are all the same. 2007-11 is less due to the 3.8L motor they have. The amount of caster you would have without a double cardan shaft would be up in the +8°. Of course, I run a ProRock 44 on my 2012 and a ProRock 60 on my 2007 and +6° caster is built into them :cool:
 
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