Bad vibration in 4x4 under acceleration

[Karo]

Additional information: I have the 2" BDS suspension kit with bilsteins and the 88 springs in front, no additional spacer on top of the strut.

[Trail X]

Now that we know that it is the cv's what do we do about it I got Mark's 3'' lift it did not seem to do it with his 2.5'' lift when i had it in but that has been some time ago that i had it so now what

Not sure we can without a doubt jump to the conclusion that it's the CVs, but it does tell us that it's not a rotational vibration of the transfer case, drive shaft, or diff.

The vibration is most likely a result of torque being transferred through a joint. The torque is somehow exacerbating a surface imperfection on a sliding or rolling surface (or there's not enough rolling surface), or it's binding up a joint in a way that the joint no longer creates a linear relationship between the two sides of the joint.

At least - that's what it tells me.

Opeth, since your CVs are out, I'd tear them down completely, and inspect your rollers, balls, and all rolling surfaces for imperfections or wear.

[Opeth]

The vibration is most likely a result of torque being transferred through a joint. The torque is somehow exacerbating a surface imperfection on a sliding or rolling surface (or there's not enough rolling surface), or it's binding up a joint in a way that the joint no longer creates a linear relationship between the two sides of the joint.

Exactly, or it might also be the roller bearing surface coming out of its race surface. If we had an option between a tripod style joint or another style like a ball and race ( Porsche 930 joint) the extra surface area might cure our issue along with a longer overall length..

I've done some more digging and found that the left inner output cv flange from a astro, safari, blazer 96 and older 4x4 has a 26 spline 6 bolt flange which would mate to a Porsche 930 joint, but requires a machine shop to match our bearing surface size. See post below for work required.

http://forums.txzr2.com/viewtopic.php?f=23&t=2130

I'm still trying to find out if we would have enough clearance with that big flange next to the disconnect actuator motor, I can't find any overall length dimensions on that flange and I think it would be luck of the draw trying to even find that part. I've looked on a couple gm part sites and they list the part, no part number. You'd have to find them in the junk yard me thinks. I'm trying to find us the cheapest route without having to pay big bucks for custom made shafts.

I think I might start a whole new thread on this topic and findings as I go. Thoughts?

[v7guy]

Opeth, since your CVs are out, I'd... inspect your ... balls, and all rolling surfaces for imperfections or wear.

I really couldn't help myself, it was a long night at work.


I don't think a thread documenting the exploration of a more suitable CV would be a bad thing. I've got some info I've pieced together over the last year, but I've been keeping it to myself since nothing has really panned out and there doesn't seem to be a tremendous amount of interest in exploring the IFS beyond our current accepted limits.

I think the mention of the bearing coming out of the race is unfounded. When I rebuilt the CVs I posted a pic of the tripot at a crazy angle and it was commented that it was too bad they wouldn't function like that. But even at that angle even the top bearing was still at least half way in the tripot. I would easily buy that the additional angle has created more slop in the tripot, or if the axle had banged on the tripot housing (due to lesser clearance of the aftermarket unit) it could have even tweaked the tripot causing the slop and then the vibration.

I still keep coming back to it's strange that I don't personally feel it.

[prepper1212]

i know this thread is over a year old. i am just wondering if there has been any more info on this problem. the day i put marks 2.5 lift on mine started the vibration. i have noticed that some times it is there in 2wd .a4wd. and 4hi. also i have done a alignment but i did not flip the uca . i believe the drivers side seems worse on my tb i am returning to the shop to get the alignment redone as after 200 mi my tires are starting to cup on the out side. i will keep everyone informed as i head forward with this problem

[Opeth]

Its the CV shaft angles, I drove around with both sides out and issue was no longer there. Replaced with aftermarket cv's and shakes were a little less noticeable... off pavement I can't notice it, pavement with snow I can slightly feel it.

[Trail X]

Is the inner tripod joint allowing the shaf to hit the housing?

[prepper1212]

thanks i have a appointment on sat to have the alignment redone . i will just take the vibration as normal after the lift. if i had the funds i would like to redesign the oil pan and the center shaft set up to allow for a better angle.

[Opeth]

Is the inner tripod joint allowing the shaf to hit the housing?

Nope.

[Bacnbit]

I am amazed so many suggest alignment. Rediculous... Alignments dont cause vibrations on excell it would have to be violently out and you could see it by eye.
Pull the prop shaft and redrive if vibration is gone. Prop shaft needs rebuild or Tcase has an issue. More than likely propshaft. Even if you regreased it could be worn enough. If its CV type its problably toast. If this is truely a 4wd engaged vibration only.

[HARDTRAILZ]

I am amazed so many suggest alignment. Rediculous... Alignments dont cause vibrations on excell it would have to be violently out and you could see it by eye.

