I got bad vibes, man- FIXED. Go to page 9

Jody Treadway said:
1) The output shaft of the TC is cut square Without a doubt
2) The output shaft bottoms out in the yoke Definitely
3) The taped hole is concentric and square with the output shaft Yup
4) The hole for mounting the yoke to the output shaft is concentric with the yoke 'Tis indeed my friend

With the yoke installed on the output shaft (no driveshaft), what's the run out? What's the run out with the driveshaft installed? Haven't checked yet. I plan to this afternoon when I get time.

I drove it to work today and paid close attention to everything. It's smooth as glass up to 50. Then you can just start to feel and hear the resonance begin. It gradually gets louder and more noticeable and from 56-60 is unbearable. At 61, it all but goes away. When it's doing it, you can feel the resonance in the e brake handle but not the transmission shifter. You *can* feel it a little in the transfer case shifter. It's bad enough to cause the image in the rear view mirror to be completely distorted. It really feels like driving on the rumble strips.

Tip in and tip out of throttle has no bearing on it. This absolutely rules out anything in the differential(s). Placing it in neutral doesn't change anything either. That essentially rules out driveline angle.

I'm really thinking it is something with the IRO adapter yoke. Maybe it's loose on the splines just enough under just the right load conditions to chatter.
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Dumb question but did you drill and tap the hole deep enough so that the bolt fully torques down on the yoke?
 
Jeff B said:
Explain?
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It's been my experience that if you have a marginal driveline angle issue that coasting in neutral will change the pitch/noise/sensation.

Let's say you have a pinion angle that is too high. It will generate noise and chatter on accel, but quieten down on decel.
Adversely, if the pinion angle is too low, it will tend to be fine under acceleration but growl under coast as the pinion angle naturally drops a few degrees.
Of course anything leaf sprung will react more so than something linked will.
 
Update
I pulled the IRO yoke off to cut it shorter. While it was off I decided to double check the depth of the hole I drilled and tapped in the output shaft. All good. Said why not chase the threads while it's out. Then I broke the freaking tap off in the shaft.
Chiseled it into pieces but had to cut 3/4" off the shaft to get to where the broken tap pieces were. Drilled out to 25/64 and installed a fresh Heli Coil.
Cut the yoke about 2" shorter and buttoned it up...
No annoying resonance remains. There are slight vibes from 55-58 but nothing I, er my wife, can't deal with.
It seems the Iron Rock yoke was loose enough on the shaft, side to side, and was moving on the shaft under certain driveline loads.
Weird, but fixed now!
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So...still doing it. 4 years later:flipoff2:. When I said "still vibes 55-58, nothing she can't deal with", that wasn't accurate. I don't blame her. It's annoying as heck to drive.
My wife uses her ZJ as a weekend bike hauler and the main highway it is driven on is speed limit 55. So it's right there in the speed range where it's most prevalent.
Recently installed a 231 case to rule out the hack n tap crap on the 242. I rebuilt it and added an Advance Adapters HD SYE kit. Had Oliver's make me a new front shaft (interchangeable with rear BTW). Test drove it, still has the same freaking vibration.
Not the transfer case. Not the driveshafts (been through 3 of them). Not pinion angle front or rear (I've adjusted them multiple times w/o any tangable change).
I'm beginning to wonder if it's something to do with the Spartan? I've had the rear diff back apart to verify bearings, setup and backlash and it's dead nuts good to go. I'm just not convinced it has anythiig to do with the locker as I have NEVER seen that happen before.
It feels like you're on smaller rumblestrips where you can see the rear view mirror vibrating. There is a general sense of roughness from 45 or so MPH and faster. Once you hit 55ish, it's bad.
I really am at a loss with it.
What say yinz?
 
Jody Treadway said:
ujoint front shafts. No wobble fronm rear shaft/calipers while on the lift. Tires been balanced a couple of times w/o any change.
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Is it getting the the vibration speed on the lift? What about something in the engine or transmission? What about pulling the spartan and throwing gears in there and see if it's still there? Or is the spartan a whole case locker?
 
ghost said:
Is it getting the the vibration speed on the lift? What about something in the engine or transmission? What about pulling the spartan and throwing gears in there and see if it's still there? Or is the spartan a whole case locker?
Click to expand...
that's my next move to remove the Spartan and retest.
 
Basic question...where is the vibe? Wheel? Seat? Both?

Will it present at an equal RPM different gear and speed?

Any chance its not drivetrain but some how cab mount or exhaust or engine mount related.
I know the 55-58 thing but grasping here
 
Ron said:
Basic question...where is the vibe? Wheel? Seat? Both?

Will it present at an equal RPM different gear and speed?

Any chance its not drivetrain but some how cab mount or exhaust or engine mount related.
I know the 55-58 thing but grasping here
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You feel it in your butt/seat/chassis. Steering wheel doesn't move.
Once at the road speed where it occurs, turning off OD has zero effect. So that rules out engine and transmission rotating assemblies
It's a unibody, so no cab mounts (good call though). Recently re-re-relocated the exhaust in the weird possibility it was hitting somewhere causing a resonance. I can't see anything remotely close to hitting at ride height or while "powerbraking".
 
I see the tires have been rotated and balanced, but have you tried a different set?

Duane
 
Jody Treadway said:
You feel it in your butt/seat/chassis. Steering wheel doesn't move.
Once at the road speed where it occurs, turning off OD has zero effect. So that rules out engine and transmission rotating assemblies
It's a unibody, so no cab mounts (good call though). Recently re-re-relocated the exhaust in the weird possibility it was hitting somewhere causing a resonance. I can't see anything remotely close to hitting at ride height or while "powerbraking".
Click to expand...
So then something is happening at 55mph regardless of RPM - if I understand?
While Im grasping...wet roads have any impact or what about driving in actual rain? (mentally chasing a wind tunnel harmonic thought)

Is it felt equally across enitre cab? IE both front and rear seats and not just a driver seat problem?
 
I dont know the problem but I do know the solution.

Get rid of it and buy Queen Lisa an Orange Urus


1660686609560.png
 
To @Ron point, could it be air/ aerodynamic forces? Or if it's her bike hauler, could it be harmonics/ pulses from wind going over bike mounts? (Assuming it's a roof mounted rack) just asking cause had a guy I worked with that installed aftermarket roof rack bars that just clamped into the door sill above the doors and he would get a similar issue. He never put the two together since it had been on there awhile before he ever hit the speed that would cause it and had me drive it and that's what I found out it was.
 
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