Double Cardan setup and a short story - JeepForum.com
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post #1 of 45 Old 05-23-2019, 07:16 PM Thread Starter
MrButterfield
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Double Cardan setup and a short story

This post will be a bit of a confession, followed by a few technical questions. So cozy up, put your reading glasses on if you have to, and enjoy my stupidity. I sure didn't.

I've decided to take the plunge and convert to a double cardan driveshaft due to many drive train failures over the last few years.

This all started when I first got the Jeep onto the road after purchasing it in not running condition. I had a severe vibration under load at a specific speed range. Following a lot of great advice from this site, I found the pinion angles to be incorrect. However, a calculation I never understood or paid attention to was the overall operating angle of the driveshaft.

Some of you may know I towed the Jeep up to Alaska and back last summer. What none of you knew until now was that I suffered two catastrophic drive train failures on that trip. Yeah, I kept it a secret. Mostly because despite being told repeatedly to disconnect the driveshaft when towing for long distances, I never did. The first failure was on the 3rd day of my trip. While being flat towed, the transfer case yoke nut on the Jeep came off, letting loose a 60mph windmill of punches from the driveshaft on all that is holy near the axle. The end result was a destroyed axle pinion, a banana shaped muffler, the muffler heat shield looking like war time aircraft wreckage, and obviously one decimated beyond repair driveshaft. After securing what I could with bungee cords and making it the worlds heaviest Jeep trailer, I carried on to Alaska... 83.9% Jeepless.

Eventually I found a place in Anchorage that could fix my Jeep for me. A new ring and pinion, transfer case yoke, custom built driveshaft, a roll of muffler tape, and $1800 later, I was on my way again. It ran excellent. Way better than before! The Alaska portion of the trip eventually came to an end, making for great Jeep photos, and even greater Jeep memories.

This is the part where Waylon Jennings pipes up, Bo and Luke paused mid air at the apex of their lives, only to deliver a hint of whats terrible to come.

Not 25 miles out of Anchorage headed home, I hear the worst squealing I've ever heard coming from behind the motorhome. Having pulled off the side of the highway, I was unable to spot anything. The Jeep started fine, went into gear, tugged on the motorhome. I figured I picked something up in the RV brakes, but was unable to locate anything. We did what any buddies do when they've been away from home for 5 weeks. We pressed on.

That night, and maybe 100 miles later, we stopped at a campground. There were no pull thrus so the only option was to disconnect and back in. It was then that I realized what pig had been stuck. My transfer case only went into 4L. I smoked the damn transfer case! Like a good boy, I disconnected the driveshaft only after destruction, drank several jack and cokes, and went to bed. I towed my 26.1% of a Jeep home. Once home, a removal and teardown proved to be difficult. Things were so fused together inside the transfer case it wasn't worth the effort.

I found a guy not far from home that specializes in them. He built me a new Dana 20, I installed it, and all was right with the world. Or so I thought. A few local camping trips, hunting season, etc later, I'm already having an issue. 600 towed miles and 150 driven miles, the transfer case output yoke bearing is smoked. So its time.

I spoke with Tom Woods today, what a wonderful company by the way. They spent 40 minutes on the phone with me giving me the ins and outs of driveshafts. I still have a few questions that they were only able to answer "theoretically."

My goal... Ultimate goal. I know the Jeep can be flat towed for long distances without driveshaft removal if its properly set up. Before I resort to removing the shaft entirely, I'll just get a Samurai to tow behind. (I suddenly feel the need to duck)

Question 1: Dana 20 T-case, Centered Dana 44 axle, but its 2" offset to the passenger side. Does anyone have this setup in their CJ5? Im curious about that minor offset and if it affects anything.

Question 2: On the transfer case crossmember/skidplate, I pulled out a stack of homemade? shims. From the factory, were there any shims between the frame and skidplate?

Question 3: Once I go to rotate my pinion up, does anyone have any tricks to knowing about what angle to achieve before futzing around and guessing until you finally get it right?

Question 4: Given that I had nearly 2" of shims between the frame and crossmember, is it possible this angle would cause my transmission (T-18) to leak fluid into my transfer case? Thats also a thing.

Thank you guys for all you do. I'll follow up with photos of the trip, the damage, and where I'm at now.

