Bad Vibration after Front Driveshaft Install

[ShadowsPapa]

Yeah unfortunately for me I am beginning to see this now. Oh well, this is certainly not the first time I've made a purchase of a product that has left me somewhat disappointed. Stronger? Well I really don't know but I can say for sure it's alot bigger and heavier.

People with this issue are out there, but even those with the problem are somewhat likely to ignore it or get by with it rather than talk about an $800 shaft being less than ideal for their use.

anyone with a SelecTrac system might want to double-think things as it means it won't always be fun and smooth if you drive with it in 4HA in rain and snow and sometimes dry roads at normal road speeds.
But those people are less likely to be the hard-core rock climbers who don't give a rip about road manners as long as it climbs boulders and goes through deep ravines without pause.

I've run across this bit at least 4 times just in these forums, not counting over the years in other places so no one can say it doesn't exist or it's not a thing.

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[Wheelin98TJ]

Fine for factory caster, factory height and not driving over 20 or so in 4 wheel drive.

In each case I've helped, the solution was to line the pinion up with the drive shaft. A couple were rear shafts with pretty decent lifts, others were front.
If you notice, even the vendor said they were doing the same thing - changing pinion angle to match the drive shaft.
One I worked with for the rear shaft vibration is a forum member. Otherwise, it's been others.
So you either line up the pinion - get rid of some caster, or you use a different shaft.
Note that the factory shaft has a CV joint at the transfer case due to the canting of the front t-case output putting a greater angle on the joint. A cardan joint would not cut it on the rear of the front driveshaft even from the factory because of the angle.
The front end of the factory shaft is a single cardan joint - running very nearly straight at stock height and stock caster.
A 2" lift isn't going to change that angle a whole lot - still inside the range of angles where the vibration will be minimal or not noticed.
But when you add caster and a higher lift, now you put that single joint at such an angle at speeds above a certain point, it's going to be a bad vibration.

doesn't matter what others came with from the factory because those were running minimal angles from the factory and likely not seeing high speeds in 4 wheel drive.
The effect is greater with greater angle and greater speed.

The OP is not the first person I've talked about this issue with, not the first person I have helped or tried to help - and again, notice that even the VENDOR! is saying "get rid of some caster (meaning they are telling him to reduce that angle)

I've been through this sort of thing several times over the years, and again, even with a forum member who ended up tilting the pinion to match the shaft. Vibration gone.
It doesn't matter a lick if it's a front shaft or rear shaft, the only difference is that with a front shaft, many people are getting by or putting up with it because it's only a bother in 4 wheel drive and at some speeds, probably over 20 mph, because it's shaft RPM that amplifies it into a vibration.
geometry, science.

Jeep did what they did because they could.
As far as that goes - most vendors sell front drive shafts for lifted JKs with a CV front joint.
I wonder why.........

I used my 4” lifted TJ as a daily driver for many years. I once drove it home several hours from the sand dunes on the front driveshaft cause I broke the rear. Zero vibrations ever. Drove 80 mph down the highway in 4wd if you wanted to.

I’ve been a member of JeepForum.com for 20 years. The topic of using double cardan joints on both ends has came up maybe 3 times. And I don’t recall it ever being the solution.

Can you provide any examples of a Jeep needing and using a double cardan on both ends? Any link from any forum will work.

 

[WILDHOBO]

So in other words, their shafts force you to do things that may not work for steering and suspension just because they are making a killing on so-called "performance shafts".

4 degrees is not even in the factory specs for caster.
Hacks.

These are mine. The jointed one with cv at the t case and 1350 at the cv is my Dana spicer performance rear, rated for stock to a 6” lift. It’s been amazing, and yes, my rear pinion is adjusted to around 1 degree.

The front double cardan 1350 was made locally by a driveline shop for $400. I have yet to install it. I’ve had it since last August. Oops. I do expect to need to adjust the front pinion to a compromise angle, getting the best caster/pinion angle combination. If it doesn’t handle well at high speeds, it’ll get pulled. I admit, I very much like my stock front shaft from a smooth operation standpoint. I have 4hi auto, so my front driveshaft sometimes rotates at 65-70mph. It needs to be smooth. I’ll take smooth over strong in the front.

 

[ShadowsPapa]

I used my 4” lifted TJ as a daily driver for many years. I once drove it home several hours from the sand dunes on the front driveshaft cause I broke the rear. Zero vibrations ever. Drove 80 mph down the highway in 4wd if you wanted to.

