Double Cardan Angle no bueno - JeepForum.com
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post #1 of 62 Old 05-01-2021, 06:05 AM Thread Starter
bruinjeeper
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Double Cardan Angle no bueno

So.

In continuance of my postings in the WDYDTY YJ thread...

I am now running a UCF ultra high clearance skid, which hangs down from the frame rails a LITTLE less than an inch.

At the same time, I installed a SS SYE... moving the rear output snout approximately 3" shorter than the standard SYE I removed.

I had my shaft lengthened to accommodate ...4"... yes... I probably should have gone 4.5-4.75" longer. Either way it works.

What looks no bueno now is the angle at my double cardan joint. I do have a MML of 1".
@fishadventure to retort to your post in the WDYDTY YJ thread, an independent crossmember would exacerbate the issue here. I am wondering why this joint is so tight. While I have you in particular on this thread, I believe you are using an XJ cut down shaft like me which makes your perspective on this situation particularly important.

I believe you are completely flat skid, independent cross member, SS Sye (?) And XJ shaft. If anything, your angle should be worse than mine in THEORY at the double cardan joint.... I'm trying to figure out why it's so steep on my setup.

Also if anyone is running a poly transmission mount, do you know if they are lower profile than stock?

I am not in a position to mod my own OEM mount right now (cut, re-weld). Though I am aware this would alleviate my issue.

Hence, curious on the Poly mounts, if they are in fact lower profile... this would solve this issue albeit leaving me working with a poly mount instead of rubber.

I'm just not understanding why this occurred. I gained MORE in snout shortening than I did drive train lift (3" vs 2.75"). At least that's how I remember the numbers. Why does this angle end up looking so steep?

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~YJOTM MAY '16, JULY '19~


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post #2 of 62 Old 05-01-2021, 06:10 AM Thread Starter
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Upon re analyzing. It looks as though my OEM rubber mount for the transmission is in great shape with a lot of rubber hanging below its steel encasement.... I suppose I could cut down the rubber... maybe trim .5" off it and it would help alleviate my double cardan angle.

But for curiosities sake, it doesn't help me understand why this angle is so steep

~YJOTM MAY '16, JULY '19~


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post #3 of 62 Old 05-01-2021, 06:25 AM
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Did your skid raise your trans height? It seems to me a little would go a long ways.

IIRC Fish runs a very low profile diy solid mount under the trans with bushings mounted at the frame sides. I remember this because I have had the same idea both for serviceability and to raise the skid whilst leaving the trans as close as possible to its original position.

If you cannot fix it with a hammer then it has to be an electrical problem.
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post #4 of 62 Old 05-01-2021, 06:30 AM
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The XJ front shaft mod for a YJ rear has two compromises
One is that you need to make the cut and mate perfect.
Two is that you have to (from the four or five I’ve been able to touch) clearance the outfit with a grinder (mine bound at full droop)
A third is that it’s a little ‘fat’ so with my arrangement I needed to cut out some floor and fabricate a ‘blister-bump’ to give it room to swing (some people beat the floor with a hammer but my way looks oem and was quick and fun to Fab and weld in)
A fourth is the 8.8 flange difference

The ‘89 currently is running a Rugged Ridge rear DC driveshaft because I needed to do the rear joint and balance-ball thingy and I saw an open box deal on Amazon for like $100 and it was a no brainer. It has a visually smaller DC balance joint segment. Not a lot, just somewhat. But I did not have to clearance the joint for binding.

I’m at a stupid angle like 22 or 25; can’t recall. That’s not level, that’s flange to driveshaft

There is a set of extra-clearance parts you can buy from Denny’s? Or Tom Woods? that eliminates the clearance deal.

For you, the solution to the clearance deal? Is to only drive to the mall? Dunno.

I hope this was useful info.

[size=3]Shackles & D-rings are different things.
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post #5 of 62 Old 05-01-2021, 06:35 AM
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Quote:
Originally Posted by Boojo35 View Post
Did your skid raise your trans height?.
I think that is always the case.

Shortening the mount seems a good idea.

A 3/8 plate where the trans mount is supposed to be with tie-fighter wings on both sides welded to tube I think would be heavy enough to eliminate the trans mount/bush the ends while keeping the new skid. That might/should make a few degrees.

[size=3]Shackles & D-rings are different things.
Cranking IS turning over
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post #6 of 62 Old 05-01-2021, 06:37 AM Thread Starter
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So.

Thanks. Lol... I think. It certainly helped me understand the composition of the XJ double cardan joint a bit more.i mean, makes sense, they are front driveshafts from an XJ, angles in that application wouldn't be as intense nor require clearancing as they would in the application we re-purpose it for.

I have plenty of clearance between the tub and the joint. Like stupid amount, unsure how i received that benefit. But am grateful.

Seems as though trimming some of the rubber from the bottom of the OEM mount as much as i can, in combination with grinding out the galleys between the ears on the double cardan unit should clear this issue up. I mean, both those items are free - so they might as well be tries out and see where I sit.

~YJOTM MAY '16, JULY '19~


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post #7 of 62 Old 05-01-2021, 06:38 AM
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Keep balance in mind. Amount removed, not visual symmetry.

