Help me diagnose a driveline vibration - Slinky 3" lift (2 Viewers)

[digitalmarker]

Hey guys, need help chasing a driveline vibration and wanted to get some opinions and experiences from you guys to see if there is anything I missed.

I recently upgraded to the 3" Slinky Stage 1 kit which ended up at about 4" of height increase, re-geared to 488s, new axles, Delta 4" radius arms, and freshly serviced the front knuckles. I was already using a double cardan drive shaft (was running a 4" slee lift before that). Truck feels really good besides for a vibration that is felt under acceleration between 35-45 mph.

After some tweaking with the adjustable UCAs and Landtank's LCAs I got the rear TC vs pinion angles are matched within 1*. The front pinion angle at the diff is 7.5*, and the angle of the DS is 10.5*, netting out a difference of approx 3*. Not a desired 1* difference, but not terrible either.

The vibration goes away when I lock the CDL and remove the front drive shaft entirely. I had the Slee DC shaft rebalanced (twice) by a reputable and well-known local shop, which surprisingly made the vibration significantly worse. I also tried a Landtank DC drive shaft from my buddy's truck with a similar result - just slightly less vibes than the Slee. What's nuts is that he's running the exact same setup as me in terms of height, lift, gears, etc., and has no vibrations in any range.

The driveline shop recommended doing a double cardan DS with spicer joints, so basically a double joint at each end. I installed it last week and while the vibration reduced significantly, it still vibrates and drives me nuts.

I am planning to go part time at some point, but spend a lot of time driving in the snow in the exact range where I am getting vibrations now and want this fixed the right way.

Before you refer me to the search function, trust that I read and re-read every post I could find on the subject.

At this point looking for input on what I could have missed and where I could look next? Folks who are running the same lift height - are you experiencing something similar?

Any thoughts and ideas are much appreciated. Thanks in advance!

 

[mikedamageinc]

You didn't mention tires, what type & size?
Have they been balanced recently?
Do they have uneven wear?
Try rotating them or swapping sets with your buddy to test?

 

[Shoredreamer]

You didn't mention tires, what type & size?
Have they been balanced recently?
Do they have uneven wear?
Try rotating them or swapping sets with your buddy to test?

Second that. I have the same height lift, same caster and DC and was chasing a similar vibe. I got new tires and now smooth as butter.

 

[BILT4ME]

The DC end is supposed to at the transfer case, not the differential.

The pinion needs to point at the transfer case if possible so that end is straight. It's different than a standard u-joint.



Wait, you have a double-double cardan shaft? Not seen that before.

 

[Heckraiser]

That is a double double cardan? I've never seen that.

Don't rule out the possibility that the vibe could be coming from your rear driveshaft too. I was convinced my noise was coming from the front end--even went away when I pulled the front shaft. I know it makes no sense, but after much more testing and diagnosis, I believe it is actually the rear slip yoke. Will verify this week most likely.

 

[digitalmarker]

The vibrating goes away entirely when I pull the front drive shaft.

The tires are 35” Toyo OpenCountry MTs on stock tires.

I only developed the vibes after changing the ride height with the slinky kit (and other mods I listed). I drove about 2000 miles on those tires and didn’t have vibe issues.

Is it common to have tire vibrations at 30-45mph? Everything I’ve read says that this speed range is almost always drivetrain related.

 

[desmocruiser]

It sounds like you addressed the most common culprit, the front drive shaft that is typically eliminated with a DC shaft.

However, there is a possibility that the rear DS is causing what you are feeling

I chased a similar issue several years ago with a Slee 4” lift and finally brought both my drive shafts (Front DC and stock rear) to a very reputable driveline shop and had both phased and balanced and it disappeared.

You can search (yes I hate it when people tell me this) and there are probably the threads that put me in this direction.

Also, can you remove the rear DS (since you have the 7 pin mod and center diff switch) and drive to see if there is a difference, same as you tested the front Or swap your buddy’s Rear DS and even wheels/tires to further track down the source of the issue.

Any idea what the caster reading was before the new lift and after?

Good luck, I fought this for some time and agree, it can be very annoying.

 

[Heckraiser]

The vibrating goes away entirely when I pull the front drive shaft.

The tires are 35” Toyo OpenCountry MTs on stock tires.

I only developed the vibes after changing the ride height with the slinky kit (and other mods I listed). I drove about 2000 miles on those tires and didn’t have vibe issues.

Is it common to have tire vibrations at 30-45mph? Everything I’ve read says that this speed range is almost always drivetrain related.

