Harmonics (and alignment woes) (danger: long and frustrating)

[hobbes]

About three months ago I purchased and had installed a set of 285 Revos. I had no problems with the Cruiser (including a long highway trip). The next month I installed a 2.5" OME medium lift plus shocks and caster correction bushings. Some where in there, I believe after I installed the lift, I picked up a nasty harmonic sound (with small vibration). It starts at 55 mph and continues up through about 75 mph, then generally tapers off. It's very annoying. I took the truck to another shop and had the tires rebalanced since the first shop wouldn't stand by their work. It was a bit better, but still there and annoying. So I took the truck back about a month later. They rebalanced the tires and now it was worse. (At the same time I installed front and rear CDan U-joints to eliminate any chance of it being the driveshafts). Later that week I had to take a 12 hour trip and return the next day. Man, talk about a bad headache when the day was done. Frustrated, I looked into the "road force" balancers Doug mentioned in his post. A couple calls and a local Merchant Tire said they tackle the job for only $9 per tire which was $15 per tire cheaper than anyone else. While there I decided to knock out an alignment as well. It took awhile because the tech said they were having a hard time getting the alignment set (hard to turn the rods). My Cruiser is very clean and I've never had a problem doing anything under the truck due to rust. Heck, even my rear lower shock bolts look nice. Well, I got the truck back and it pulled a bit to the left. I took it out on the highway and no change in the harmonics. I can feel a slight vibration (that feels exactly like tire vibration) starting at 55mph, but the accoustic harmonics are still annoying loud. To make matters worse, now almost every time I do a tight turn slowly to the left I hear a pop from the left front of the truck. I've been dealing with this stuff for 3 straight months now, and am getting pissed. The truck has about 100k miles on it. I've only got about a year on all new bearings up front and a birf repack. The birfs both looked fine when I repacked them.

Has anyone ever run into a harmonic problem after a OME 2.5 suspension lift? I was sure to re-install the rubber bushings on top of the springs. Just to complicate matters I can hear the same tone as the harmonic tone when I go over bumps. Clear as mud? The truck seems to drive fine other than what I've mentioned.

How in the heck can someone aligning the truck cause the popping when I turn? I know my birfs are greased. Plus the occurance exactly started with me picking up my truck from the alignment.

Just to finish ticking me off, the shop kept my lug socket as well.

I'm taking the truck back tomorrow for the alignment and popping, but I'm hoping to give them the answer to my problems since I have no confidence in their work. Does anyone have any ideas?

My post alignment specs are: Camber (L/R): .3/.1. Caster (L/R): 1.6,/1.9. Toe (L/R): 0.08/0.12. (The caster is out, but not by much.)

Thanks for any help. I'm reading to drive the thing into a wall I'm so frustrated.

 

[Rich]

Before you were reporting a vibration problem that only occurred with power on, is this still the case? If it is, then I think you have a driveline problem - driveshafts, tranny, transfer case, or diffs.

To rule out wheel & tires, swap them from front to back and see if the problem changes. If it does, then replace one tire on the bad axle with the spare and see if it changes again. If it does, then you have identified the tire or wheel that is bad.

If that fails to identify the problem, then I suggest that you put your stock springs back in and see if that relieves the problem. If it does, then you most likely have driveline angle problems.

 

[IdahoDoug]

Tell me about the "Somewhere in there..." part of your post. Why can't you pin down when this happened? Did you install the lift and by unlucky coincidence you didn't drive on the highway for a few weeks? Did you go wheeling in there somewhere?

I ask this because I believe you are well attuned to this vehicle and I feel your frustration in not being able to pin it down. You are not being too picky. You are not insane. It's a mechanical device and there's a source.

Before I have you driving down the road with sections of garden hose duct taped to various components and run in the windows, tell me about the "Somewhere in there...". Give it your best shot.

DougM

 

[hobbes]

Rich, good memory. I pulled the front drive shaft after that post. The harmonic noise decreased...but not by much. It seemed to me to be more of a case with the front drive shaft out there was one less means of vibration transferal, if that makes any sense. I will note that with the front drive shaft out, the gear selector and transfer case shifter moved more. Specifically, the transfer case shifter moved to the right under accleration. I looked at the mount when I was putting back in the front drive shaft, and it looked fine. The harmonic noise is now definately power on or off (or even in neutral). When I made the comment about the power on/off, the harmonic sound was at a minimum.