I’ve been a member of JeepForum.com for 20 years. The topic of using double cardan joints on both ends has came up maybe 3 times. And I don’t recall it ever being the solution.

Can you provide any examples of a Jeep needing and using a double cardan on both ends? Any link from any forum will work.

So you are saying all of the videos, all of the math and science is wrong.
That anyone can indeed run a single joint at more than a few degrees and it won't vibrate.

What was the angle on your TJ's pinion end joint?
How much caster did you run and what was the angle of that joint,
and was it a single joint at both ends or a double at the transfer case and a single up front?
If your pinion angle was low and there was little angle to the joint, then you got by.

If it was a single joint at both ends - that matters, because one can cancel out the other.
So we need to go tell all of those people, including spicer, their videos are crap and dead wrong, it won't matter, you won't have vibration.

And yet in this very thread, two are having vibrations - since using these shafts.

 

[ShadowsPapa]

These are mine. The jointed one with cv at the t case and 1350 at the cv is my Dana spicer performance rear, rated for stock to a 6” lift. It’s been amazing, and yes, my rear pinion is adjusted to around 1 degree.

The front double cardan 1350 was made locally by a driveline shop for $400. I have yet to install it. I’ve had it since last August. Oops. I do expect to need to adjust the front pinion to a compromise angle, getting the best caster/pinion angle combination. If it doesn’t handle well at high speeds, it’ll get pulled. I admit, I very much like my stock front shaft from a smooth operation standpoint. I have 4hi auto, so my front driveshaft sometimes rotates at 65-70mph. It needs to be smooth. I’ll take smooth over strong in the front.

How much of an angle that front joint is subjected to or rather put into matters. It's going to take some angle just fine - the more angle, the more RPM DIFFERENCE there is between the speed change cycles. At just a small angle, the RPM changes (two for every revolution) will be smaller. At larger angles, the RPM changes will be more drastic, as seen in the videos you can actually see it with the tape stripes on the sprockets - the shaft appears to almost stop, them move again, and it does that two times for each revolution. So the faster it runs, the more it's going to tend to vibrate, and the more severe the angle, the more likely it is to make you feel it.
A lot of other things may come into play - suspension tightness, for example.
But right here, two people have some out and said "I have a vibration".
the solution - give up some caster, reduce that angle.
It's not that hard - it's geometry, science.
We also know Jeep people don't like to talk about how a change they love and need might be less than ideal in other circumstances, there's some psychology to this as well.
But to say after all of these videos out there, from all sorts of people, Spicer, other driveline makers and techs, showing how it all works, to say "it can't be a problem" or "isn't a problem"- it must be a problem for people to keep making videos year after year, dozens of them.

Again, it goes back to what's the primary purpose or need, what will a person deal with to accomplish a goal. And, there's size, speed, and angle variables, among others. A larger joint isn't quite as prone, but then look at the jerking happening on front axles on a tight turn. There are videos out there showing that it's due to the u-joint angle!

if you have enough angle on a single cardan joint, it's very possible, even likely, it's going to vibrate at speed. Note I said "enough angle" - I didn't say "just any angle".

 

[WILDHOBO]

Here is Spicer’s page showing all their performance JT drive shafts. I find it interesting that their fronts are built exactly like others. Single on pinion end, double at the t case.

https://spicerparts.com/parts/drive...performance-driveshafts-for-jeep-gladiator-jt

 

[WILDHOBO]

People with this issue are out there, but even those with the problem are somewhat likely to ignore it or get by with it rather than talk about an $800 shaft being less than ideal for their use.

anyone with a SelecTrac system might want to double-think things as it means it won't always be fun and smooth if you drive with it in 4HA in rain and snow and sometimes dry roads at normal road speeds.
But those people are less likely to be the hard-core rock climbers who don't give a rip about road manners as long as it climbs boulders and goes through deep ravines without pause.

I've run across this bit at least 4 times just in these forums, not counting over the years in other places so no one can say it doesn't exist or it's not a thing.

I’m a hard core rock crawler, who has 4 hi auto. I guess I’m proof that we exist. . I’m definitely thinking it through. That’s the reason my new traditional double cardan front shaft has not been installed yet. I may just keep running my oem front until it fails, keeping this one as a cheap spare. Not meaning cheaply built. Just no Adam’s sticker to double the price.

