another day, another vibration...

[fishwater]

here's yet another vibration thread. and i (like most) am having trouble tracking down what's causing it. the posts i've read that sound very familiar to what i'm experiencing have no or very little follow-up. and believe me, i've read and re-read every vibration post on this site trying to figure out what to do next. i almost wish something would break or tear up, just so i would know what needed to be fixed!!

i'll start with background on my rig and then describe what she's doing.
here goes:

background:
-'96 with 210k
-OME 850/860 (~ 2.5" heavy/med) put on ~5 years ago
-new BFG A/T's 295's (balanced X 2 since purchased <1000 miles ago) (still have my BGF M/T 315's...)
-slee blue CC bushings with caster measured last week. Left side 2* and Right side 1.8*. this was after i installed the ARB and the M8000 winch, btw
-new U-joints in both shafts with zirks lined up correctly and both shafts balanced
-new front spindle bushings (<1000 miles ago)
-front knuckle service 3 weeks ago. bearings re-packed and in good shape. knuckle studs are torqued
-rear axle service last week with new bearings/lube, etc

description:
speed-specific vibration that usually starts around 60mph. the steering wheel will shake/shimmy as well as the front end (i feel it in the floor), it will cresendo then de-cresendo after about 2 minutes, regardless of changing speed. oftentimes, a rough patch in the road/hwy seems to bring it out or make the vibration/shake start, but not always. this "cycle" of vibrations occurs about every 5-10 min and it's been going on for about 4 months.

besides what's listed above, here's what i've done to date that hasn't had much of an effect:
-replaced all U-joints on the drive shafts and have them balanced
-pulled front and rear drive shafts one at a time using CDL w/o change (maybe a little worse when the rear is in)
-rotated and balanced new tires
-checked for loose connections on panhard, TRE's, control arms, frame/tranny mounts, shocks and nothing loose

any ideas of where to go next? like i said, i'm so sick of it i almost want something to break so at least i'll know what to fix!!
thanks,
blumer

[Romer]

Have you done an alignment? I see you had your castor measure, but did they check the Toe?

Does the vibration change if you brake lightly?

Have you do0ne a test run where you will shift to Nuetral when it occurs to see if this changes anything.

What about the viscous coupler,. I don't remember the specifics, but have you read up on those issues to see if its similar?

[knorrena]

How about checking your pinion nuts? I had a similar sound occur in my 70 when the rear nut worked its way loose. I could make it stop by playing with the throttle. I tightened it up and never heard it again.

Karl

[AJP]

Steering damper?? Did it happen before the new BFG tires were installed??

[fishwater]

Originally Posted by Romer

Have you done an alignment? I see you had your castor measure, but did they check the Toe?

Does the vibration change if you brake lightly?

Have you do0ne a test run where you will shift to Nuetral when it occurs to see if this changes anything.

What about the viscous coupler,. I don't remember the specifics, but have you read up on those issues to see if its similar?

romer,
toe measurement this last time was:
L toe 0.10
R toe 0.00
i have felt a vibration when i brake hard to a stop but i know my rotors are a little warped. i haven't noticed a change in the vibration i described above with light braking, but i haven't been paying much attention to that in particular and will on my way home today. what comes to mind when you ask that?
i've read up some on the viscous coupler but i do know that she wouldn't run with one shaft out unless i had the CDL switched on. not a real test, but i noticed it when i pulled one of the shafts out and forgot to hit the CDL switch.

Originally Posted by AJP

Steering damper?? Did it happen before the new BFG tires were installed??

the steering dampner was installed with the OME kit ~5 years ago. could be going out but i wouldn't think it would cause the vibration/shaking, it would just not be able to mask it as well.
and yes, it started before the 315 mud terrains were put on, but they certainly made it seem a lot worse. so i bought brand new 295 AT's and it's essentially unchanged.

thanks for the input!

[Romer]

On the brakes, just wondering if something with the rotor, pads, caliper or even a loose bolt on the caliper.

[Cruiserdrew]

It sounds like the start of Death Wobble, not a vibration. Try replacing your panhard bushings. Anything loose or not quite to spec can set it off. In my case, it was a bad upper panhard bushing.

Death Wobble can be hard to track down, but if your front end is tight and the suspension bushings are solid, it should not happen. I'm serious about the panhard bushings. They are simple to replace and if bad, allow differential movement between the steering box and the axle. That could easily lead to the oscillations of death wobble.

[uberhahn]

does the vibration continue if you shift to neutral at speed? Both tranny and transfer case?

[Beowulf]

Originally Posted by Cruiserdrew

It sounds like the start of Death Wobble, not a vibration. Try replacing your panhard bushings.

I agree with Andrew and while you are replacing the panhard bushings you may want to go ahead and get the adjustable panhard bars and get an alignment on a machine.

-B-

[landtank]

check your wheel bearings on the front axle. I wrote a procedure out there detailing how to do this. It might have made it to the FAQ section.

[NLXTACY]

http://forum.ih8mud.com/80-series-te...ation-faq.html

[fishwater]

Originally Posted by Cruiserdrew

It sounds like the start of Death Wobble, not a vibration. Try replacing your panhard bushings. Anything loose or not quite to spec can set it off. In my case, it was a bad upper panhard bushing.

Death Wobble can be hard to track down, but if your front end is tight and the suspension bushings are solid, it should not happen. I'm serious about the panhard bushings. They are simple to replace and if bad, allow differential movement between the steering box and the axle. That could easily lead to the oscillations of death wobble.

you're right, it's definitely a wobble. i might go with what b said and just replace it with the adjustable one and be done with it. so it's pretty simple to replace? i would assume with it out, something might relax a little and it might be difficult to get the bolts to line back up when you put the new one in (i.e. like using ratchet straps to get the the control arms back in?).

Originally Posted by uberhahn

does the vibration continue if you shift to neutral at speed? Both tranny and transfer case?

yes, it continues to shake when i shift into neutral at speed.

Originally Posted by landtank

check your wheel bearings on the front axle. I wrote a procedure out there detailing how to do this. It might have made it to the FAQ section.

yeah, that's a great write-up and i've used it a lot. thanks. couldn't feel any laxity in the bearings, but i've been back in there anyway to double check them and the preload and they've been fine. but i would figure after about 8-10k miles they would've siezed up if they were bad or not seated correctly...

thanks for all the feedback and i can promise you, there will be follow-up if/when i get this figured out.

[Beowulf]

Originally Posted by fishwater

it might be difficult to get the bolts to line back up when you put the new one in (i.e. like using ratchet straps to get the the control arms back in?).

I used a ratchet strap for installation and replaced F&R panhards with adjustables. The adjusting is the part that I didn't spend enough time doing. A few months later it was in for a final caster sweep after the Landtank plates and all the mods were finished. They were not adjusted correctly but the alignment guy made quick work for getting everything perfectly aligned.

He also used a ratchet strap... a big one.

-B-