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post #2 of 45 Old 05-23-2019, 08:07 PM
schardein
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Short answers:
The offset isn't ideal, but probably won't hurt anything.
T18 had factory shims between frame and crossmember.
When using a double carden joint at the transfer case, the yoke on the axle should point straight at the transfer case, or zero angle, in other words. Some might say set it a little lower, so when under power and the pinion tries to come up, it then sits at zero. Either way is probably close enough. They make cheap magnetic angle finders, or use the angle/level function on your smart phone.

Take out your rear driveshaft when flat towing... it's not that hard. You could just undo the rear axle u-joint only and bungee/wire it out of the way, but if you remove it completely, then you can still move the Jeep for short distances with the front driveshaft.
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post #3 of 45 Old 05-23-2019, 08:09 PM
jurgen24
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Technically, to correctly align a double cardan joint the pinion should be aligned and pointing at the transfer case yolk under load (meaning its common to point down a little to compensate). However when the pinion and transfer case are offset then you cant align correctly as it would imply that each end would need to be angled.

In practice, a small offset is probably OK, but it will always vibrate to some extent.

The extra shins were probably there when running a single cardan joint. In that case as long as both yokes are parallel in both vertical and horizontal dimension, then there will be no vibration.




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post #4 of 45 Old 05-23-2019, 09:54 PM Thread Starter
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Quote:
Originally Posted by schardein View Post
Short answers:
The offset isn't ideal, but probably won't hurt anything.
T18 had factory shims between frame and crossmember.
When using a double carden joint at the transfer case, the yoke on the axle should point straight at the transfer case, or zero angle, in other words. Some might say set it a little lower, so when under power and the pinion tries to come up, it then sits at zero. Either way is probably close enough. They make cheap magnetic angle finders, or use the angle/level function on your smart phone.

Take out your rear driveshaft when flat towing... it's not that hard. You could just undo the rear axle u-joint only and bungee/wire it out of the way, but if you remove it completely, then you can still move the Jeep for short distances with the front driveshaft.
What was the thickness of the overall shim(s)?

Also, you're correct. Removing the driveshaft isn't that hard. But highly impractical when you've driven an RV for several hours, wife is hungry, dogs gotta pee, and its pouring outside. It's just not going to happen or the Jeep wont happen. Side point, you cant back up when flat towing. So disconnecting the Jeep in a less than ideal situation isn't just a possibility, its a frequent reality.
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post #5 of 45 Old 05-23-2019, 10:16 PM
RiverandSand
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Having just completed a double cardan driveshft install, yes the Tom Woods folks are awesome. I pitched the pinion up using 6 shims from Rustys Offroad, the skid plate was already dropped 1" so that put the driveshaft at the proper orientation for my setup (CJ 5, 4" lift).
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post #6 of 45 Old 05-23-2019, 11:40 PM
ddawg16
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Why not full floaters in the rear with disconnects?

Questions 1-3....I have a D300.....so I don't have that issue.

#4....Shouldn't both units be sealed? Don't they use different lubs?


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post #7 of 45 Old 05-24-2019, 01:06 AM
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Quote:
Originally Posted by MrButterfield View Post
What was the thickness of the overall shim(s)?

Also, you're correct. Removing the driveshaft isn't that hard. But highly impractical when you've driven an RV for several hours, wife is hungry, dogs gotta pee, and its pouring outside. It's just not going to happen or the Jeep wont happen. Side point, you cant back up when flat towing. So disconnecting the Jeep in a less than ideal situation isn't just a possibility, its a frequent reality.
You can install an electric pump that circulates oil through your tcase how it needs for flat towing with rear drive-line installed. Not a big deal.

As far as running a drive line that's kicked over left or right a little, mine is running at a side shifted angle most people, "that heard from someone", would consider too much. Not a trace of vibration at any speed from zero to 80 mph (so far). Am I potentially wearing out u-joints faster? Yeah. So what? I looove changing u-joints. I live to change u-joints, so I'm as happy as a pig in slop about that. From the manufacturer many vehicles were sold this way. Not a big deal.

OP, definitely learn how to set up proper drive line angles, so there's not a repeat of the banana shaped muffler. Wife and dogs ain't gonna stick by ya for round two. Or better yet, hire a professional to finish this. DS spins at upwards of 6,000 rpms. No room for error here, as you well know. Just by reading your post above I know you are not ready for this on your own. Not without plenty more google searches anyhow. Nothing in this thread has fully prepared you for success.

