Topic: Chasing down a highway-speed vibration

[andykrow]

Hi all,

I'm Hoping for some advice on where to go next with the vibration hunt. I don't think I am missing any of the obvious vibration culprits anymore.

The truck has a fairly deep vibration when on the gas between 55 and 65. It smooths out completely above 65, and it's gone when floating the throttle or decellerating. It's the worst around 60. (This is what I read on the speedo, corrected for the 35s and 529s I guess this is between 50-60.) It happens in all gears so does not seem to be RPM related. This isn't a higher pitched rattly sort of noise like a bad ujoint might do. I feel it more than I hear it.

The truck is an 85 4runner, 7" total lift (spring+shackles), dual cases, 35's. Over the last month or so I've been turning it into a bit more of a road trip machine and I'm trying to make it happy at highway speeds.

I am running a re-worked 84 front shaft in the back, it had the spline section and a ujoint replaced when it was gone over by a driveshaft shop about a month ago. They balanced it as well. Also have new 5.29 ARB diffs front and back. DS is clocked correctly, about .5 degree shy of the pinion flange being perpendicular with the driveshaft. Tires are 35 BFG mud KM2s with under 5k miles. Just had them balanced and rotated again in an effort to track this down, and the tire shop said no issues with balancing them at all. No play in the Tcase output shaft nor in the pinion flange.

I have not pulled the rear shaft and taken it up to highway speed, but I'm not sure that would help anyway. With this much lift that front DS will vibrate like hell at this speed. I guess that could be worth a shot.

Any other things to check out? What else could cause this? Worn motor or tcase mounts? I would think if those were an issue it would be tied to RPM and not speed.

I realize this setup is probably on the edge of something that can be highway friendly. Is there anyone out there with a similar rig that is smooth at these speeds?

Thanks in advance for any help you can give!

-Andy

[SqWADoosh]

Having the exact same problem with my rig right now. I'm pretty sure that mine is due to the fact that I lifted my transmission and cases with my Sky's cross member and they are contacting the body now. However I notice that we are both running 84/85 front shafts re-worked for the rear. I wonder if there is something with that shaft that is causing this?

[Dingman.]

The only time i ever experienced bad vibrations at that kind of speed while ON the throttle was with a bad u joint. 

After the round up when mike bent his rear driveline it vibrated the whole way home above 45-50, regardless if he was on the throttle or coasting.

[andykrow [OP]]

I have the sky crossmember as well but I'm not running any drivetrain lift so nothing is contacting the body. I did have to notch the horse collar to get the drive shaft to clear but there is a ton of space there now so no contact. The 84/85 shaft is very common for this application and I would think there would be a lot of info out there if it caused this issue.

I originally had an 8 degree shim in there, and went to a 10 to try to correct this. it maybe made it better but not a huge improvement. In any case the pinion angle is where it needs to be now, so that isn't the culprit.

I think the fact that it is only happening while on throttle and is not RPM dependent is telling me it's related to that driveshaft somehow.

I'll pull the shaft and get it up to speed in front wheel drive and see if I notice anything (other than my truck wanting to rattle apart from front vibes, haha)

It seems unlikely that the driveshaft place would have missed an issue with the CV end of the shaft, but anything is possible I guess. At this point I should have just bought a tom woods 

[blackdiamond]

Having the exact same problem with my rig right now. I'm pretty sure that mine is due to the fact that I lifted my transmission and cases with my Sky's cross member and they are contacting the body now. However I notice that we are both running 84/85 front shafts re-worked for the rear. I wonder if there is something with that shaft that is causing this?

If I was closer to you I'd let you bolt in my rear driveshaft and see if it make any difference.  Any chance your vibration is just getting amplifier to a level that feels concerning because of your heavy duty mounts?

[SqWADoosh]

If I was closer to you I'd let you bolt in my rear driveshaft and see if it make any difference.  Any chance your vibration is just getting amplifier to a level that feels concerning because of your heavy duty mounts?

I think it is a combination of that and the contact with the body due to the drive train lift.

[1985CRAWLER]

a drivetrain vibrating against the body feels alot different than a bad u-joint, a bad u-joint will feel similar to a out of balance driveline, if youve ever had one you will know right away.

it could just be the angle of the rear driveline,  7" lift is pretty tall, not saying the CV is maxed out but it could be close with that much lift

[andykrow [OP]]

Yeah... that's what I'm worried about. But, it's not crazy high, there must be other people out there with similar lift and dual cases.

I just checked and the angle the shaft is running at is 16 degrees relative to the output flange of the tcase. Anyone know if that's too steep to run smooth? And would an issue like that smooth out after a certain speed, or just get worse and worse?

Are there CV shafts out there that can run smooth at higher angles? I know there are high angle shafts but it seems to me that is just for preventing binding in super flexy rigs.

This vibe feels/sounds a lot like a loose pinion flange I had back in the day, although that would only happen while floating the throttle. Flanges on this rig are tight so that isn't the issue. The last bad ujoint I had made a chatter/rattle sound, less deep than this.

[blackdiamond]

Yeah... that's what I'm worried about. But, it's not crazy high, there must be other people out there with similar lift and dual cases.

I just checked and the angle the shaft is running at is 16 degrees relative to the output flange of the tcase. Anyone know if that's too steep to run smooth? And would an issue like that smooth out after a certain speed, or just get worse and worse?

Are there CV shafts out there that can run smooth at higher angles? I know there are high angle shafts but it seems to me that is just for preventing binding in super flexy rigs.

