Vibration at speed - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Transmission - Rearend
User Name
Password
lost password?   |   register now

Closed Thread
 
LinkBack Thread Tools
  #1 (permalink)  
Old 09-17-2004, 01:27 PM
Member
 
Join Date: Oct 2003
Posts: 82
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Vibration at speed

Iím posting here but it could very well go somewhere else. Just guessing.

1967 Belvedere with 727 3.55:1 gears

Iím experiencing a harmonic vibration that comes in one second intervals. The vibration is in the seat of the pants (and up the back!), goes through the car for one second, one second rest, then repeats. Does not affect steeringóno steering vibration.

Things I have checked:

New tiresóspin balanced. Vibration was there with old tires and with new tiresóno difference.
Front end alignment on target.
Drive shaft balanced. U-joints good. Drive shaft does not demonstrate out-of-balance rotation when checked.
Motor mounts good.
Front suspension good. Tie rods, ball joints, pitman arm ok, greased, no looseness.

Vibration is SPEED specific, not RPM specific. Above 45, vibration begins and continues through 75-80 or even higher mph. No smoothing out so I donít believe it is caster shake. Below 45, regardless of RPMís, no vibration.

Things to check next?

    Advertisement
Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 09-17-2004, 02:07 PM
suck, squeeze, bang, blow
 

Last journal entry: finally reeled it in
Last photo:
Join Date: Jul 2004
Location: Ontario, Canada
Age: 42
Posts: 169
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Just a thought, I've had vibrations caused by the brakes. The parking brake was not releasing all the way and caused a vibration over about 60 km/hr. the only reason I caught it was because I pulled on the brake cable and it released. Another time it was a slightly seized caliper and a rotor that was warping more and more because of the heat, the hot rim was a dead give away. That's a vibe that rips through the back.

I've heard that radial tires on older cars can sometimes cause harmonic vibrations. The running frequency of radials is different from bias ply tires and can cause the suspension components to oscillate at their natural frequencies. I've never experienced it for myself, so I don't know exactly what it sounds or feels like.

A pilot bearing for a manual transmission will also cause vibrations like you're describing, and disengaging the transmission doesn't always stop the vibe.

How are the wheel bearings? I've had a noisy vibe when I let the wheel bearings go, but it's not really the kind that will jostle the spine, just annoy the ear drums.

I've had a similar vibration caused by a malleable iron harmonic balancer starting to come apart. It didn't vibrate when the engine was disengaged from the transmission, but it did vibrate over a certain speed. When the engine was disengaged over that speed, the vibration would stop. You probably got the car to speed and flipped it into neutral to check this, I assume that's what you meant by not RPM specific.

With out going into the transmission, That's about all I can come up with, good luck.
Quick reply to this message
  #3 (permalink)  
Old 09-17-2004, 02:37 PM
Member
 
Join Date: Oct 2003
Posts: 82
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Yeah, it's an automatic, so the pilot bearing thing is out.

A friend suggested wheel bearings, but I agree with you. Usually they just make a terrible racket, but don't cause a nice harmonic vibration--and I mean IT'S A VIBRATION. You feel it through the entire car.

The radial tire explanation I guess is possible--others have suggested it. But I've driven almost every kind of "old" car out there and invariably adding radial tires usually just improves handling without any other symptoms. I guess this could be the exception, but...

The harmonic balancer looks brand new. I haven't checked for slippage--will do that.

Speaking of the transmission, could a poorly meshed rear gear set do this? I've heard that you need the mesh pattern down right, otherwise it could be a problem.

I raise that issue because it is a fairly new tranny--not sure when it was rebuilt--but supposed to have been recently.

Another idea a friend has had is a bad or out of round axle. Possible?
Quick reply to this message
  #4 (permalink)  
Old 09-17-2004, 03:24 PM
suck, squeeze, bang, blow
 

Last journal entry: finally reeled it in
Last photo:
Join Date: Jul 2004
Location: Ontario, Canada
Age: 42
Posts: 169
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Out of round Axle is possible, if you mean out of round at the bearing surface. I haven't heard of axles going out of round from wear or stress, and I don't know what a bad axle is so I can't comment. The ones I've worked on usually go out of round at the bearing surface, (usually because of the bearing) so If you're going to check the bearings, you'll see it. If that's the case, see if you can get an axle repair bearing. It's the same bearing, but the case is made so the bearings run a little further in (or out) on the axle surface. I don't think you're going to get off that easy though because you probably would have heard the vibe from the bearing wearing out in the first place, unless the bearing just fell apart.

Another thought is the diff. carrier bearing. My experience is with cars a little newer than yours so I don't really know how yours is set up, but I would pull off the diff. cover and check things out. Probably a good time to do an oil change and slide in that new synthetic oil. (I'm so sold on that stuff, 463 000kms on my diff. with no problems) I'd start there before checking out the trans, although checking the rear output shaft for play is pretty easy too.

I had a vibe in a chevy van that I couldn't find for the life of me, the kind of vibe that made looking in the mirrors impossible. It was the planetary gear in the trans missing a half a dozen teeth. Of course that meant a rebuild, so I'd try looking for the simple stuff first.
good luck
Quick reply to this message
  #5 (permalink)  
Old 09-17-2004, 04:02 PM
stu stu is offline
Member
 
Last photo:
Join Date: Aug 2004
Location: Saskatchewan
Age: 73
Posts: 428
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
A few things to look at.