Yeah, that's kind of what I was getting at. My noise (not really a vibe, in my case) came after a change in lift height. I was certain it was the front since that's typical and to my ears, it sounded like it was emanating from the front. Pulled the front shaft and it went away, which seemingly confirmed my suspicion that it was the front. That was enough evidence for me to go out and buy a DC shaft. But when installed, the noise persisted. I guess what I'm saying is removing the front shaft and the noise going away can be a false positive for diagnosis purposes. In my case the culprit was the rear, despite the test and MUD research.

Could also be as simple as rear u-joints. They don't like a sudden change in driveshaft angle if they've been sitting in a certain position for many years.

 

[baldilocks]

You have figured out that the vibration is in the front driveline, but why?
Two things, the rotational speed of the driveline has increased due to the 4.88’s and the Delta arms put your castor angle where it should be and now the pinion is too far down and out of proper alignment with the angle of the driveline.

If you were running Slee castor plates before (like I used to) then your castor was at minimum spec or even less (like mine was) but the DC shaft was happy.

You can either get a lower lift spring or go part time now or drive around with the CDL locked and front driveline removed.

Going from castor deficient plates to Delta arms has moved your happiness from one area to another. It’s a vicious cycle man and you are definitely caught up in it.

 

[tacocat]

Double-doubles are typically seen in really high lifted SWB rigs or old school monster trucks.

@digitalmarker . I have a similar issue with a slight oscillating grrrr noise that occurs between 65-75. I'm running Dobinson Variable Rate Taper Springs with @landtank 2.5 caster plates, so we aren't too far off. I've been emailing good old @NLXTACY about it the last two days, and I need to do so more diagnosing.

Your drive line angles look acceptable for a single DC. A double seems extreme, but who knows. A few questions...

You went from a Slee 4" lift to a 3" Slinky, but are reporting a 4" change in height (it doesn't look like it in the pics)?

Is your vibration felt or heard? Is it loud or quiet?

Does it occur when applying gas, and go away when you left off the gas?

Are you running an adjustable front track bar? This isn't supposed to affect driveshaft function, but its food for thought.

Everyone else has had good suggestions and comments.

 

[bajaphile]

Did you do all this work at the exact same time (lift and gears)? Generally when you experience a vibration under acceleration only, that points more towards a pinion/differential issue, unfortunately. Who did the gears? You might want to bring it back to them and see if they can fix it. Sounds like you've exhausted the driveshaft arena.

 

[digitalmarker]

Thanks for the comments and the thoughts. Some things I should have mentioned earlier to answer follow up questions:

The rear driveshaft has been balanced and serviced with brand new Toyota U-joints. The rear vibrated quite a bit too when I first did the lift, but I was able to dial it in with adjustable UCAs I already had, and the Landtank LCAs I got from Wits End. The pinion angles on the TC and the diff are now within .5* of each other, and without a front drive shaft the rear feels perfectly fine.

I was running Slee arms before, and my caster reading was actually far above the recommended range (5.7* on both wheels). The Slee arms are designed for 4" and 6" lifts from Slee. The 4" Slee lift I had before was more like 5", and the Slee caster arms had my caster within range, albeit at the top of range. Once I went to a lower height lift with Slinky (netting out 4" of total height), the Slee arms overcorrected caster which lowered the front pinion angle even more out of range. Specifically, with Slee arms the difference between the front DS angle (11*) minus the front pinion angle (3*) was 8* - far above the recommended 1*. I don't know what caster angle I am at now - getting another alignment next week - but the angle difference between the DS and the pinion flange is now around 3*.

I ran a single CV double cardan shaft from Slee ever since I lifted the truck. It worked fine with the Slee kit and Slee arms, but started causing vibration once I went down in height with the Slinky springs. The vibration persisted when I swapped over to the Delta arms.

With the new double-double DC shaft I am running now, the vibration is reduced, but still still persistent between 30-45mph, most pronounced between 40 and 45. I feel it through the cabin/in the seats and it resonates through to the steering wheel.

I am running an adjustable panhard bar in the front. It is tightened at the adjustment nut, and torqued in both locations at the frame/axle. The axle itself is perfectly centered under the vehicle.

The vibration is related directly to acceleration - I feel it more when I am down on the gas pedal, and reduced if I go lighter on the gas pedal. Taking my foot off the gas makes it go away completely.

 

[digitalmarker]

Did you do all this work at the exact same time (lift and gears)? Generally when you experience a vibration under acceleration only, that points more towards a pinion/differential issue, unfortunately. Who did the gears? You might want to bring it back to them and see if they can fix it. Sounds like you've exhausted the driveshaft arena.

