Drive Shaft Vibrations

[Hunyuk]

Just wrapped up installing my Slee 6" lift. I've yet to install my sliders and armor, and it will be a while before I do bumpers. All told, I'm probably sitting at more like 7" of lift right now. At 35mph+ when I decelerate, I get a nice "grrrrrrrrrr" vibration from the drive train. I have a brand new double cardan front, and the stock rear. Visual inspection clearly shows that the angle on the rear is much more dramatic than the front. After talking with Slee, it seems likely that my rear pinion angle is causing this.

It has been suggested to put some weight (sand bags, or similar) in the back and to shorten (although I think I actually need to lengthen) the rear upper control arms to temporarily reduce the angle. I'm posting here looking for suggestions, and have a few questions too.

1. Should I be concerned about damaging my rear drive shaft operating the vehicle like this for a few months?
2. Any other suggestions with respect to correcting the angle?
3. Is anyone running a double double cardan rear drive shaft? Thoughts? (it was suggested that this would be another solution and would greatly increase the angle I could run)

As always, your thoughts/suggestions are greatly appreciated.

Lastly, I mounted a GoPro on my front sway bar to get a look under the vehicle, this will give you an idea of what I am hearing during deceleration primarily. Listen for the dramatic grrrrrr when I let off the gas...the rest is pretty much tire noise.

 

[bryson]

The joint angles need to be equal/parallel for the stock-style rear DS to run smoothly - i.e. the rear pinion and the rear t-case output need to be parallel so the DS joint vibes cancel each other out. If they aren't parallel, you'll wear out u-joints and pinion/t-case bearings prematurely, so I wouldn't run it like that too long.

If you run a DC rear shaft, you would have to modify the control arms so the rear pinion points at the t-case output - i.e. the DS and the pinion must be in line.

It sounds like either option will require adjustable control arms to dial it in 100%.

 

[MrMoose]

I installed adjusted lower control arms on mine when I went with a 4" heavy load lift. I don't have any vibrations, and still have a bit of stinkbug look with the heavier springs in the rear. The adjustable LCA's will help bring the pinion angle to where it needs to be.

 

[baldilocks]

Is the front pinion angle zero as it needs to be wth the DC? Are you sure all vibes are from the rear? Sounds like you need a DC shaft in the rear with zero angle at the pinion which dictates rear adjustable upper and lower control arms. My 80 is not that tall but I bought the metaltech rear adjustables to push the axle back where it's supposed to be not to mention my stock arms were bowed from dragging them over rocks. The MT's are made of .250 thick DOM and really not a bad price compared to what it would cost you to source the same parts and spend the time to build your own. My 2 cents.

 

[Hunyuk]

First, I am not 100% sure that the vibration is coming from the rear. I originally thought it was the front, but was convinced otherwise. Unfortunately I am not equipped with CDL (yet) so I can't pull the front drive shaft to verify. My front pinion angle is damn near zero, but not zero. I am going to install the sliders and transfer case belly plate this week, see if it makes any difference. Also going to load the rear end with 250-300 pounds and see what difference that makes.

 

[bmac1996acc]

I flipped my rear driveshaft (connect pinion end to transfer case) after talking to Brian at ACC. The grrrr went away without correcting pinion angle (which I did later).

 

[bryson]

If your front angle is 0* with a DC shaft that could be your issue... The front pinion and DS need to be in line for a DC to run smoothly. My front DS makes a noise that is similar to what you're experiencing, resonates through the chassis, and could be easily mistaken for something else.

 

[Hunyuk]

If your front angle is 0* with a DC shaft that could be your issue... The front pinion and DS need to be in line for a DC to run smoothly. My front DS makes a noise that is similar to what you're experiencing, resonates through the chassis, and could be easily mistaken for something else.

Yes, if I had to describe it, it's a vibration resonating directly under my feet when I take my foot off the gas (or re-apply), coupled with the "grrr" sound.

 

[Hunyuk]

I flipped my rear driveshaft (connect pinion end to transfer case) after talking to Brian at ACC. The grrrr went away without correcting pinion angle (which I did later).

No kidding? So you have your slip yoke at the pinion in the rear?

 

[MrMoose]

In you've done the pin 7 mod, you could just pull each shaft separately and find the source. Better than just throwin money at it.

