Vibrations

[Larry221]

Hey all I have a 97 tj with a tummy tuck and long arm lift it has a sye and cv shafts. The lift wasn’t done by me or any of the work. I bought it like this. Very clean build. BUT. Since owning it since Feb 22 I’ve put 20k on it.

I have a vibration when I got it and it’s progressively getting worse. It starts on accelerating and when in lock up low rpm under 2k around 40 all the way to 70mph. @3000rpm in drive it is the worse. I can feel some vibes at idle. The vibe I’m getting is more harmonic/bassy/rumble strip feeling.

Lmk what your thoughts are. I’m guessing mounts ? But it does it in decel too?

 

[Jerry Bransford]

Could be that someone replaced the Mopar motor mounts that have good quality rubber bushings with aftermarket motor mounts with polyurethane or cheap stiff rubber bushings. Same possibility with the transmission mount, it should be rubber but some clueless types convert to polyurethane thinking it's better... it's not.

 

[Larry221]

Could be that someone replaced the Mopar motor mounts that have good quality rubber bushings with aftermarket motor mounts with polyurethane or cheap stiff rubber bushings. Same possibility with the transmission mount, it should be rubber but some clueless types convert to polyurethane thinking it's better... it's not.

I checked them out they look stock. No play with pry bar. Checked trans mounts. The front splines on the front Adams driveshaft had lots of play. Dropped it off for rebuild and still vibrating. Does it on accel and cruising. When I let off it vibes for a little till about 30. When on the highway it’s buzzing the dash and the mirrors get fuzzy. I’ mechanically included but this is stumping me. Does my shaft angle look ok?

 

[Larry221]

Bump

 

[Hazegray]

I would highly recommend getting the Klein digital angle finder, typically found in the big box home improvement stores. Eliminates the guess work on setting driveline angles.

 

[Larry221]

My drive shaft angle is .5 under the pinion angle. How does this trans mount look? Toast. Could that be why it’s vibrating?

 

[John Middleton]

Could be that someone replaced the Mopar motor mounts that have good quality rubber bushings with aftermarket motor mounts with polyurethane or cheap stiff rubber bushings. Same possibility with the transmission mount, it should be rubber but some clueless types convert to polyurethane thinking it's better... it's not.

Fighting harmonic vibration for over a year. 03 Rubicon. 3.5 MC short arm. Ucf mid TT. Rear Adams DS & rebuilt & balanced Front DS. Can unhook either (F/R) DS & vibe goes away. Had mechanic lift it today & says my tranny mount is cracked. This is a Mopar oem mount placed Jan 2021. Less than 10K on it. Wondering what to replace it with!

 

[eastbloc]

Fighting harmonic vibration for over a year. 03 Rubicon. 3.5 MC short arm. Ucf mid TT. Rear Adams DS & rebuilt & balanced Front DS. Can unhook either (F/R) DS & vibe goes away. Had mechanic lift it today & says my tranny mount is cracked. This is a Mopar oem mount placed Jan 2021. Less than 10K on it. Wondering what to replace it with!

Find another rubber one. As far as harmonics, i will confidently bet that tranny mount is not the source and not the solution.

 

[Jerry Bransford]

Fighting harmonic vibration for over a year. 03 Rubicon. 3.5 MC short arm. Ucf mid TT. Rear Adams DS & rebuilt & balanced Front DS. Can unhook either (F/R) DS & vibe goes away. Had mechanic lift it today & says my tranny mount is cracked. This is a Mopar oem mount placed Jan 2021. Less than 10K on it. Wondering what to replace it with!

Stay Mopar, perhaps you got a counterfeit before. What axle ratio? Lower ratios like 4.88 can cause hard to troubleshoot vibrations. Sometimes it's a bad transfer case vibration damper.

 

[AndyG]

Fighting harmonic vibration for over a year. 03 Rubicon. 3.5 MC short arm. Ucf mid TT. Rear Adams DS & rebuilt & balanced Front DS. Can unhook either (F/R) DS & vibe goes away. Had mechanic lift it today & says my tranny mount is cracked. This is a Mopar oem mount placed Jan 2021. Less than 10K on it. Wondering what to replace it with!