Doug - "some where in there" is between the time I last had the truck on the highway without the OME lift and the first time with. I can go extended periods without hitting the highway (and indeed did). The time period was about three weeks during which nothing transpired (off roading, accidents, ect) other than the OME install. I do really notice tire balance now after owning a Cummins (it would pitch weights and spin the tires on the rims (which the tire dealer claimed was not happening until I made him mark everyting and drive down the street)). Even the passenger seat alert system comments on the noise right now.

The thing that has me scratching my head (besides the popping from the front wheel), is the sound as I go over bumps. The truck doesn't give a "solid" sound. It's more of a "hallow" sound. I was thinking maybe a shock or something. I couldn't get an air gun on the driver's top shock mount, but it seems snug.

Thanks for the help guys.

 

[sleeoffroad]

Is the noise a vibration type that comes and goes with RMP's/driveline speed? Does it change when you are on the throttle or not?


Did you install the suspension yourself? Did you seat the washers for the shocks properly in the holes ? Did you tighten the control arms bolts with truck at ride height? Most suspension install related noises are banging and clancking when driving on dirt roads or turning. Noises that are related to speed are probably drivetrain.

When last did you grease the U joints? It could be in the transfercase> It could be in the diffs.. Easiest way is to remove one driveshaft at a time and drive it. Make sure to lock the center diff. 99% of the time it is bad u joints that now operate at a different angle due to the lift.

Extreme meausre, swap oem springs back in and see if it goes away. Or load 400 lbs in the back and see if it changes.

 

[hobbes]

Christo,

It is strictly a function of speed. Not power, gear, or RPM. I installed the suspension myself. I think I did it correctly. The suspension was hanging. What symptoms does that manifest.

All Ujoints are new.

Thanks....

EDIT: I said I didn't tighten the control arms with the weight on the truck, but now that I think about it I did.

 

[hobbes]

Okay, I think the shop got the popping noise. They had the tie rod clamp hitting the radius arm. You could see the marks on the tie rod clamp bolt. They ran out of daylight and didn't check the balance on the tires. I'll have them do that over the next couple days as work allows. Pending those results, I'll start pulling and re-installing each of the shocks to make sure those are correct. Then I guess I'll try the springs. After that I'll pull the rear drive shaft (since I've tried pulling the front and gotten no change).

Thanks...

 

[semlin]

I think you are doing a good job of systematically tracking this hobbes, and I hope you find it. only comment: are you 100% sure it is not an exhaust whine? I have just changed my cats and I have a new exhaust whine today at 30-40 mph that is annoying. It sounds a lot like a drivetrain whine in the rear. The classic place to get the exhaust "whistle" is 60-75 mph which is close to your problem. I had that for a while until I crushed the end of my exhaust pipe.

 

[hobbes]

semlin,

It's not the exhaust (at least it doesn't seem to be). I'd think that would vary wtih RPM. I pulled the spare off today since I had raised it in that time frame. I thought maybe it could be rattling, but no difference.

Thanks...

 

[hobbes]

Okay, back to the top with this. I still have the harmonics starting at 55mph. I've since rotated my spare tire through every station and removed the rear drive shaft. I think removing the drive shaft reduced the harmonics a bit, but it's still there. Power on, power off, while braking, etc. Since it was reduced a bit by removing the rear shaft, I'm wondering if I should just get it balanced while its off. I fear that could just be a waste of money.

Unfortunately, I threw out my old suspension pieces when I put on the OME. My next plan is to try putting the rubber factory shock bushings on the OME shocks to see if that helps. Does anyone know if you can just order the shock bushings, or does Mr T make you buy the entire shock? I thought I read about it on here a month or two ago, but I cannot find it now. Search seems to be working "funny"....

 

[semlin]

This is coming from the back, correct, or is there another reason you haven't tried dropping the front shaft? Assuming it's the back, you have apparently eliminated a rear driveshaft cause, so why don't you repack or replace your rear wheel bearings? I know this seems to coincide with the suspension change but I have a hard time envisaging the OME bushings being the problem (assuming you torqued them properly). I think that you should eliminate the more likely culprits first and a rear axle service is worth doing anyway imho.

 

[sleeoffroad]

OK, you say your birfields are greased. When last did you do a wheel bearing repack and tighten? You are running bigger tires, so a loose wheelbearing could be accentuated. Also try to borrow a set of stock wheels with Michelin tires and see if that changes.

