On a Mission: 50mph rumble

[SAString]

Have you tried it without the wheel spacers ?
You do know that any slight amount of off balance could be it

The same rumble/vibration was there before the spacers. Before the lift also. I have to put trust into the new parts and professionals that balance my tires, driveshafts, do alignments etc. I've replaced and balanced so many parts, that now I think any one of then could be bad and I'd never know.

I've already removed the spacers in the front, due to rubbing issues, but could remove the rears and go for a drive, when the weather improves.

 

[SAString]

VIBRATION SOLVED!

After going through and inspecting everything over again, with numerous test drives and configurations, Dial indicator run-outs on the yokes indicated nothing bent. So, I narrowed it down to the drive shaft AGAIN! I took the original shaft into Inland Truck Parts in Olathe, Kansas and had it balanced after my first set of new u-joints. That didn't solve it. I then switched to Spicer sealed u-joints, that didn't fix it. I went back to Inland for the balance again. Ended up buying a WHOLE NEW custom shaft with new spline yoke and a shiny new harmonic disk. THAT made it worse! I didn't see any weights this time, so I was suspicious. Then I read there was a Jeeper guy named Ron Istas at the Missouri Inland Truck facility. I called Ron and made an appointment, telling him I was suspicious of what the Kansas store had done. Ron drove it, felt the harmonic and had me pull the shaft. He and his team put it on the balance machine (Fantastic facility) and spun it up to high RPM. It was well within tolerance, they even tacked on a small weight to make it perfect. I reinstalled it and Ron drove it again. No improvement. So after a lot of thought, Ron said, "it's got to be that big harmonic balance disc causing a frequency to set-up at 50mph. Pull it off this weekend and see if it helps".

Yesterday, I pulled the shaft and precisely knocked off the disc with a BFH, reinstalled the shaft and went for a drive. IT'S GONE! No vibes at 45-55 even under acceleration! All this work and money and that's all I really needed to do. REMOVE SOMETHING, not add a new everything! Again, Ironic that something intended to reduce vibrations was actually causing them.

 

[ltd02]

Excellent! Quite the route to success but at least you got there. I'll definitely have to keep this in mind if my vibe gets worse or annoys me enough. Mine is still pretty subtle.

I did get mine up in the air and took a real good look at my U-joints and they look great close up and feel nice and tight. No binding and not even a speck of rust on them.

 

[tommudd]

Excellent! Quite the route to success but at least you got there. I'll definitely have to keep this in mind if my vibe gets worse or annoys me enough. Mine is still pretty subtle.

I did get mine up in the air and took a real good look at my U-joints and they look great close up and feel nice and tight. No binding and not even a speck of rust on them.

On my 04 the rear ujoints looked and felt the same, looked good, felt tight, when I pulled them apart, all rusted inside , that was at 55,000 miles, 38,000 lifted miles

 

[tommudd]

VIBRATION SOLVED!

After going through and inspecting everything over again, with numerous test drives and configurations, Dial indicator run-outs on the yokes indicated nothing bent. So, I narrowed it down to the drive shaft AGAIN! I took the original shaft into Inland Truck Parts in Olathe, Kansas and had it balanced after my first set of new u-joints. That didn't solve it. I then switched to Spicer sealed u-joints, that didn't fix it. I went back to Inland for the balance again. Ended up buying a WHOLE NEW custom shaft with new spline yoke and a shiny new harmonic disk. THAT made it worse! I didn't see any weights this time, so I was suspicious. Then I read there was a Jeeper guy named Ron Istas at the Missouri Inland Truck facility. I called Ron and made an appointment, telling him I was suspicious of what the Kansas store had done. Ron drove it, felt the harmonic and had me pull the shaft. He and his team put it on the balance machine (Fantastic facility) and spun it up to high RPM. It was well within tolerance, they even tacked on a small weight to make it perfect. I reinstalled it and Ron drove it again. No improvement. So after a lot of thought, Ron said, "it's got to be that big harmonic balance disc causing a frequency to set-up at 50mph. Pull it off this weekend and see if it helps".

Yesterday, I pulled the shaft and precisely knocked of the disc with a BFH, reinstalled the shaft and went for a drive. IT'S GONE! No vibes at 45-55 even under acceleration! All this work and money and that's all I really needed to do. REMOVE SOMETHING, not add a new everything! Again, Ironic that something intended to reduce vibrations was actually causing them.

See, many want to keep throwing a lot of new parts at something that doesn't need new parts

 

[ltd02]

On my 04 the rear ujoints looked and felt the same, looked good, felt tight, when I pulled them apart, all rusted inside , that was at 55,000 miles, 38,000 lifted miles

Mines gonna have to get a whole lot worse before I worry about changing mine. Not hard to do but since its been like this for so long I doubt it is related to anything actively degrading. I've driven a few vehicles with wonky U-joints and my symptoms are nothing too bad, yet... :gr_grin:

 

[SAString]

See, many want to keep throwing a lot of new parts at something that doesn't need new parts

Well, it's been almost a year. I replaced a lot of dying systems and aging parts, plus I learned a lot about the KJ while doing it. I know my jeep is much happier and reliable now. You know, despite all the work, it was kinda fun!

Sort of sounds like I'm gunna stop working on it.........:happy175:

Hopefully my efforts documented in this thread will help someone else.

 

[duderz7]

I might try removing mine if I'm bored one day. Glad you figured it out!