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post #8 of 45 Old 05-24-2019, 07:30 AM
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Herm the overdrive guy is who Id call about the full floater rear set up. Then all you do is lock or unlock the hub in the rear.
http://hermtheoverdriveguy.com/

Good Luck! Shawn
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post #9 of 45 Old 05-24-2019, 08:40 AM
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I too have a double cardan Tom Woods rear driveshaft in my SOA CJ5...the DS is only about 14 inches long and runs at a 35 degree angle, smooth as can be.

Be sure to figure in the length of the double cardan joint when calculating your pinion angle.
A little more work, but you should remove your rear spring perches and leave the new ones loosely fit before welding them in place. You'll be able to precisely fine tune the pinion angle that way.
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post #10 of 45 Old 05-24-2019, 10:25 AM
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Warn was the only company I ever heard of that made a full floater kit for a CJ rear axle. Warn hasn't made a full floater kit for a CJ in well over a decade, almost two, so lets stop suggesting that for the OP. Unless he wants to find a clapped out used set on flea bay. As far as figuring out what shims to use, an angle finder is your friend here. All checks to be done with full weight of CJ on the axle in a going down the road configuration. Ignore that last sentence and you'll regret it. Use the angle finder to determine where the axle pinion angle currently is. Then use the angle finder and string stretched taunt from the tcase output (factoring in length of CV joint) to the hypothetical fulcrum point center-line of the axle pinion gear to determine angular difference. Yes, easier said than done, but really no big deal. Use your creativity, or better yet, hire a professional. This board recommends hire a professional for far less important jobs, so I'm baffled at the lack of concern here. Anyone who's ever seen a driveshaft fly out of a vehicle knows they can easily kill.
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post #11 of 45 Old 05-24-2019, 11:23 AM
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I mentioned using an electric pump many years ago and never got any feedback on it. A couple months back I mentioned it again and there was some discussion but no one that really knew how to do it and where to put the port to oil the rear bearing of the Dana 300. I have never seen the pump mentioned before I originally mand the inquirey. What kind of pump whould one use? I have a pre-oiler pump for my 383 Chevy in my 1956 GMC that I put in there in 1991. It pumps 20W50 oil fine but that is not gear oil. I think if someone would figure out the correct pump and where to drill and tap the tail housing, this would be a great conversion. One could trigger the pump with the trailer brake lights and have it run for a few seconds or just run on a timer every so many minutes.

I believe Warn stopped making the hub conversion due to failures. Hubs are weak compared to drive flanges. Some guys free float the rear end and then pull the axels when they want to tow and cap the axels with dummy slugs. It is probably more work than pulling the drive line, but you do not have to get down in the mud to do it and you can make quick work out of it with an impact gun.

As said above, "Herm the overdrive guy is who I’d call about the full floater rear set up." I believe he purchased the patent from Warn to do the conversion.

Quote:
Originally Posted by TIPPEDITOVER View Post
You can install an electric pump that circulates oil through your tcase how it needs for flat towing with rear drive-line installed. Not a big deal.

As far as running a drive line that's kicked over left or right a little, mine is running at a side shifted angle most people, "that heard from someone", would consider too much. Not a trace of vibration at any speed from zero to 80 mph (so far). Am I potentially wearing out u-joints faster? Yeah. So what? I looove changing u-joints. I live to change u-joints, so I'm as happy as a pig in slop about that. From the manufacturer many vehicles were sold this way. Not a big deal.

OP, definitely learn how to set up proper drive line angles, so there's not a repeat of the banana shaped muffler. Wife and dogs ain't gonna stick by ya for round two. Or better yet, hire a professional to finish this. DS spins at upwards of 6,000 rpms. No room for error here, as you well know. Just by reading your post above I know you are not ready for this on your own. Not without plenty more google searches anyhow. Nothing in this thread has fully prepared you for success.
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post #12 of 45 Old 05-24-2019, 11:44 AM
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Seeing as the OP has a Dana 44 rear, there are other ways to do a full float. You can have an adapter ring machined to use a small bearing Chevy Dana 44 front spindle and index it into and bolt up to the factory bearing cup/flange and use Ford internal spline hubs and have Branik/Dutchman/Moser cut custom length double spline axle shafts and use the stronger internal spline hubs or drive pucks if needed. You get the plus of converting to rear disc brakes with the Chevy 6 bolt front caliper bracket. A friend did this setup on an early offset dana 44 and is running it on 36" Iroks powered by a 350SBC.

