Any info or advice on modifying a rear driveshaft double cardan joint for a little more flexibility?

Are you running a special clearanced CV?
I am because originally I had 14" 2.0s in the back and the clearanced cv helped me not need a center limit strap. I've since switched to 12" 2.5s now and I wouldn't need the special cv with those, just already had it.
 
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Not so cut and dry. I run 12's in the back and don't need any of those things. I've got the shortest factory factory drivetrain though with the 32rh and a 231 SS SYE with a flat belly. I burn through driveshafts every year though, probably could be fixed with putting the pinion inline with the drivetrain or dropping the drivetrain a half inch or so
Yours is shorter than mine? My last order was for 17.5". Mine last much longer than a year.
 
I am because originally I had 14" 2.0s in the back and the clearanced cv helped me not need a center limit strap. I've since switched to 12" 2.5s now and I wouldn't need the special cv with those, just already had it.

You also have an 8.8 which has a longer pinion (shorter driveshaft), doesn't it?
 
Yours is shorter than mine? My last order was for 17.5". Mine last much longer than a year.
I forget what transmission you've got, but the 32rh is the shortest factory option. I can measure when I get home, but I think mine is around 22". My operating angle is about 21-22* so they don't last very long, but it doesn't vibe
 
You also have an 8.8 which has a longer pinion (shorter driveshaft), doesn't it?
Not sure on the pinion length, I could try to measure later. Though the offset pinion causes more problem than I think the small difference in length would
 
I forget what transmission you've got, but the 32rh is the shortest factory option. I can measure when I get home, but I think mine is around 22". My operating angle is about 21-22* so they don't last very long, but it doesn't vibe
It's not cut and dried but nothing I have is the same as anything else anyone else has but it's not cut and dried. Got it.

Do a survey Trevor. I'll give you 50 bucks for every TJ rear double cardan driveshaft that is 20" or longer and you give me a dollar for every one shorter than 20". Survey stays open until we get to a 100 respondents. You don't get to respond.
 
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I forget what transmission you've got, but the 32rh is the shortest factory option. I can measure when I get home, but I think mine is around 22". My operating angle is about 21-22* so they don't last very long, but it doesn't vibe
Nv3550, np241, Dana 44 pushed into the gas tank at full shock compression. 4" spring with a Savvy skid.
 
It's not cut and dried but nothing I have is the same as anything else anyone else has but it's not cut and dried. Got it.

Do a survey Trevor. I'll give you 50 bucks for every TJ rear double cardan driveshaft that is 20" or longer and you give me a dollar for every one shorter than 20". Survey stays open until we get to a 100 respondents. You don't get to respond.
Just trying to point out that not every rig that has 12's in the back needs a center strap, a special expensive driveshaft or to be stretched.

Just measured my shaft and it's 20.5" at ride height. So I was a little off, still kinda tempted to take you up on that offer, but idk if anyone around here has a shaft as big as mine...
 
Just trying to point out that not every rig that has 12's in the back needs a center strap, a special expensive driveshaft or to be stretched.

Just measured my shaft and it's 20.5" at ride height. So I was a little off, still kinda tempted to take you up on that offer, but idk if anyone around here has a shaft as big as mine...
I don’t think anyone implied every rig needs those things. Just that the issue exists and those are the typical options to deal with it.
 
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idk if anyone around here has a shaft as big as mine...
There's always a bigger shaft... :giggle:

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Just trying to point out that not every rig that has 12's in the back needs a center strap, a special expensive driveshaft or to be stretched.

Just measured my shaft and it's 20.5" at ride height. So I was a little off, still kinda tempted to take you up on that offer, but idk if anyone around here has a shaft as big as mine...
You may want to check with a few that own non stretched TJ Rubicons before you jump on that offer. They average 17-18".
 
School a newbie here. Single cardan shafts have a longer effective shaft length than DC, and can flex more. Why does everyone use a DC on such a short wheel base?
 
With a DC the pinion has to be in line with the drive shaft. Is the U-Joint angle too steep with single joint?
The rear DC on mine is about 18 deg. A single u joint can't handle that and live long. The two u joints in the double cardan are splitting that angle between the two of them.
 
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It's not cut and dried but nothing I have is the same as anything else anyone else has but it's not cut and dried. Got it.

Do a survey Trevor. I'll give you 50 bucks for every TJ rear double cardan driveshaft that is 20" or longer and you give me a dollar for every one shorter than 20". Survey stays open until we get to a 100 respondents. You don't get to respond.
There it is. I just ordered a rear driveshaft today. A TJ with Savvy UA, 241 transfer case, and Rubicon rear netted a 16" rear driveshaft. Trevor owes you a dollar! ;)
 
UFC ultra high clearance, AX15 trans, np231, AA sye, Ford 8.8.
Driveshaft 17.5"
 
Man, I really feel sorry for all you short shafted guys, I truly wouldn't wish it on anyone.

But it's pretty obvious that you guys are all just jealous of my huge shaft. Is that all you got Tox?
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