thezentree

I lifted my 4Runner a few weeks ago (3" Toytec Eibach w/ diff drop) adn put 285 KO2s on OEM 5 stars. Since then I've had a bad vibration at highway speeds. I've had the wheels and tires road force balanced twice and different shops and replaced the driveshaft with a Tom Woods double cardan shaft, with no improvement.

I checked the pinion angle yesterday and found that the pinion and driveshaft have about a 5° difference in angle - is this enough angle to cause that vibration?

If so, is this common and people are just living with it? I've gone through a bunch of build threads and not seen hardly anyone talk about this.

Acorn22

I'm at about 4.5" lifted in the rear and don't have a vibration even going 70+ on the highway. I would say check the u-joints, but you have a new driveshaft so that doesn't make any sense... Did you do a panhard bar drop? That is the only other thing I can think of that could maybe throw off alignment slightly.

thezentree

No drop bracket but I've got an adjustable panhard bar on it, and it's within 1/16" measured from the edge of the tread to the fender. I loaded it down with about 500lbs of sand bags yesterday and got the pinion angle to within 3degrees and the vibration didn't change, so I've pretty much ruled out the rear driveshaft as the culprit. Also replaced both CV axles this weekend, again no change.

I dropped it off at the tire shop last night and asked them to check runout on the tires.

I don't really know what else to check at this point.

Acorn22

When you installed the driveshaft, did you (or a shop) ever take the slip yoke out to grease it? If so, maybe it wasn't put back correctly aligned and the driveshaft is out of balance.

I'm really thinking it has gotta do with the wheels though, I bought a set of BFG AT2's like 6 months ago that I could not balance to save my life and I talked to 4wheelparts about it, which is where I got them, and they said BFG has an incorrect molding for the tires and MANY people have been taking them back because they can't be balanced. Now I don't know if this is just with the AT2 and has nothing to do with your KO2, but just thought I would share that with you that BFG is passing off messed up molds to be sold and that this was my experience with them

thezentree

I think you're right. I picked it up from the tire shop this afternoon after they rotated, road force balanced, and matched the out-of-round tire to the rim. The vibration got a lot better so I'm pretty certain it's the tires, but it's still unacceptably bad. I left it with them again tonight with instructions to balance the tires for a 5th time (FIVE TIMES!), and for a tech to go drive it at highway speeds to see what I'm talking about.

I've also reached out to BFGoodrich to see if they will help with this. Right now, this is the last set of BFG tires I'll buy.

millball

I rekon that if the vibration started immediately after you changed the ride height, that might just be a big clue.

It would tell me that it wasn't the tires.

Did you happen to make any measurements before you made the changes???

ladybugRC

I have been workin on the same issue on my 4Runner since installing the 2" OME leaf springs. Been chasing this crazy vibration most pronounced at ~22 mph and it sounds like I'm going through the same checks as you. Checked the slip yoke, good u-joints, lots of fresh parts and I can't let go of the pinion angle as part of my problem. The other night I measured and I have only 2 degrees of difference between the transfer output and the rear end. I'm not sure if this is the problem, but if I were you I wouldn't rule it out just yet on your rig.

check out this video posted by another Yotatech member, Arlindsay.
I'm also glad I found your post because now I'm not so certain about my tires not being the problem. Let us know what your hear from BFG, if anything.

thezentree

I put new tires on it 4 or 5 miles after I finished the lift, and didn't break 40mph on the way to the tire shop. I've also replaced just about everything else that rotates, with the exception of the wheels and the front driveshaft, which wasn't vibrating before the lift, and didn't improve when I took the diff drop out. I changed a lot of things all at once, but I've gone through just about everything else that could be causing it.

I did get measurements before and after and while I don't have the exact numbers with me right now, I remember it being 3.5" in the front and 4.5"-ish in the rear.

thezentree

I will let you know what BFG says.

Tom Woods told me I should be good to go within 3° but I will keep this in mind if the tires don't solve it.

Acorn22

Yeah I'm running LX450 springs in the rear with 265/75's so quite a bit of lift and I bet my angle is well above the 3 degrees difference, however, I don't have a vibration anywhere with stock u-joints at 197k miles. So I believe the driveshaft can definitely handle the angle you're running at right now. I bet it is those tires! I won't buy BFGs anymore solely for that reason that you could get a bad batch that are impossible to balance.

ladybugRC

Have you tried coasting at speed in neutral to see if the vibration continues? I took a trip downhill and the vibration stopped when I disengaged the driveline. Easy way to possibly rule out the tires being the culprit.

4crawler has shims as low as 1 degree so I imagine it doesn't take too much for those u-joints to bind from being at the wrong angle.

thezentree

I've not tried coasting in neutral while in AWD, but in 2WD it doesn't make any difference.

I'm getting conflicting info on what an acceptable driveshaft angle is. Tom Woods emailed me and told me 3deg should be ok, and someone on Another board posted a link to a Spicer website saying that less than 1 degree is needed (but also said 3 degrees is ok?).

ladybugRC

Yeah, tell me about it. Like you said, finding good info on this topic is difficult. Even the 4crawler page doesn't give specifics on an acceptable pinion angle (that I can find, anyway). Perhaps it's just unique to each rig and the specific setup.

I'm likely going to go ahead with the 2 deg. shims since I've about ruled out everything else. May be a week or two to get the parts and do the install, but I'll let you know if it does the trick.

Keep us us posted on what you find out. Maybe we can solve this and save some others a headache in the future!

ladybugRC

Yeah, that would make me think tires are the problem... Try it in awd to be sure. I've started reading up on these tires. Seems that larger ones on 15" rims are particularly difficult to balance. What size wheels are you running? Could be a factor.

thezentree

Definitely the tires. I had them balanced for a fourth time today, and it's significantly better. Not fixed, but better. It feels like new cheap mud tires now instead of paddle tires.

BFGoodrich told me to talk to the tire dealer about runout specs. Such helpful, very assist. Wow. Definitely the last set of BFGs I'm going to buy.

Acorn22

Glad you got it figured out! Yeah those damn BFGs... Never know what you'll get from them now...