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Discussion Starter #1
Whats up fellas. First off, I used the search function lol and found a lot of people that had the same issue such as this thread here but most never posted a solution or lived with it:

http://www.clubfrontier.org/forums/f26/2010-pro4x-lift-changed-drive-shaft-line-angles-help-61623/

Basically I am having the same issue as the poster in the above mentioned thread on my 2014 Pro4x. I only have a slight vibration at take off but if I take off slowly it's not there. I am very picky with my truck and because its new and my only vehicle (other than the wife's camry) I can't afford any breakage later on.

I recently installed the rough country 2.5" front spacers and PRG adjustable shackles (highest setting 2"). Truck sits fenders to floor at 36.5F/37R and before at 34F/35R. Afterwards I started to have the vibration issue. After reading many threads of other having the similar issue, I have concluded that I will need either:

1. 2" tapered blocks (which I don't want to since I like the shackles) or,
2. Rear axle degree shims.

My question is the degree angle. I have seen 2, 2.5, 3, 3.5, 4 degrees. For a mild lift like mine, which angle do I need to stop the vibration. I saw a thread that mentioned 1.5" rear lift needed 2 degrees but just wanted more opinions before purchasing 2 degree shims at pepboys. Anything more I need to go with Nisstech shims. There's about a 1/4" of thread left on the U-bolts to maybe squeeze these in. If not where can I get slightly longer than stock.

Last question. Anyone know where I can purchase a stock lower strut bolt/nut other than my local dealer. I have a gut feeling my drivers side is stripped cause the it went on very slow and the passenger side was a breeze.

Much help is appreciated. I will post a pic of my truck with the stance later.
 

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Not a 4x4 expert but am pretty good with cars all around. pinion angle would be the FIRST place I'd check lifting with longer shackles. Not only are you lifting, you're re-angling the axle by only lifting one end of the leaf.



What do you mean the bolt "went on slow"? were you using power tools to install it?! (Sorry, pet peeve from having to fix it when other people do that and jack up fasteners. over and over) Find the thread pitch and length and go get the highest rated bolt that matches from the hardware store. Also get a thread repair kit for the hole it goes in if it isn't replaceable (IE: a nut)
 

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Discussion Starter #3 (Edited)
Thanks Russell. I just went to Pepboys and pick-up some 2 degree shims however I have to return them cause they don't have the hole cut out for the leaf bolt. However, advanced auto parts has the shims with a cut out. I will try these out today and if it reduces or eliminates the vibration I will let you all know. If its reduced then I will have to advance to 2.5-3 degree shims.

Yea the bolt went in ok at first then it slowed down... I hand turn it first then hit with the impact gun. The other side went on perfectly fine. Anyways, I will just replace that bolt since it lingers in the back of my mind.
 

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Discussion Starter #4
Well I installed the new 2 degree shims from Pepboys (they did have the cut out after all). The vibration reduced somewhat. Only $10 btw...

I have a theory. Because I added such a long shackle, the vibration I'm getting is more of a rear wobbly feeling. I'm thinking that the torque of the drive axle on a good take off is making the truck wobble in the rear. Only happens up to 20mph then smooths out. I might experiment with 2" tapered blocks now. However the angle of the pinion is much better now.
 

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Discussion Starter #5 (Edited)
Little update. Mr. Nomad 13 has informed me that I installed my shims backwards (thick part in rear) when it should be thick part in front to drop the nose of the pinion back down. I will redo this as soon as I get out of work.

I thought the pinion was to be a straight line with the axle. I was wrong... If this doesn't work, I am switching to Deaver AAL's and selling the shackles. Lets see.

-UPDATE-

I flipped the 2 degree shims (thick part towards the front), as Nomad 13 had suggested I'd do in a pm, and I have no more vibrations in the rear axle/pinion. I bought these from pepboys for $10 and install was very easy and quick. I only used a jack, jack stand, 18/22mm socket and my ryobi Impact driver (saves so much time). The oem U-bolts are long enough to fit the shims into place you will need to adjust the 4 18mm bolts and be sure they are equally tightened and have the same spacing on the U-bolts.

So my understanding is adding 2" shackles as I did dropped the rear pinion gear down changing the drive angle. To correct the angle add a shim with the thick part towards the front to drop the front of the pinion and correct the angle.

Glad this was able to turn out the way it did cause the truck coast smoothly now, before you can feel it slow down due to the change in drivetrain. Next summer I'm upgrading to coil overs and leaf packs. For now, I'm happy with the stance.
 

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You want the pinion to driveshaft angle to be the same as the transmission to driveshaft angle. If not, the angular acceleration imparted on the driveshaft isn't canceled out. Having equal angles on both ends of the driveshaft, only the driveshaft varies in speed. Wrong angle on the U-joints (or not aligned in a multi-piece DS) will pass that speed variation to the axle and drive wheels which you feel as a vibration.

EDIT: removed silly notions from not paying attention.
 

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Curious. When I installed my lift blocked, which are wedged, I was told by everyone to have the thick side face toward the rear of the truck. Is this different with blocks vs. shackles? Or did everyone tell me to install them wrong?
 

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Discussion Starter #8
Curious. When I installed my lift blocked, which are wedged, I was told by everyone to have the thick side face toward the rear of the truck. Is this different with blocks vs. shackles? Or did everyone tell me to install them wrong?
Man this has been a huge puzzle that was finally solved for me. I searched google pictures and forum pictures and saw shims installed with the thick part towards the rear.