I doubt if bushings is going to change a speed related vibration and sound.

 

[hobbes]

Semlin - I did pull the front drive shaft earlier and got the same results as the rear drive shaft. It reduced, but not significantly. That lead me down the path to change out all the u-joints to no avail. I thought about the mis-torquing of a shock bushing and pulled and re-installed every shock with no change. Edit: I touch on the rear bearings below...

Christo - I've been thinking about the wheel bearings as well. I'll start by saying I've had every tire in the air and given a good pull on the top and bottom of the tire. There is no movement on any wheel. With that said, when I bought the truck aobut 10k miles ago the front end had a "roar". I could tell from the test drive that the front bearings were toast. Right after I bought the truck, I serviced the front axle with all CDan parts (except the Timkens which I sourced locally). The front knuckles were about what I expected to see. Nothing too bad, just replaced the seals and re-greased EXCEPT for the bearings. Both the bearings and races were toast. Everything went back together smoothly except for struggling with the bearing pre-load. I never could get the "pull force" down to the factory setting even after completely loosening the hub nut (yes, I "set" the hub with the factory torque level to seat it). I chalk it up to the heavy-ish grease that I used (Valvoline fully syn wheel grease, which btw is what I used on the birfs). I had the on duty mechanic at the garage check it out prior to putting the wheel back on, and he agreed with my results. I have never serviced the rear bearings as I don't have the special tool. I thought it was a couple hundred bucks to buy (that may be wrong). The rear wheels, again, show no movement when pulled top to bottom and there is no visible leaking fluid anywhere. I can't help but think "bearings" sometimes when I hit a bump in the road just right and I feel a slight buzz in the truck. In summary, I've got 10k on a birf/front bearing job where the bearings and races were shot. I have not touched the rears. Can you get a slight vib from rear bearings between 55-75 mph? Could I be getting that "hollow" sound from that when I hit bumps and still not be able to detect any tire movement when the truck is in the air?

Thanks....

 

[sleeoffroad]

I would do the rear bearings. Search for thread on making rear SST toolk yourself. Also, did you do the trunion bearings when you did the front wheel service?

Also, did you have someone with wheel bearing setting experience check the pre-load by feel? I know this goes against the book, but there are a lot of variable and if you say that you had trouble setting it by the book, you might have left them too loose. It is one thing to do it by the book, and another to have the experience to know when it is done right.


One other thing, shooting in the dark here, but pull both front and rear shaft at the transfercase and grab each flange and see if you can rotate them in opposite directions. Remote possibility is a viscous coupler that is starting to go and you are experiencing drivetrain bind up. Shot in the dark, but worth checking.

 

[hobbes]

Christo - I'll look into making the SST. I did replace the trunion and races as preventative maintenance when I was in there. I did have someone check the pre-load by feel that was a "professional" mechanic. But what if we got it wrong? Since I was trying to get the "factory numbers" and was failing on the high side, if I erred I'd bet it would be on the loose side of the actual setup. Would loose bearings not show up in the standard "pull the top and bottom of the tire test"?

Thanks....

 

[hobbes]

Well I've now replaced the rear bearings, the fronts seem good, and I just had the tires re-checked on a "road force" machine (I couldn't find anyone with a set of tires to swap out). I guess the next thing I'll try is to have both drive shafts balanced since I'm running out of ideas. While I have them off I'll do the viscous coupler check.

 

[Arya Ebrahimi]

Hobbes, sorry to hear of all your troubles. I saw you driving down Great Neck road two weekends ago and was admiring your truck as it passed(I was at the Citgo balancing my tires). Nothing to contribute, just sayin hi ;p

 

[hobbes]

Arya,

Wish I had known that. I would have tried to grab your tires for a quick spin. Oh well. Thought I saw you near the Chix restaurant the other week. I saw a Cruiser running a Kaymar rear bumper around here the other week. Looked nice.

 

[Arya Ebrahimi]

I think you had the with you. I wasn't in a position to lend you the tires anyway, my buddy came in on a Sunday for 20 mins to let me balance my tires. He had actually left a pool party to help me out, so it wouldn't have been the ideal time to lend you my tires

My parents actually moved out of the area last weekend, but I'll be in town this weekend. Don't know who's got the Kaymar rear bumper. It's definately not me(unfortunately).