Wonder why the mount failed so soon ?


If unhooking either doesn’t do the trick, i’d start with unbolting the rear at the output and rotate 90 then 180 degrees and see if it changes, and talk to Adams.

 

[John Cooper]

I had harmonic vibrations, then I realized I had a Beach Boys CD in and it was playing good vibrations.

Sorry couldn't resist!!

 

[John Middleton]

Jerry, how do I check tcase damper?
So, i previously sent rear DS back to Adams to check. Unbolted both so many times I’m sure I’ve clocked 180*. Gonna try OReily tranny mount. Any suggestions on other brands? not sure why Mopar failed ! My Motor mounts are Mopar w 1” solid blocks & less than one year old.staying Away from poly.
I also talked to UCF about their tranny mount but it’s less rubber than oem!

 

[Jerry Bransford]

Jerry, how do I check tcase damper?
So, i previously sent rear DS back to Adams to check. Unbolted both so many times I’m sure I’ve clocked 180*. Gonna try OReily tranny mount. Any suggestions on other brands? not sure why Mopar failed ! My Motor mounts are Mopar w 1” solid blocks & less than one year old.staying Away from poly.
I also talked to UCF about their tranny mount but it’s less rubber than oem!

What's a tcase damper? Are you waiting until the skidplate is bolted up and the wheels are on the ground before tightening the four nuts holding the transmission mount to the skidplate? Its mounting holes are slotted and allow fore-aft positioning of the mount so it could have been tightened in the wrong position before which stressed it enough to break it once the tires were on the ground.

 

[John Middleton]

Harmonic balancer wheel hanging off the TCase output shaft that the rear ds bolts to.
Jerry, you may be right regarding keeping tranny mount bolts loose till it’s off the lift. Don’t think I did that!

 

[Jerry Bransford]

Harmonic balancer wheel hanging off the TCase output shaft that the rear ds bolts to.
Jerry, you may be right regarding keeping tranny mount bolts loose till it’s off the lift. Don’t think I did that!

Great, the mount will position itself fore/aft to where it wants to be once the tcase skidplate is bolted into place and the Jeep is sitting with all its weight on the tires. Then tighten its four nuts.

 

[SHAKEY]

You never said what dif. ratio you are running. 04 Rubi 4 1/2" lift w 5.13 had the same problem. dumped thousands of $ for over a year and a half with no joy. Replaced drive shafts with Woods, no change .Raised / lowered T case Etc. Rebuilt front diff because of failed pinion brg from vibration.. Had drive shafts re-balanced, no Change. Rebuilt Xfer case, front out put bearing was worn from vibrating. Stumbled upon a you tube video on European drive shaft balancing machines that are capable of 10,000 rpm used on manufacturing machinery. Watched you tubes on drive shaft builders and all of the big time builders only balance to 3,000 rpm MAX. I called several BIG name builders and none had the capability to balance over 3,000 rpm. With my 5.13s with 35" tires I am turning over 3500 shaft rpm at 70+ mph although vibration starts at 55 and progressively got worse as speed increased. Denny's Driveshaft in Kenmore, New York is the only shop I found in the US that can and will balance a shaft to 10,000 rpm. I ordered a new shaft and requested it balanced to 6,500 rpm. I installed and no vibration up to 90+ mph. The imbalance is in the double carden joint center section angle due to cardin joint angle. You will never get a good front drive shaft angle because the front Xfer case shaft is tilted up and the pinion angle is horizontal or pointed down to get a caster angle + 4 or 5*. I have since installed The Yukon free wheel hub disconnects to eliminate the need to ever have to worry about drive shaft balance and to give me the option of 2 wd low range. Just like my CJ in high range my TJ will roll very easily on level ground and rapidly pick up speed on down hills with no throttle input and require downshift or using brakes to maintain speed.
Just my experience with TJ drive line vibrations.