Alignment of the drive shaft U Joints.
Raise the vehicle on a lift and look down the drive shaft from the differential.
The ujoints should be in line.
If you see the front one off a bit the transmission mount has slipped.
The mount has a bolt going through a rubber mount.
After several years the rubber will deteriorate and the drive train will move sideways one way or the other.
Also check to see if the transmission isn't resting on the cross member. Again from a bad mount.
The engine mounts can cause this as well.
If one is sagged it will upset the apple cart.
Don't want to lose all your precious apples.
Quick reply to this message
  #6 (permalink)  
Old 09-17-2004, 05:26 PM
Registered User
 
Join Date: Sep 2004
Location: minnesota
Age: 41
Posts: 8
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Maybe a bad torque converter? You can DEFINITELY feel a bad vibration when those are out of balance or internally damaged. Although I'd think that would be more rpm specific.
Quick reply to this message
  #7 (permalink)  
Old 09-17-2004, 08:52 PM
Member
 
Last photo:
Join Date: May 2003
Location: Shreveport LA
Age: 64
Posts: 5,103
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Does the pitch of the vibration change between 45 & 75mph?
Quick reply to this message
  #8 (permalink)  
Old 09-20-2004, 09:30 AM
Member
 
Join Date: Oct 2003
Posts: 82
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
For Jimfulco:

Yes, the pitch of the vibration changes between 45 and 75. The worst is dead on 60 mph. At that speed, the vibration is a nice, steady harmonic hum through the body in one second intervals with one second between vibrations.

At 75, the harmonic vibration seems to be quicker (faster) in its resonation, and sometimes you "think" it has disappeared because it is vibrating so rapidly through the car. But, you can still feel it--more like a constant hum or vibration as the car moves down the highway. Then you drop it down to 60 mph and the one second intervals begin again.

For flyfisher and Stu:

Both of your suggestions seem like possibilities. I had the car up on a lift previously and the tranny mounts looked okay, but then again, I wasn't looking specifically for that as a trouble spot. So, next chance I get I'll check that out along with the axle/wheel bearings and the diff. carrier bearing.
Quick reply to this message
  #9 (permalink)  
Old 09-20-2004, 12:06 PM
Siggy_Freud's Avatar
Hotrodders.com Moderator
 
Last photo:
Join Date: Dec 2003
Location: Portland, Oregon
Age: 29
Posts: 2,371
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
Id be interested to hear the solution as I am having the EXACT same problem. I too have replaced the driveshaft, motor mounts, tranny mount, ujoints to no avail.

In the past I had a brake rubbing the drums and am starting to wonder if this could be the case again. I also plan on inspecting the rear end here shortly and will be sure to let you know if I find anything.

Hope this gets figured out for both our sakes lol.
__________________
Bringing history and technology together.
Quick reply to this message
  #10 (permalink)  
Old 09-20-2004, 12:55 PM
Vista Cruiser's Avatar
New Member
 
Join Date: Jan 2004
Location: Wichita, KS
Posts: 25
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
I have been fighting the same type of problem for the last 2 weeks or so on my 66 Caprice. I replaced the engine and tranny mounts, had the drive shaft balanced, had the tires rebalanced, all to no avail. Previously, while I had the brakes apart, I had the brake drums powder coated. I'm thinking the sandblasting and powder coating changed the balance on the drums. This weekend, I replaced the two front drums with a set from the salvage yard. The low-speed, 45-60 mph vibration went away, but I still feel it at around 70 mph. I'm going to replace the rear drums tomorrow to see if that eliminates the problem completely. I'll let you know what I find out.

JimR
Quick reply to this message
  #11 (permalink)  
Old 09-20-2004, 01:01 PM
Member
 
Join Date: Oct 2003
Posts: 82
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
I would be very interested in Vista Cruiser's results. My brakes appear to work fine, but not in reverse. That is, I really have to stomp on the vacuum assisted power brakes to make the car stop while in reverse. Braking while moving forward is no problem.

I would not have imagined that it could be out-of-round drums or brakes that could cause such a vibration.

Let us know what you find as soon as possible. I'd rather tear into the brakes than the tranny or differential.
Quick reply to this message
  #12 (permalink)  
Old 09-20-2004, 01:41 PM
66Caprice's Avatar
Move It On Over!
 
Last photo:
Join Date: Jun 2004
Location: Tucson, AZ
Age: 54
Posts: 227
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
I had a similar problem like that caused by a rear u-joint not perfectly centered on the mount. It was only about 1/8" offcenter, but it was enough to cause vibrations around 60mph and faster.

It was not the right u-joint. My drive shaft is custom and the ujoint lengths are different on the x-y axis. It took a while to find the right one that fit, but since then, there's been no vibration problems.
Quick reply to this message
  #13 (permalink)  
Old 09-20-2004, 01:48 PM
poncho62's Avatar
Out of the Loop Moderator
 
Last wiki edit: Streetbeasts links
Last journal entry: at car show
Last photo:
Join Date: Oct 2003
Location: Hanover, Ontario, Canada
Age: 62
Posts: 16,931
Wiki Edits: 5

Thanks: 22
Thanked 288 Times in 226 Posts
Wheel bearings............................
__________________
Ontario Rodders

Budget RVs
Quick reply to this message
  #14 (permalink)  
Old 09-21-2004, 10:11 AM
dawg's Avatar
NAVY VETERAN
 
Last photo:
Join Date: Aug 2004
Location: Colebrook Connecticut
Age: 55
Posts: 912
Wiki Edits: 0

Thanks: 0
Thanked 7 Times in 5 Posts
check drums, rotors for runout
flywheel out off balance.
loose rear spring mounts
etc.
basically anything that rotates is suspect.
Quick reply to this message
  #15 (permalink)  
Old 09-21-2004, 10:42 AM
stu stu is offline
Member
 
Last photo:
Join Date: Aug 2004
Location: Saskatchewan
Age: 73
Posts: 428
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Also.
Have a look at the pinion angle.
It could be too high or too low.
Quick reply to this message
Closed Thread

Recent Transmission - Rearend posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -6. The time now is 10:27 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.