FJ62 Vibrations on Acceleration

[franklin40]

yep i’m thinking that too. they are running at a steeper angle now and out of where they had worn them selves. a little binding will cause a noticeable vibration. if the suspension kit was designed well (sounds like it was) then the shackles would have kept the flanges parallel despite the lift. they’re darn close anyway. i’d change out u joints next to see if that takes care of it

 

[atlshaun]

I took some measurements using a digital angle gauge and found that they were only 0.8 degrees out of parallel from each other. I used the ground as reference. Is this enough difference that would cause an issue?


1. They are the OEM wheels and they do have weights on them from the PO. I do see that the interior of the wheels are painted. Could this be an issue?

2. When I changed the oil seal, I did torque the nut to spec, but I only staked it at the location it was staked at previously. I did not want to tighten any further as I read that this could affect the preload. Could this affect the how the pinion operates? Prior to the vibrations, there was a slight hum coming from the rear diff that wasn't an issue, but nowI am not sure if it all could be related. I did also make sure to mark the shaft and companion flange to make sure it was all properly aligned. I did the same as I removed the driveshaft completely to make sure they can be aligned again


Hi Franklin, I measured the angles at the output flange and pinion flange and found that there is only a difference of 0.8 degrees. I used a digital angle finder and used the floor as reference. Would this cause the vibration issues? Should I still be looking at shims?


Oh man, did this also happen right after installing a lift?


I am unsure as well. I am wondering if the issue is with the pinion angle as you mentioned or the pinion itself. If it is the angle, would you suggest using shims as others have suggested? Could it be possible that there is an issue with the pinion itself?

Technically, yes

But I basically put the new lift on as soon as I got mine so I am not too familiar with what it did pre-lift

I will say having those u-joints replaced and the driveshaft balanced did more for my trucks drive ability than anything I have done

ymmv

 

[pborrica]

It could well be coming from an part worn universal joint.
The uj wears in the angle range it is predominantly working in, now it is out of it's "comfort zone" and has to accept a tiny bit more angulation.
Once you apply a load the little needles (inside the four uj bearing pots) are trying to move back into their worn in places - resulting in a stiffening of the uj and consequently creating vibrations.
I had exact that scenario before and new uj's fixed the problem

yep i’m thinking that too. they are running at a steeper angle now and out of where they had worn them selves. a little binding will cause a noticeable vibration. if the suspension kit was designed well (sounds like it was) then the shackles would have kept the flanges parallel despite the lift. they’re darn close anyway. i’d change out u joints next to see if that takes care of it

Technically, yes

But I basically put the new lift on as soon as I got mine so I am not too familiar with what it did pre-lift

I will say having those u-joints replaced and the driveshaft balanced did more for my trucks drive ability than anything I have done

ymmv

Hey everyone, just wanted express again how much I greatly appreciate everyone's help on this! To give an update, I was finally able to replace the u joints in the rear driveshaft this past weekend. U joints were purchased from Cruiserteq. Unfortunately, the issue still persists. However, the vibrations do feel less aggressive this time around. We're definitely going in the right direction. Any advice on the next steps? Should I possibly be looking into shimming?

 

[Old Nick]

Hey everyone, just wanted express again how much I greatly appreciate everyone's help on this! To give an update, I was finally able to replace the u joints in the rear driveshaft this past weekend. U joints were purchased from Cruiserteq. Unfortunately, the issue still persists. However, the vibrations do feel less aggressive this time around. We're definitely going in the right direction. Any advice on the next steps? Should I possibly be looking into shimming?

Yes, look at shimming.

Also, I can't recall if anyone mentioned this above (but I bet they did), have you considered have your drive-shaft balanced?

 

[relaxedcruiser]

I don't know if that was discussed before here - are you free wheel hubs unlocked ? Otherwise the vibration could also come from the front shaft.
If you didn't experienced any vibrations before you fitted the lift - then there should be no need to get it balanced after the lift ...
Is the phasing of your yokes in line ?
Sorry - If that was mentioned above...I rust read that you still have issues, hope you get a smooth ride soon.

 

[bcolvin]

I don't know if that was discussed before here - are you free wheel hubs unlocked ? Otherwise the vibration could also come from the front shaft.
If you didn't experienced any vibrations before you fitted the lift - then there should be no need to get it balanced after the lift ...
Is the phasing of your yokes in line ?
Sorry - If that was mentioned above...I rust read that you still have issues, hope you get a smooth ride soon.

I had been chasing down the same issue for awhile. I did the same steps. My issue resolved with shims in the rear. I tried shimming the rear diff down which was the common thought. This did not work. I flipped the shims the other way around and totally fixed my issue. This had everything to do with drive line angles. Since I could not angle the t case down bringing up the diff solved the vibrations. I ordered my shims from valley hybrids.

First make sure it is your rear shaft. Pull the rear shaft and Drive in 4wheel. If it is smooth. Order the shims, slap them in, see if it makes it better or worse. If worse flip them. If that does not keep digging

 

[pborrica]

Yes, look at shimming.

Also, I can't recall if anyone mentioned this above (but I bet they did), have you considered have your drive-shaft balanced?

Others have mentioned it previously, so I think that will be where I'll start looking into next. Thanks! Hoping either of those two can solve our issues.

I don't know if that was discussed before here - are you free wheel hubs unlocked ? Otherwise the vibration could also come from the front shaft.
If you didn't experienced any vibrations before you fitted the lift - then there should be no need to get it balanced after the lift ...
Is the phasing of your yokes in line ?
Sorry - If that was mentioned above...I rust read that you still have issues, hope you get a smooth ride soon.