 

[eastbloc]

You never said what dif. ratio you are running. 04 Rubi w 5.13 had the same problem. dumped thousands of $ for over a year and a half with no joy. Replaced drive shafts with Woods, no change .Raised / lowered T case Etc. Rebuilt front diff because of failed pinion brg from vibration.. Had drive shafts re-balanced, no Change. Rebuilt Xfer case, front out put bearing was worn from vibrating. Stumbled upon a you tube video on European drive shaft balancing machines that are capable of 10,000 rpm used on manufacturing machinery and drag cars. Watched you tubes on drive shaft builders and all of the big time builders only balance to 3,000 rpm MAX. I called several BIG name builders and none had the capability to balance over 3,000 rpm. With my 5.13s with 35" tires I am turning over 3500 shaft rpm at 70+ mph although vibration starts at 55 and progressively got worse as speed increased. Denny's Driveshaft in Kenmore, New York is the only shop I found in the US that can and will balance a shaft to 10,000 rpm. I ordered a new shaft and requested it balanced to 6,500 rpm. I installed and no vibration up to 90+ mph. The imbalance is in the double carden joint center section angle due to cardin joint angle. You will never get a good front drive shaft angle because the front Xfer case shaft is tilted up and the pinion angle is horizontal or pointed down to get a caster angle + 4 or 5*. I have since installed The Yukon free wheel hub disconnects to eliminate the need to ever have to worry about drive shaft balance and to give me the option of 2 wd low range. Just like my CJ in high range my TJ will roll very easily on level ground and rapidly pick up speed on down hills with no throttle input and require downshift or using brakes to maintain speed.
Just my experience with TJ drive line vibrations.

As far as front output of xfer tilting up, belly tuck should have effect on the harmonic vibes, but it does not. Same thing for changing pinion angles of front and rear.
Its a rabbit hole theory that belongs in countless multi page threads on this mystery.

 

[freedom_in_4low]

I had harmonic vibrations, then I realized I had a Beach Boys CD in and it was playing good vibrations.

Sorry couldn't resist!!

and I've now had that song in my head for going on 20 hours.

 

[Vtx531]

How are your tub body mounts. Not rusted out, are they?

 

[John Middleton]

You never said what dif. ratio you are running. 04 Rubi 4 1/2" lift w 5.13 had the same problem. dumped thousands of $ for over a year and a half with no joy. Replaced drive shafts with Woods, no change .Raised / lowered T case Etc. Rebuilt front diff because of failed pinion brg from vibration.. Had drive shafts re-balanced, no Change. Rebuilt Xfer case, front out put bearing was worn from vibrating. Stumbled upon a you tube video on European drive shaft balancing machines that are capable of 10,000 rpm used on manufacturing machinery. Watched you tubes on drive shaft builders and all of the big time builders only balance to 3,000 rpm MAX. I called several BIG name builders and none had the capability to balance over 3,000 rpm. With my 5.13s with 35" tires I am turning over 3500 shaft rpm at 70+ mph although vibration starts at 55 and progressively got worse as speed increased. Denny's Driveshaft in Kenmore, New York is the only shop I found in the US that can and will balance a shaft to 10,000 rpm. I ordered a new shaft and requested it balanced to 6,500 rpm. I installed and no vibration up to 90+ mph. The imbalance is in the double carden joint center section angle due to cardin joint angle. You will never get a good front drive shaft angle because the front Xfer case shaft is tilted up and the pinion angle is horizontal or pointed down to get a caster angle + 4 or 5*. I have since installed The Yukon free wheel hub disconnects to eliminate the need to ever have to worry about drive shaft balance and to give me the option of 2 wd low range. Just like my CJ in high range my TJ will roll very easily on level ground and rapidly pick up speed on down hills with no throttle input and require downshift or using brakes to maintain speed.
Just my experience with TJ drive line vibrations.

Thanks for your post. I’m running stock axle ratio w/ 265/16 Michelin ATX tires on stock rims. So yesterday I pulled tranny mount (Mopar installed 2021) based on mechanic’s rec. it looked brand new. Reassembled the Jeep & tightened tranny mounts w/Jeep sitting on all fours & went off-roading today (180 total miles) . Vibration unchanged Except, I pulled out onto hiway & tan up to 70 mph while still in 4WD (no lectures please). The vibration was negligible but present: much improved-go figure!
putting lockouts on front axle is a great idea & may be my best option!