Bullshit. I had it happen.

I had same vibrations on acceleration, got the alignment done and the vibration never appeared again. It may have appeared a bit out of alignment, but not violently and not enough most would have noticed it by sight.

[Bacnbit]

I am amazed so many suggest alignment. Rediculous... Alignments dont cause vibrations on excell it would have to be violently out and you could see it by eye.

Bullshit. I had it happen.

I had same vibrations on acceleration, got the alignment done and the vibration never appeared again. It may have appeared a bit out of alignment, but not violently and not enough most would have noticed it by sight.

Well then I stand corrected.
For the small % of people that alignment repaired. I would have loved to see the before specs. Just watched a lot of people align vehicles for vibrations and not have there problem fixed or wont take the advise of the technician.
There are so many variables when dealing with altered vehicles.
The rotational mass of so many parts that need the correct Geometry to function correctly is crazy with modifications.
I will be the first to claim I dont now Sh!@. But give me a day or 2 with it and my boys and I could figure it out.

[HARDTRAILZ]

Mine are posted on this forum if you want to see the before and after specs.

[Bacnbit]

Mine are posted on this forum if you want to see the before and after specs.

Sweet. Now tell the dumb guy how to find it. LOL
BTW enjoyed your build Nice TB. Hope mine ends up half as nice as some of the beauty's on here someday.

[HARDTRAILZ]

Search button at top of page. That's what I would do. Been years so not sure what thread its in.

Alignment before after be good terms to start with.

[Bacnbit]

WOW
I can see vibrations here. This is not yours. But the couple I did find look very simuliar.
Camber and Toe this far out yes vibration on excell when the tires camber off slightly.
Does anyone ever take the time to modify to correct caster or do they just live with someone telling them caster doesnt affect tire wear BS? And an alignment tech that was taught The "green and go method".
I would hope everyone is having their alignments done or checked a couple times a year with the modifications and more so for the guys wheeling. To protect their Tire investments.
And no I don't work at a tire store. LOL

[Trail X]

Caster is adjustable by the lower control arm mount plate. For some reason many techs don't seem to understand that though and seem to skip it.

I really need a new alignment, but I'm going to wait until I get a new set of tires. I did an eyeball alignment and its good enough for now.

[HARDTRAILZ]

WOW
I can see vibrations here. This is not yours. But the couple I did find look very simuliar.
Camber and Toe this far out yes vibration on excell when the tires camber off slightly.
Does anyone ever take the time to slot the upper strut mount to correct caster or do they just live with someone telling them caster doesnt affect tire wear BS? And an alignment tech that was taught The "green and go method".
I would hope everyone is having their alignments done or checked a couple times a year with the modifications and more so for the guys wheeling. To protect their Tire investments.
And no I don't work at a tire store. LOL

I will be the first to claim I dont now Sh!@.

You summed it up well. I would not ever advise slotting the upper mount. Caster does not affect it in as minimal as we end up with. Been proven out for years. Its able to be within a tenth of a degree or so; possibly even in spec with a decent alignment tech. Most do not know it has some adjustment available.


I have not had an alignment in a couple years...other myself doing it in the driveway. I do have a lifetime alignment at firestone, but its 40+ miles to one now and my tires are wearing great. Will eventually make an appointment, but with the multitude of mods and fairly decent wheeling I do...I am just fine with how it is handled.

[Bacnbit]

WOW
I can see vibrations here. This is not yours. But the couple I did find look very simuliar.
Camber and Toe this far out yes vibration on excell when the tires camber off slightly.
Does anyone ever take the time to slot the upper strut mount to correct caster or do they just live with someone telling them caster doesnt affect tire wear BS? And an alignment tech that was taught The "green and go method".
I would hope everyone is having their alignments done or checked a couple times a year with the modifications and more so for the guys wheeling. To protect their Tire investments.
And no I don't work at a tire store. LOL

I will be the first to claim I dont now Sh!@.

You summed it up well. I would not ever advise slotting the upper mount. Caster does not affect it in as minimal as we end up with. Been proven out for years. Its able to be within a tenth of a degree or so; possibly even in spec with a decent alignment tech. Most do not know it has some adjustment available.


I have not had an alignment in a couple years...other myself doing it in the driveway. I do have a lifetime alignment at firestone, but its 40+ miles to one now and my tires are wearing great. Will eventually make an appointment, but with the multitude of mods and fairly decent wheeling I do...I am just fine with how it is handled.

Yeah I took the slotting out of the post after looking at how it all goes together a minute sorry for that and thank you James for pointing that out.

[Opeth]

Live with the caster or go through upper ball joints with their extreme angle. My tires are wearing just fine and that spec sheet is mine.