After talking to Nomad it made sense that I had them wrong. I never installed blocks before but with the shackles, the rear of the pinion dropped so now I had to drop the front to correct the change so as soon as I changed the shims around, smoothness. The truck actually coast down the street quiet smoothly too.
 

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Curious. When I installed my lift blocked, which are wedged, I was told by everyone to have the thick side face toward the rear of the truck. Is this different with blocks vs. shackles? Or did everyone tell me to install them wrong?
Just saw your PM but I'll answer here so it's public.
The reason most kits make larger blocks in a wedge shape is to cut down on drive shaft angle, NOT necessarily u-joint angles. When you drop the rear axle more than a couple inches people are concerned that the drive shaft will be at too much of an angle. Not sure why as this is less of a problem than having one u-joint angle being different than the other as was stated above until you get close to 4* angles and beyond. At that point you're better off going to CV/cardon joints as u-joints don't last long in those extreme angles. Ideally you want the trans/DS angle to cancel out the DS/pinion angle (one angles down 3* and the other angles back up 3*).
Some larger kits (like DB kits) also do it for clearance issues so keep that in mind.
So yes, the block will be installed with the thicker part to the rear while a pinion shim will be installed with the thicker part towards the front in most cases.
If it's just a 2-2.5" block there is no reason why you can't install a flat one as apposed to a wedge shaped one. Any more than that and you'll need the little bit of angle to keep your DS clear of the cross member and keep from having to add length to your DS.
My current set up uses 7" of rear lift and I get no vibrations whatsoever. My PRG shackles are set in the middle (1") setting so the pinion is angled up just slightly but not enough to cause any vibrations. I did have to have the DS made 1/2" longer to compensate for the extra drop between the output shaft and the pinion.
Just FYI, we fronty owners do have an issue with limited clearance between the drive shaft and the DS hoop/cross member right behind the trans/t-case especially on 4x4s so if you lift the rear too far you have to go to a smaller diameter DS like I did.

I have no vibration or noise from the u-joints, so I guess on blocks it's different than if you did shackles.
Yes, the difference is that blocks don't change the pinion angle until they are big enough to need to be wedge shaped. As long as the axle moves straight down from the center line (as in the case of blocks) you don't need to adjust for pinion angle change.
In the case of shackles you are only lengthening one attachment point for the leafs which drastically changes the pinion angle and thus the rear u-joint angle. This causes vibrations. Adding the shim to bring the front of the pinion back down gets the angle back to where they cancel each other out again.
 

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I would have thought that lowering the rear of the leaf would be canceled out by raising the rear of the axle (how you had the shims initially) but as I said, no 4x modding experience.
This is exactly what putting that shim in thick side forward does. Remember, our axles are mounted spring over axle. For a spring under set up the thick part would go towards the rear.
Since you can't raise the rear of the axle housing back up without shortening the shackle the only option is the drop the front in order to rotate the axle housing forward. Thus the angled shims go in with the thick side in front ; )
 

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This is exactly what putting that shim in thick side forward does. Remember, our axles are mounted spring over axle. For a spring under set up the thick part would go towards the rear.
Since you can't raise the rear of the axle housing back up without shortening the shackle the only option is the drop the front in order to rotate the axle housing forward. Thus the angled shims go in with the thick side in front ; )
D'OH.

last 3 trucks were axle-over-leaf. Silly me. ::wink:: Better to be inattentive than going crazy, right?
 

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I just installed 2" non- tapered blocks in rear of my truck along with 2.5" spacers up front. I might have a very, very slight vibration while coasting as my speed comes down at 35mph - 30mph. So slight I'm not even sure its there. The transfer case yoke has come out about 3/4" - 1" after lift. Is this anything to worry about?
2017 SV CC auto. 4x4. Thanks in advance for any advice.
 

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I’m so psyched that I found this thread. Thank you, @JLP0128 @Nomad 13
I’ve been searching for hours trying to figure out some logic to all this. And, this thread is so helpful. I have a 1.5” lift shakle and definitely felt a slight vibe at lower speeds after installing. Never minded it because it was so slight. Then, added an AAL by ReadyLift which states 1.5-2” of lift, which I personally feel got me somewhere around 2.5-3”. Making it between 4-4.5 of lift at the rear.
I mentioned in a post I’d made earlier that I didn’t think to measure fender height because I wasn’t installing the leaf for lift, I was doing it to support the weight of my RTT, modular bedrack, trail jack, and box of camping gear and fluids.
As soon as everything settled after installing the leaf, I could tell there was a pitch change at the rear diff. I’ve been eyeing it everyday since. It’s been really windy this whole week and that’s when I really began to feel them and I could feel them vibes through and through.
Even at the height the rear is now the vibes aren’t all too bad, but I could feel how much harder the driveline is working and I feel them every time I accelerate. They do go away when I let off the accelerator.
After reading all this I now will be looking into what shim I will need to correct the pinion angle for my set up. As well as installing bend-over spring clamps from under the AAL to the main leaf pack to keep those aligned and using the bolt on spring clamps about 2.5-3” from the front and rear of the axle to tie the rebound leaf into the entire pack because I feel this AAL is another factor in the rear vibes. But, my guess is the pinion angle will cancel out most of them, if not all.
 
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