This vibe feels/sounds a lot like a loose pinion flange I had back in the day, although that would only happen while floating the throttle. Flanges on this rig are tight so that isn't the issue. The last bad ujoint I had made a chatter/rattle sound, less deep than this.

What is the difference in vertical hight from the floor between the two flanges?  If you measure to the bottom of the flange from the ground on a flat surface you can provide numbers that any of us can duplicate for comparison.

[andykrow [OP]]

I don't have a great way to measure this exactly right now other than a tape measure, so it isn't very exact. Difference in height between the flanges is just about 12". Flange-to-flange is roughly 39.5".

I do have an angle finder here and can measure the operating angle to be 16 degrees +/- 0.5 degree.

[blackdiamond]

I don't have a great way to measure this exactly right now other than a tape measure, so it isn't very exact. Difference in height between the flanges is just about 12". Flange-to-flange is roughly 39.5".

I do have an angle finder here and can measure the operating angle to be 16 degrees +/- 0.5 degree.

I would think that a tape measure should work just fine.  I thought was simply to get an idea of how your height compared to rigs with a similar wheelbase.

[Snowtoy]

Where are you feeling the vibrations, steering wheel, cab, or seat?  Where, will help narrow down the likely cause.

[andykrow [OP]]

I would say I am mainly feeling it through the seat. It can be heard but it is very deep. I can feel it a little through the steering wheels, but I do not think it is a front end issue. I've experienced front end vibes and they are generally far worse though the wheel.

I am out of town for the rest of the week, but I will pull the rear shaft when I get back and get it up to speed. I'm sure the front shaft will vibrate like hell but maybe it will be different enough that I can tell if the current vibe is gone?

My driveshaft guy can rebuild the cv end - two new ujoints and cv bearing - for $225 or so. With Toyota parts. He can also just build a completely new driveshaft with 1310 joints for around 450. Any advice on which of those is a better option? I already have about $350 into the shaft as it sits.

[daniresch]

I leaning towards the CV bearing being worn out. I had the same problem 5 months ago and was going crazy looking for what was causing my vibrations.
I replace all my rear U-joints, my wheel bearings, re-balanced and rotated my tires, all these things help.. but it wasn't until i replaced the CV bearing that the truck rode smoooooth again.

Do you have any experience with replacing u-joints? the parts are fairly cheap.
I'd recommend just replacing the CV bearing yourself if you can.

Part numbers:
Ujoint: Precision 513  ~$25
CV Bearing: Precision 614 ~$42

good luck!

[andykrow [OP]]

I haven't messed with ujoints before, would be willing to learn. My only concern is I don't have a press and I have seen a few things saying the cv end is difficult to deal with and the socket/hammer method really shouldn't be used.

As for the 513's, my driveshaft guy says he won't touch anything aftermarket for Toyota joints. He will only put Toyota joints in there. I also feel like I've read reports of 513's blowing up. Is that something to be concerned about?

[OVRAROK]

I have torn down and clearance my cv, did all the tearing down with hand tools and a vice

[Snowtoy]

Vibrations felt in the seat are almost always a drivetrain issue, u-joints, alignment issue between trans-drivleine-diff, bent out of balance driveline, trans mounts, etc, with the most common being from u-joints.

[andykrow [OP]]

Would worn mounts cause an issue while accelerating only? Is there a way to test the mounts? I have dual mounts on my crossmember and i don't want to throw that much money at it unless I can know for sure.

Thinking about how this vibe was not noted with the original shaft, and fixing pinion angle has helped but not cured it, the problem most likely lies in the cv section.

[OVRAROK]

after re-reading your first post, you state your DS is .5 degrees, are you referring to a 1/2 of a degree, this may be your problem, your rearend pinion shaft angle shoud be 2 degrees lower(pointing down) from your DS operating angle

[andykrow [OP]]

Yeah I mean 1/2 degree. I'm right now between 1/2 and 1 degree downward. (closer to 1/2) Which from everything I've read is perfect, and confirmed by a couple of sources. Ideally this angle is 0 degrees, but the downward angle is to account for axle wrap on acceleration.

I had an 8 degree shim in before so pinion was about 2.5 to 3 degrees downward. The vibe was still there, on acceleration. My understanding is if the pinion is pointed too far down any vibes related to pinion angle will be on deceleration.

Anyway, putting the 10 degree in there helped a little, I think. The difference was subtle. But I wouldn't want to run anything steeper than that.

[OVRAROK]

when I had my rear DS built by high angle DS, I spoke to the owner about rear shaft angles, he was the one that advised me to set at 2 degrees, have you had anybody stand next to truck and look at pinion angle when you take off, ideally you want it line up under load, I know with ladder bars you set at 1/2 degree, I would think with leafs you would need more then that

[andykrow [OP]]

I definitely need to take a look under there while someone starts it moving. Maybe this thing has terrible axle wrap and I had no idea, haha.

[Tjcarter]

jack the rear wheels off the ground, turn the truck on and put it in gear. Have someone give it gas and watch the driveshaft to ensure it's not bent at all... you wont need to push it to 55-60mph to notice a wabble or vibration. You will likely see it quckly if it's bent or not straight, or if you have a bad joint- it should be easy to diagnose. I had the exact same thing on my rig and it took me actually watching the shaft move before i found it was slightly bent.  I'd only feel the vibration at a higher speed, then it'd taper off as i went faster. Weird. That's what i found though...

[Bananaclip]

I had this issue 2 different times. First it was an unbalanced drive shaft.  Second time it was a joint going bad.