Not a problem happy to accept any help! I can confirm that the hubs are unlocked. I did lock them when I was trying to pinpoint the issue originally. However, they have since been unlocked after reinstalling the rear driveshaft with the new u joints. I was thinking the same since I wasn't experiencing any vibrations before the lift, but others have mentioned that it may be worth looking into. The yokes phasing should be in line, but I'll take a closer look and get back to you

I had been chasing down the same issue for awhile. I did the same steps. My issue resolved with shims in the rear. I tried shimming the rear diff down which was the common thought. This did not work. I flipped the shims the other way around and totally fixed my issue. This had everything to do with drive line angles. Since I could not angle the t case down bringing up the diff solved the vibrations. I ordered my shims from valley hybrids.

First make sure it is your rear shaft. Pull the rear shaft and Drive in 4wheel. If it is smooth. Order the shims, slap them in, see if it makes it better or worse. If worse flip them. If that does not keep digging

Thanks for the advice! I'm glad you were able to get your issues resolved. It sounds very much like what I'm going through right now. I'll definitely look at getting some shims. Do you know the specific shims you purchased or the specs on them? I don't have too much experience with them, but I imagine there are different various ones with different angles and lengths?

I was able to pinpoint that the issues was somewhere in the rear through the 4wheel/front wheel method. I removed the rear drive shaft, drove it in 4wheel/front wheel, and the vibrations when away. I'll definitely take a look at shimming and hope for the best! Thanks!

 

[GRpufnstuf]

but why would it start vibrating immediately after the lift. that doesn’t sound like a u joint/ drive shaft balance problem. maybe it accentuated a bad u joint but it’s not going to make a u joint go bad or drive shaft go out of balance but putting a lift on. it’s a change in pinion angle causing angular rotation differences

if the T-case output flange and the pinion flange aren't parallel to each other there will be vibration. U-joints act very oddly when the rotate. There is a part of the turn that is "faster" and part that's slower. If the front and rear joints aren't sync'd up they will vibrate. They maybe aren't broken yet but they soon will be.
Best to get and angle gauge on the drive flanges and then get the axle shimmed. Also replacing u-joints and pinion seal while in there.

 

[franklin40]

yep that’s what i was getting at. if the two u joints don’t turn at exactly the same angle then they don’t have the same acceleration/deceleration to balance eachother and they’ll vibrate. the flanges need to be parallel and some lifts don’t account for this change so need either a different length shackle or a shim to line the pinion flange up with the out put flange.

all that being said i could see how after a ujount has run in and now is being run at a higher angle after the lift it could possibly become a factor but in my experience my vibrations have always been fixed with proper shims.

 

[bcolvin]

The shims I went with were 4 degrees from cruiserbros/valley hybrids. I first shimmed up my t case which made the issue significantly worse. Then I removed that shim and put the rear diff shims in reverse of everything I’ve read. This made significant improvements with 2 degree but there was still some vibrations. I then ordered the 4 and everything has been good since.

That was really the end of that saga… I replaced everything that I could think of thinking I would eventually find the root. Not until getting a bit creative did I get traction on the issue. Also I measured so many times drive line angles but must not have ever really got it right. Good luck and report how it goes!

 

[franklin40]

if you can get steel shims do it. i did aluminum once and it’s amazing how fast they can cause corrosion agains the steel (especially if you have any salt on your roads). the steel on steel won’t cause the same issue even though they will rust they won’t continue to erode at the same pace.

 

[BurntToast]

if you can get steel shims do it. i did aluminum once and it’s amazing how fast they can cause corrosion agains the steel (especially if you have any salt on your roads). the steel on steel won’t cause the same issue even though they will rust they won’t continue to erode at the same pace.

Galvanic corrosion is a hell of a thing

 

[pborrica]

Hey everyone, sorry for being MIA. Just wanted to provide an update. I got to a point where I couldn't solve the issue on my own, so I finally took the cruiser to a local auto shop nearby. They had done all they could (driveshaft balance, torqued motor mounts, torqued all bolts, etc), but they couldn't figure it out. At this point I decided to install some steel shims that many some folks recommended here. Now I can report that the violent vibrations are virtually gone! Thank you for everyone's help! You guys are awesome! Hopefully this thread can also help others running into similar issues

 

[toy_tek]

Good to hear. I’ve got 2.5* shims waiting for some time to install, in order to solve this same issue that popped up after installing my lift.

This link was posted on another thread and the videos pretty clearly explain what’s going on and why the flanges need to be parallel to each other. Right now my flanges measure about 2.2* difference from one another.

Driveline Geometry 101

Driveshaft Angle Explained This video will demonstrate the proper angles for a drive shaft in a stock Jeep or Truck and how the rules change when you add a suspension lift. The video below demonstrates what is happening to the shaft at different angles, how improper angles can cause speed...

4xshaft.com

 

[stevebotag]

Hey everyone, sorry for being MIA. Just wanted to provide an update. I got to a point where I couldn't solve the issue on my own, so I finally took the cruiser to a local auto shop nearby. They had done all they could (driveshaft balance, torqued motor mounts, torqued all bolts, etc), but they couldn't figure it out. At this point I decided to install some steel shims that many some folks recommended here. Now I can report that the violent vibrations are virtually gone! Thank you for everyone's help! You guys are awesome! Hopefully this thread can also help others running into similar issues

Apologies for the newbie question but where do the shims get installed?? Does anyone have a link to an installation video? I’m quite competent mechanically so I’ll check the difference in the two flanges when I pull the DS for U Joint replacement… appreciate it

 

[dbleon]

They go between the leaf pack and the axle perch. You’ll likely need longer center bolts… you want to bolt the shim onto the leaf pack. Fat end of the shim facing forward will raise the pinion up.. fat end to the rear will lower the pinion angle