Jump to content

Minor vibe while passing through 45MPH


Recommended Posts

Just throwing this out for some opinions. Finished the D44 regear and install, got the leaks fixed, and am out driving semi aggressively until the diff gears get steeled in. This vibe is not a big problem, but I like things right. I get a very minor harmonic vibe through the butt dyno and in the steering wheel while passing through 45-50 MPH. Below and above is perfect, all the way to the speedo pegs @ 85MPH. I get it both accelerating and coasting thru this 5MPH band only. The drive shaft was shortened 1" for the D44 by a good shop, and rebalanced. Tires are all in the same positions as with the previous D35. I also replaced the upper control arms and bushings during the D44 down time. I can easily live with this vibe problem, but it bugs me. :hmm:

 

To test, went out on the interstate today with the wifey following in her Malibu SS. The goal was to see if I could find a second harmonic vibe at higher speed to help troubleshooting. Rammed the stroker past 4K RPM, speedo was pegged, smooth as silk all the way. My speedo is calibrated and correct. Wife said I was past 95MPH and rising on her clock when she backed off. There was no second harmonic. Smooth all the way.

 

All in all, feel good with the new 4.10 44 axle, but WTF could be causing this stupid 45-50 MPH vibe?

Link to comment
Share on other sites

U-joints are less than six months old. Hopefully it just threw a wheel weight. Bout time to have them balanced anyhow.

 

The axle change still did slightly change their angle of operation, even if the pinion angle was correct. If balancing the wheels doesn't do it, I'd change the U-joints anyway.

Link to comment
Share on other sites

The axle change still did slightly change their angle of operation, even if the pinion angle was correct. If balancing the wheels doesn't do it, I'd change the U-joints anyway.

 

This is true since the drive shaft is an inch shorter. The pinion angle still checks out right w. the olde angle finder. Noticed also the steering wheel moved about an inch ccw off center after changing the UCAs. Might as well have them check the alignment too.

Link to comment
Share on other sites

My GF got a '07 Dodge 1500 with them big a*sed 20 inch extra wide rims on it. They sure are pretty but next to useless on this road. Several times they have gone flat and when I busted the tire off the rim I found hand fulls of mud in side the tire. Where going thru a mud hole the mud would push the side wall off the rim, get inside and hold the tire off the rim enough for a slow leak. Then when hitting the pavement it would vibrate and shimmy sometimes mild, sometimes violently until the crud finally got slung off the rims. Now she parks it when the roads are bad and drives my lowly XJ.

Link to comment
Share on other sites

If the alignment and balancing doesn't get rid of the vibe I would replace the ujoints as previously mentioned. They are now at slightly different angles and out of their wear pattern.

 

How is the slip yoke riding? Is it possible with the driveshaft shortening that it is pulled out of your transmission some, thus not providing as much spline to spin on?

Link to comment
Share on other sites

Is there a hoist of some kind around there you could use to raise the Jeep and put a strobe on the drive train? Just a thought.

Used to be. Had a good friend, an old Navy buddy, who ran a muffler shop here. It had five bays, four with lifts and I could go there just about any time and use one if it was free for beer. :cheers: Even had a key so I could go in there on the weekends when he was closed. He retired last year and sold out. The new guy is a real redneck tool and I haven't been back since. Sure miss that place. :( I'm hoping an alignment and balancing will take care of it.

 

How is the slip yoke riding? Is it possible with the driveshaft shortening that it is pulled out of your transmission some, thus not providing as much spline to spin on?

Spline engagement is the same as with the D35, so I don't think so. It's a real quick vibe, ON at 45; OFF at 50. No where else. It's actually much smoother than it was before across the band. I'll keep in mind the u-joints though. Dayem, I hate replacing them.....

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...