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post #13 of 45 Old 05-24-2019, 01:12 PM
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Quote:
Originally Posted by TIPPEDITOVER View Post
.... DS spins at upwards of 6,000 rpms. No room for error here, as you well know. Just by reading your post above I know you are not ready for this on your own. Not without plenty more google searches anyhow. Nothing in this thread has fully prepared you for success.
Hmm.
6,000 RPM for a Drive shaft? with 4.1 gears and 33" tires that would be roughly 147 MPH


There is still the driveshaft quick disconnect. Just pull a lever and disconnect your rear driveshaft.


https://www.remcodsc.com/coupling/

Buy the end piece and send it to Tom Woods and I'm sure he would install it on his DS with a DC on the other end.

Besides You could still drive the jeep on the front axle with the read disconnected. Would work even better is he twin sticked it.
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post #14 of 45 Old 05-24-2019, 03:49 PM Thread Starter
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I suppose I should clarify a bit about the shims. By shims, I do not mean the axle shims. I'm referring to shims that go between the transfer case skid plate/cross member and the frame.

As for setting up the driveshaft angle, I think I do actually have a handle on it. While I'm in no way a professional, a ton of internet research and a lengthy phone call with Tom Wood's tech team gave me the confidence to set the angles properly for a double cardan shaft. I have now done so and will be verifying my measurements and angles with them on Tuesday when I order the shaft.

As for the full floater with hubs, I did look into that and I cannot find anything for my differential that isn't used or sketchy. While I think it might work for me as I don't do much more than light trails (mostly during hunting season), I'm a bit scared of avoiding one failure point by adding what seems to be another.

So the offset in my D44 is 2" towards the passenger side from center. I dont believe this is an actual offset D44 rear. The pumpkin is centered, but as someone mentioned before, possibly in another post, because the differential housing and ring gear are centered, the pinion is offset by a small amount. This will be a measurement I give to TWDS on Tuesday.

I think the Dana 20 transfer case is fine to flat tow for extended range. The guy that built it said he's flat towed several of them for many miles and has never had a failure such as mine. He felt that the vibration coming from the driveshaft was more of the culprit and that fixing that would prevent future failures. I do like the oil pump idea though. I believe its the Dana 300 that can't be flat towed for an extended range?

@John Strenk - That looks nifty! I did watch the whole install video of that disconnect. They never really showed how stout the splines are on the engagement coupler. Any thoughts on something like that under the jeep during hunting season? I wonder if mud or other debris would interfere with operation of that slide collar. Definitely worth considering! I think in this instance, I would probably just install the new drive shaft, run it for a few hundred miles to verify it was a solution, then have it modified with a disconnect.


So still wondering about the oil leaking from the T-18 into the Dana 20 as well as the shims for the transfer case skid plate.
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post #15 of 45 Old 05-24-2019, 05:53 PM
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Quote:
Originally Posted by TIPPEDITOVER View Post
You can install an electric pump that circulates oil through your tcase how it needs for flat towing with rear drive-line installed. Not a big deal.

As far as running a drive line that's kicked over left or right a little, mine is running at a side shifted angle most people, "that heard from someone", would consider too much. Not a trace of vibration at any speed from zero to 80 mph (so far). Am I potentially wearing out u-joints faster? Yeah. So what? I looove changing u-joints. I live to change u-joints, so I'm as happy as a pig in slop about that. From the manufacturer many vehicles were sold this way. Not a big deal.

OP, definitely learn how to set up proper drive line angles, so there's not a repeat of the banana shaped muffler. Wife and dogs ain't gonna stick by ya for round two. Or better yet, hire a professional to finish this. DS spins at upwards of 6,000 rpms. No room for error here, as you well know. Just by reading your post above I know you are not ready for this on your own. Not without plenty more google searches anyhow. Nothing in this thread has fully prepared you for success.
My narrowed 14 bolt puts my pinion kicked over 4" from the output. That puts me at 15* up on the driveshaft, and 6* of side offset over a 27.5" double cardan driveshaft.
I initially was worried about the offset to the side being a issue when I was chasing down a vibration problem. Until I saw a TJ with a 8.8" swapped in it. Very common swap, and that pinion is offset more than mine is.

No vibration issues with mine once I built a new one.Works well at 55-60 mph cruising speed.
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