 

[ShadowsPapa]

Here is Spicer’s page showing all their performance JT drive shafts. I find it interesting that their fronts are built exactly like others. Single on pinion end, double at the t case.

https://spicerparts.com/parts/drive...performance-driveshafts-for-jeep-gladiator-jt

Double on the transfer case end (or even using a CV at that end) is necessary because of the upward tilt of the front output of the transfer case putting that joint area at a fairly extreme angle..
The stock JT sees almost no angle at the front joint - the shaft and pinion are fairly well lined up so a single joint works perfectly well there from the factory with stock caster and height.

The issue MAY present itself - not a given, but possible - when the caster is increased, tilting the pinion downward combined with a high lift, taking that shaft higher up, the two changes combining to put that front single joint into iffy territory. might work - might vibrate, depending on lift, caster (angle of pinion) size of the joint used............
Also, as a rule of thumb, if you double the operating angle you cut the lifespan of the U-joint in half.
This is from MotorTrend -

 

[ShadowsPapa]

I’m a hard core rock crawler, who has 4 hi auto. I guess I’m proof that we exist. . I’m definitely thinking it through. That’s the reason my new traditional double cardan front shaft has not been installed yet. I may just keep running my or front until it fails, keeping this one as a cheap spare. Not meaning cheaply built. Just no Adam’s sticker to double the price.

I think I mentioned before - I can go to a local performance shop and have a driveshaft built to those, or even better specs, for less money.
They built the rear driveshaft for my Eagle. (the car is short, both driveshafts pretty darned short and the thing is prone to vibration if things aren't just right - I even had to use shims to get the pinion angle right to smooth things out on the highway.

 

[WILDHOBO]

I for one will sacrifice a bit of caster in order to drive smoothly at 70mph. I’d never exceed that in 4hi auto. There’s no common sense reason to. If it’s slippery enough to use 4 hi auto at all, I’m probably not exceeding 65. I don’t leave mine engaged. If it dries out, I drop down to 45mph for a second and put it back in 2hi.

 

[JeepOfTheseus]

Another fellow here had the same sort of driveshaft for his REAR shaft. It was also a single joint at the pinion or axle end. He ended up having the change the pinion angle to make that joint run at about 1 degree or less. And if I recall, the company he got the shaft from agreed.
(not a pun, not intentional, but I had to laugh after I read that sentence)

That was probably me, and I haven't completely resolved the issue yet. I recently noticed some dry black grease/crud under the diff/yoke opening and I suspect I botched the pinion preload. I'm taking it to a shop next week.

In the meantime, I finally got some angled/wedge spring pads for the rear, which will let me correct the pinion angle without having the angles bowed like crazy.

Once I have the shop look at the diff and I get the pinion closer to 0*, I'll update whether it resolves my vibration issues.

Funny thing is, the front is at 7-9* (I'm running Adams front and rear), and that didn't introduce issues (even though I removed the FAD).

 

[JTenn]

I’m a hard core rock crawler, who has 4 hi auto. I guess I’m proof that we exist. . I’m definitely thinking it through. That’s the reason my new traditional double cardan front shaft has not been installed yet. I may just keep running my oem front until it fails, keeping this one as a cheap spare. Not meaning cheaply built. Just no Adam’s sticker to double the price.

But that Adam's sticker is REALLY COOL!! Lol ? Oh, then there was also the free t-shirt!!

 

[JeepOfTheseus]

But that Adam's sticker is REALLY COOL!! Lol ? Oh, then there was also the free t-shirt!!

 

[ShadowsPapa]

In the meantime, I finally got some angled/wedge spring pads for the rear, which will let me correct the pinion angle without having the angles bowed like crazy.

Hoping for the best of luck and all things work out.

That's the other thing about a lift above a certain height, and tilting the rear axle housing to achieve a straight line on that rear joint - spring bow. Sounds like you have it planned and under control so far.

 

[Gizmo]

Other than my jk and my jt all my straight axle 4x4s have had a single at the axle end of the shaft and a double on the transfer case from OE to Tom Wood shafts and any other aftermarket shaft I have owned . It works on TJs and should be fine on JL/JTs with pinion angle at 0 degrees which makes caster about 6 degrees . Mines been at 6 degrees without a vibe since last summer. Usually ran about 5.5 degrees on the TJ with about 3-4" lift . Never had a need for a DC on each end yet and thats about 2 dozen 4x4s to date . Im betting OP has something else going on . Maybe a joint out of phase ?

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