 

[a_ibrahem]

very interesting thread, really admire your fighting spirit

I Have the similar vibration on GAS but at any speed
today i replaced rear u-joints with spicer sealed ones non-greaseable
vibration got much better but around 100-120 Kmh its there

curious how did you remove that harmonic balance heavy thing ?

Br,
Ahmed

 

[TomB985]

Can you post a photo of the part you're talking about?

 

[a_ibrahem]

I'm talking about the big harmonic balancer disc on the rear drive shaft

Don't have a pic

Regards,
Ahmed
KJ 2007

 

[SAString]

Attached is a pic of the shaft with the disc off. Best to have the shaft cold and lightly heat the disc with a blow torch. With the spine end on some wood, lightly tap the disc as close the yoke as you can with a hammer. I used a long 3/4" socket set upright on the disc and tapped that all around until the disc dropped off.

This worked for me but may not solve your issues. My vibes are not entirely gone (now I'm sensitized to every little unexpected frequency). I believe the heavy weight was exaggerating the amplitude of my driveline frequency at 50mph. I'm fairly sure the entire driveline sets-off a harmonic frequency because my engine mounts and trans mount are old and worn (134k mi). I'm looking forward to my results following their replacement (but not work itself!)

 

[a_ibrahem]

Attached is a pic of the shaft with the disc off. Best to have the shaft cold and lightly heat the disc with a blow torch. With the spine end on some wood, lightly tap the disc as close the yoke as you can with a hammer. I used a long 3/4" socket set upright on the disc and tapped that all around until the disc dropped off.

This worked for me but may not solve your issues. My vibes are not entirely gone (now I'm sensitized to every little unexpected frequency). I believe the heavy weight was exaggerating the amplitude of my driveline frequency at 50mph. I'm fairly sure the entire driveline sets-off a harmonic frequency because my engine mounts and trans mount are old and worn (134k mi). I'm looking forward to my results following their replacement (but not work itself!)

Thanks lot,
My KJ has 250Km now, before replacement of u joints it was vibrating badly, now only starting 100km/h and above I tried to make the mechanic keep shaft in same orientation as it was and he says he did but I'm not so sure

If I remove that harmonic disc it can be installed again ?

Br,
Ahmed



Regards,
Ahmed
KJ 2007

 

[SAString]

Thanks lot,
My KJ has 250Km now, before replacement of u joints it was vibrating badly, now only starting 100km/h and above I tried to make the mechanic keep shaft in same orientation as it was and he says he did but I'm not so sure

If I remove that harmonic disc it can be installed again ?

Br,
Ahmed



Regards,
Ahmed
KJ 2007

Hi Ahmed:
Yes as long as you don't damage it in the process. Maybe mark the shaft and weight so they go back together the same. It would be a good idea to have the shaft balanced again at a good shop, if you feel you need to re-install it. For me, the weight is vibrating up and down. All that weight is transferring into the Jeep. So, less weight moving, less transferring to my seat! I get a smaller vibration now at a higher frequency at about 55mph, so much more tolerable. I'm changing the motor mounts now. Will report later.

 

[tommudd]

:blah:

 

[SAString]

Mission Accomplished

I thought I would give an update on my vibration elimination endeavors. I've spent part of my holiday off-time replacing my Jeep's transmission and motor mounts. All three mounts were badly cracked and compressed. It seems the engine/transmission/transfer case were vibrating as a unit, doing a 50mph harmonic dance and tossing around that big balance ring on the end of the drive shaft! Removing the ring helped the transfer of vibrating weight into the shaft, but that wasn't the cause. Now that the engine and trans are dampened and still, the Jeep is smooth and vibe free! Mission Accomplished!
arty36:

 

[ltd02]

Now you've got me thinking I should check mine.

 

[a_ibrahem]

Removed the harmonic balancer and still vibrating on acceleration around 100 km/hr

Engine mounts are good

Can it be front shaft ?

Heard something about transfer case bearings ,any one have experience with that ?

Thanks in advance guys

Regards,
Ahmed

Regards,
Ahmed
KJ 2007

 

[SAString]

Removed the harmonic balancer and still vibrating on acceleration around 100 km/hr

Engine mounts are good

Can it be front shaft ?

Heard something about transfer case bearings ,any one have experience with that ?

Thanks in advance guys

Regards,
Ahmed

Regards,
Ahmed
KJ 2007

Hi Ahmed: I can't tell, but are you lifted? With the balance weight removed, You can see that the drive shaft looks too short and the Transfer case output shaft looks to long. That geometry is going to vibrate, even with a perfectly balanced shaft (I even tried the JBA Y-link extender to improve the angles to no avail). Just the nature of the beast. If I had the money, I would have bought a slip yoke eliminator (SYE) kit and a new matching drive shaft. That would solve most of it and would be my advice.

Good luck.

 

[tommudd]

Hi Ahmed: I can't tell, but are you lifted? With the balance weight removed, You can see that the drive shaft looks too short and the Transfer case output shaft looks to long. That geometry is going to vibrate, even with a perfectly balanced shaft (I even tried the JBA Y-link extender to improve the angles to no avail). Just the nature of the beast. If I had the money, I would have bought a slip yoke eliminator (SYE) kit and a new matching drive shaft. That would solve most of it and would be my advice.

Good luck.

No it is not the nature of the beast, sorry but many are running with zero vibes at all , trust me. Only a very few do and its hard to say why when you're 1000 miles away and can't drive/ check it out