I'd check the rear first since you haven't made any adjustments to the pinion angle.

 

[bryson]

Since you don't have a CDL switch yet, put the t-case in low range while the vehicle is running to engage the CDL, shut off the vehicle then pull the diff fuse. This will allow you to put the t-case back into high range but keep the CDL locked. Pull the front shaft and drive around. If the noise is gone, the front shaft/angle is your issue. Or plug your hazard switch into the CDL harness for a temporary CDL switch.

 

[Hunyuk]

Since you don't have a CDL switch yet, put the t-case in low range while the vehicle is running to engage the CDL, shut off the vehicle then pull the diff fuse. This will allow you to put the t-case back into high range but keep the CDL locked. Pull the front shaft and drive around. If the noise is gone, the front shaft/angle is your issue. Or plug your hazard switch into the CDL harness for a temporary CDL switch.

Wow, now that's thinking! I'll give this a try when I have some time later this week.

 

[BVCOTaco]

I like the hazard switch idea too!

 

[landtank]

go to harbor freight and get a digital angle finder and check the angles of the u-joints. I have a thread on here on how to determine the operating angle of the front u-joint of the front shaft for a DC installation. The rear is as simple as having the flanges equal to each other.

It won't rule out a drive shaft and you still should pull them to make sure you have the right end of the drive train.

 

[ALX4X4]

Could I ask who did the front DC shaft for you ? I need one in Australia, have e-maiiled Tatton but no answer. My stock shaft complains when the front axle is on full droop with power applied. New uni's helped, but it's still not happy so I'm going to have to try a DC. TIA.

 

[bajaphile]

It has been suggested to put some weight (sand bags, or similar) in the back and to shorten (although I think I actually need to lengthen) the rear upper control arms to temporarily reduce the angle. I'm posting here looking for suggestions, and have a few questions too.

For the uppers you need to shorten them to push the pinion angle down back towards the ground. Metal tech and Slee both sell these. Or there are some good ideas here on making your own.

 

[Hunyuk]

Could I ask who did the front DC shaft for you ? I need one in Australia, have e-maiiled Tatton but no answer. My stock shaft complains when the front axle is on full droop with power applied. New uni's helped, but it's still not happy so I'm going to have to try a DC. TIA.

I got my 6" lift from Slee Offroad which included a new front DC DS.

 

[baldilocks]

Could I ask who did the front DC shaft for you ? I need one in Australia, have e-maiiled Tatton but no answer. My stock shaft complains when the front axle is on full droop with power applied. New uni's helped, but it's still not happy so I'm going to have to try a DC. TIA.

I had mine built at a shop here in Sacramento. A Spicer 1310 CV/DC joint has a bolt pattern that fits perfectly over the studs of the HF2AV t-case. They did have to machine the CV flange to remove a slight amount of thickness so a couple threads of the studs would protrude through the nuts when the DS was installed. No issues yet.

 

[lazy]

I have a 4" lift w/ heavies. I had the same noise and replaced the front with a Tatton DC DS (Slee won't sell them outside of their lift kits). I still had a bit of noise and purchased the Slee adjustable UCA's. After installing the UCA's and making them a bit longer, the pinion lines up with the rear DS and no more noise! Did you not get the adjustable UCA's with your Slee kit?

Note, I was going to purchase the DIY weld on sleeves, but Slee was out of stock and had no idea when they would get a new batch (they threw out months). But, they did just lower the price on their bolt on adjustable UCA's to $375....Tatton will make you a rear DC DS for $325, but you still have the pinion/DS angle to address....

@ALX4X4 - have you tried ordering from Tatton via ebay?

 

[ALX4X4]

Once I order from Tatton on e-bay I'm locked in. I messaged then through e-bay via the 'ask seller a question' and no reply, 2 months later. Hardly confidence inspiring to then order and ask questions if they only pay attention once they've got your money 10,000 miles away :-(
Bit disappointing as I'd read good stuff about their shafts on mud. I'm getting new Superior 4" lift radius arms this week to correct my castor, so at least I'll have accurate flange measurements once the axle is pushed forward and cc'd. Sorry for hijack, but just not sure on laying money down with Tatton and then maybe not getting the answers I was seeking. Have to 'buy it now' before I get a reply I reckon. And AUD offering 0.70-ish means it's way over $500 by the time it gets here.