I got the gears done by Ken Francisco at gearinstalls.com. He is a reputable vendor on here, and was super meticulous with the project - literally texted me a picture of every step. The diff is perfectly quiet and smooth, I can move the pinion flange to turn both wheels with tires on them when the front is lifted up.

Is there a way to test for this without taking the diff out of the axle?

 

[tacocat]

I forgot to mention, that's one seriously clean undercarriage. What generation of Slee Caster Arms were you running prior?

Is the driveshaft properly lubed? Perhaps the driveshaft is transmitting force to something causing the harmonic imbalance. This is interesting because you have addressed all the usual suspects.

I take it the pic of the transfer case was flange was prior to properly torquing it down. Perhaps you should double check the torque of the hub nuts and steering knuckle nuts.

 

[BILT4ME]

Just spitballing here.

Factory front DS is supposed to be 90° out of phase.

Should your double-double be out of phase as well? Try it and see?

 

[landtank]

Double-doubles are typically seen in really high lifted SWB rigs or old school monster trucks.

@digitalmarker . I have a similar issue with a slight oscillating grrrr noise that occurs between 65-75. I'm running Dobinson Variable Rate Taper Springs with @landtank 2.5 caster plates, so we aren't too far off. I've been emailing good old @NLXTACY about it the last two days, and I need to do so more diagnosing.

Your drive line angles look acceptable for a single DC. A double seems extreme, but who knows. A few questions...

You went from a Slee 4" lift to a 3" Slinky, but are reporting a 4" change in height (it doesn't look like it in the pics)?

Is your vibration felt or heard? Is it loud or quiet?

Does it occur when applying gas, and go away when you left off the gas?

Are you running an adjustable front track bar? This isn't supposed to affect driveshaft function, but its food for thought.

Everyone else has had good suggestions and comments.

What is the measurement from the center of the front hub to the underside of the fender? My 2.5" plates are expected to not vibrate with the stock shaft for lifts in the 2-3" range. And that is actual lift not what's on the manufacturer's label.

 

[tacocat]

What is the measurement from the center of the front hub to the underside of the fender? My 2.5" plates are expected to not vibrate with the stock shaft for lifts in the 2-3" range. And that is actual lift not what's on the manufacturer's label.

I’ll get measurements this weekend when it’s isn’t one million degrees in the garage.

 

[azngarage]

From the photos, i see that the nuts and bolts for the driveshaft is still loose.

 

[landtank]

From the photos, i see that the nuts and bolts for the driveshaft is still loose.

Holy crap. There is a gap between the diffs companion flange and the drive shafts yoke. That thing is on its way to falling off

 

[digitalmarker]

Holy crap. There is a gap between the diffs companion flange and the drive shafts yoke. That thing is on its way to falling off

I took the photos before tightening everything down. Everything is tight and torqued to spec. The photos were intended to show the double-double CV joint. I was going to take a pic of it on the ground but was too excited to put it on and drive vibration free. Wish it was loose because that would be an easy solve!

@BILT4ME I tried running the single-CV DC shaft in and out of phase, with the exact same result. I have not tried it on the double-double one, but will try it this weekend. The owner of the shop that built the double-double shaft for me didn't think it would make a difference. He also suggested building this double-double shaft after he tried re-balancing the single CV shaft I already had several times, and after I tried running my buddy's Landtank DC shaft, which is running smoothly on his truck. At this point I am 99% sure the front DS itself is not the problem, which is why I am looking for other areas to inspect where I may have not looked yet.

@tacocat the way I measured final lift height is by measuring from top of the flare to the center of the wheel/hub, which nets out 24" all around. Comparing to the 20" stock height, it nets out to 4" actual lift. I am not running spacers. This measurement method is what I found on here in other threads.

The hub nuts, steering components, etc., are tightened to spec. I am not feeling any loose bearings or hubs or steering when I do the 6-12 or 9-3 tests on either wheel.

This weekend I am going to try the following:

• run the truck with the rear drive shaft out, front shaft only
• turn the double-double shaft out of phase, and run it without the rear shaft
• run the truck with the tires/wheels off my Tundra to eliminate tire related issues or wheel balance issues
• drive around with a go pro mounted under the truck pointing at the TC and pinion side of the driveshaft

Obviously I am grasping at straws here as all of these have been all but ruled out as culprits, but I don't have any other things to try at this point. Recording under the truck with a go pro is a long shot too because it's hard to see/capture anything unless something is obviously loose and flopping around, which I doubt it is otherwise it would be happening throughout the speed range, not just 35-45mph.

Any other ideas are welcome - please share.