[size=3]Shackles & D-rings are different things.
Cranking IS turning over
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post #8 of 62 Old 05-01-2021, 07:02 AM
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What is binding Bruin? Is it just that it looks funky?
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post #9 of 62 Old 05-01-2021, 07:11 AM Thread Starter
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Quote:
Originally Posted by shaggyjim View Post
What is binding Bruin? Is it just that it looks funky?
No binding as it sits or drives on level terrain.

I drove it around my underground and it actually was very smooth.

But it does not take much of an imagination to understand that I have very limited droop tolerance before it will bind... just by looking at it.

Fish brings up a good point in the balance of the shaft. I'll start by trimming the lower section... depending on how much room I have to go... from the OE transmission mount rubber. See how much that alleviates the steepness.

I was more curious as to why this would happen to me with my setup. Fish was enlightening and it makes sense. This is a repurposed front XJ shaft. That said, I found it odd I would end up in this predicament when I have read countless threads where this was not an issue with the mods I did. Quite oddly enough, the issue most folks run into is clearance between the tub and the joint itself. I can fit my entire fist between the two. Insippose the auto tranny assists me in drive train length.

~YJOTM MAY '16, JULY '19~


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post #10 of 62 Old 05-01-2021, 07:16 AM Thread Starter
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Quote:
Originally Posted by Boojo35 View Post
Did your skid raise your trans height? It seems to me a little would go a long ways.

IIRC Fish runs a very low profile diy solid mount under the trans with bushings mounted at the frame sides. I remember this because I have had the same idea both for serviceability and to raise the skid whilst leaving the trans as close as possible to its original position.
Yes. 2.5-2.75".

I just figured doing that while simultaneously shortening the output snout on the tcase 3" would balance and work out.

I suppose aftermarket CV shafts would include a double cardan joint that is both slimmer and "longer" as a unit. Which would solve the issue by providing much healthier tolerance in the case of a steep angle, as in my situation.

This being a front shaft from an XJ, the compromise of getting a dirt cheap (almost free) shaft for repurposement as a rear shaft on our short wheel based YJs is that the double cardan joint was designed as a front shaft unit, where angles are nowhere NEAR as tight.

The thing about an independent crossmember... though it is convenient as heck and in would even agree - proper. Is that in this application, it may reduce clearance for a transmission mount, but because it is mounted up higher on the frame rails, it exacerbates the problem here as the drivetrain is up even higher.

~YJOTM MAY '16, JULY '19~


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post #11 of 62 Old 05-01-2021, 07:18 AM
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Well if you got a few minutes jack it up all the way so the tires are hanging off the ground, put your jack stands under the frame and see if its actually going to bind on you. Do you have an air compressor and speed file?
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post #12 of 62 Old 05-01-2021, 07:22 AM Thread Starter
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Originally Posted by shaggyjim View Post
Well if you got a few minutes jack it up all the way so the tires are hanging off the ground, put your jack stands under the frame and see if its actually going to bind on you. Do you have an air compressor and speed file?
I plan to do that in about an hour.

But as for your inquiry, I JUST received an electrical outlet lol. Air compressor and speed files are probably two years out LOL

What's beautiful about this fishbone rear bumper plate tied into the frame is that it has that glorious tube step. PERFECT highlift jack point DEAD center.
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~YJOTM MAY '16, JULY '19~


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post #13 of 62 Old 05-01-2021, 07:26 AM
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Quote:
Originally Posted by bruinjeeper View Post
Yes. 2.5-2.75".



The thing about an independent crossmember... though it is convenient as heck and in would even agree - proper. Is that in this application, it may reduce clearance for a transmission mount, but because it is mounted up higher on the frame rails, it exacerbates the problem here as the drivetrain is up even higher.
My idea for this is to have a low profile bar that the trans mounts to and at the frame sides it hangs from bobbin style mounts rather than sit on them, so with angles, bends, and some ingenuity you would have all the clearance that is possible. If I do a tummy tuck, it will 99% sure be a home brew.

If you cannot fix it with a hammer then it has to be an electrical problem.
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post #14 of 62 Old 05-01-2021, 07:28 AM
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Ill run mine down in a few minutes so it sets at ride hight. I was looking at mine the other day and it looked close but I'm not getting any binding even at full flex. This has me thinking the cv angles wont change much over the full range of suspension travel. If so and your not binding now you shouldn't bind when your out and about.
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post #15 of 62 Old 05-01-2021, 07:32 AM Thread Starter
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Originally Posted by shaggyjim View Post
Ill run mine down in a few minutes so it sets at ride hight. I was looking at mine the other day and it looked close but I'm not getting any binding even at full flex. This has me thinking the cv angles wont change much over the full range of suspension travel. If so and your not binding now you shouldn't bind when your out and about.[IMG class=inlineimg]/forum/images/JeepForum_2016/smilies/tango_face_grin.png[/IMG]
I dont know man, the dairy queen parking lots around here have some pretty scary curbs and potholes.

~YJOTM MAY '16, JULY '19~


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