Vibrations

Back to the experts! Finally got to take a few longer drives yesterday. Got side pipes put on and can hear more now that it's not straight headers! I noticed while driving I have a vibration on accerleration and deceleration. Ones as bad as the other. There's a sweet spot if you just when you go from throttle to coast that's smooth as silk. I didn't get a chance to throw it in netural to see if that made a difference. 2.5 inch lift with shims installed that came with the kit. Rear end feels tight, ujoints are newish and greased and tight. Just a tad of play at the yoke on back of the transfercase. Just enough to know it's there. Reckon that's where it's at? Angle at pinion isn't sever at all and almost pointing at transmission but just a slight angle still .

 

How's it Running ? ( Could be engine vibration). Also I've left my front hubs locked in while running in 2 Wheel Hi . That could do it too, but I'm thinking timing or Points or carburetor? You said that if you catch the ' Sweet Spot ' from load to no load, could very well be the timing or dwell is off ?
Then again, could be something like a Throw out bearing , if you dump in the clutch to coast ?

 

Driveshaft u-joint?

 

Both u-joints in the driveshaft have to be in phase and at equal, or near-equal angles. Watch this video and compare to what you have.

 

Could be U-joints or alignment or tire balance. Tire balance and alignment cause resonance and can be driven through. U-joints just vibrate more with speed.

 

Engine runs smooth as silk. I'm leaning towards driveline vibration. I had a wrangler years ago and got into vibrations when I lifted it 8 inches. seems like I cut perches and re angled the rear end but that's been a long time ago. First though u joints but it's pretty consistent at all speeds. I would have like to have known how it drove before the lift. I bought it not running before I rebuilt it. Just trying to start with the easiest solutions and go from there.

 

That video explained alot. Maybe I should remove the shims and try it.

 

Usually when the vibration occurs when power is applied, and conversly under decelleration load, its a driveshaft angle or bad u-joint. This is assuming the driveshaft splines are lined up so the u-joints are in the same plane with each other.
Unless you have a double cardin joint, you don't want the pinion to point to the transmission.
-Donny

 

I would think driveline. Could be a slight bend in the drive shaft too. Is there a place near you that can check the drive shafts out for balance and being straight?

 

I'm going to try to remove the shims tommrow and see if it improves. That should put the angle similar to the angle at the tranny.

 

Remove the rear shaft and drive it on the front.
See if anything changes.

 

Or lower tranny cross member. But you are on the right track to keep angles close to the same.

 

My first place to look is drive lines bale and health of u joints

 

Sorry balance

 

I took the shims out that came with the lift springs. Pinion angle is close to angle at tranny now. Took it for a spin and vibrations are gone! Thanks for the help guys! Funny thing is it drives amazingly better now. Drives how a jeep should drive. The dart that The steering had is gone. Can anyone explain this?

 

Driveline misalignment can impart heavy burtations into other parts of the vehicle. It's science.

That's pretty cool to have fixed both issues. Was anything loose? Maybe the shackle bushings had been tightened with one wheel in the air, causing the system to be sort of wound up on one side? The work you did fixed SOMETHING else. Cant see how the vibes would cause squirrelly steering, other than burtations of course.

 

Nothing was loose. Very strange that it fixed the handling issue. Hit 50 mph on my curvy road that 30 was sketchy last trip out.

 

We’re the center bolts in the holes on the perch? When my perches collapsed it got all weird when on the throttle or when letting off It would pull left under acceleration and right on deceleration Loose bolts will make it all stupid too.

 

No they were lined up and ubolts we're tight. Strange but a good thing.