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rear end vibration (1/8)
 3/5/18 12:59am
Aquaman0169
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Hermitage, TN - USA

Vette(s):
1971 Convertible, Mille Miglia Red with Red interior. 350/ 270HP TH 400 3.55 gears, Air Conditioning, PS, PB,. I bought this Corvette in April, 1998 the same week I found out I was going to be a Father for the first time (two daughters).


Joined: 3/4/2018
Posts: 5

I have a rear end vibration at 60 to 65 mph that is harsh enough to cause the driver side rear marker light lens to come off somewhere on the highway.
I recently rebuilt all 4 calipers, installed 4 new rotors, and new pads all the way around.
In the process of "truing" the rear calipers for minimum runout, I removed both half shafts from both the differential and flanges.
I have a feeling that I have put the halfshaft(s) in a different position than I removed them, as I had no vibration like this before I began my brake project.
Does anyone have any ideas on how to get the halfshafts back to a "balanced" position to eliminate the harmful vibration?  I have calculated that there are 16 different combinations to install both of the half shafts in.  As you know, the task of trying each of the 16 different combinations is very time consuming and frustrating...hoping each try takes the vibration away during the up to speed road test.
Thank you for your time and consideration.
Sincerely,
Andy
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Re: rear end vibration (2/8)
 3/5/18 9:45am
knotacare
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Newark, DE - USA

Vette(s):
1968 Conv, 454HO,500HP-600TQ, TKO-600,3:70 HD rear,hotrod air, custom paint & suspension,1973 Ruby Red,T-top, 383 Stroker, TK)-500,frame off restro, 1977 Yellow (1 of 51 ) L-48 4 spd, 99% original.


Joined: 7/26/2004
Posts: 461

I would take the driveshaft & halfshafts to a driveshaft shop & have them all checked for balance.  It shouldn't matter how you attach them as long as they are balanced.  If the vibration continues you've got another problem.
Alan


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Re: rear end vibration (3/8)
 3/5/18 1:25pm
Adams' AppleLifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas


Joined: 11/8/2003
Posts: 19627

It's common practice to mark the half-shaft flanges on the outboard side, and the yokes on the inboard side to get them back where they were, but it is NOT totally necessary. If you had no vibration before, I would assume that either the flange(outer) ends are not properly seated on the wheel hub flange, or the u-joint(s)(inner) are not properly seated into the differential yokes. The stock half-shafts are not normally balanced, nor do they normally need to be.
If there is any play in the rear hub bearings, shimming the rotors to get the run-out correct will aggravate any slight vibrations that might have been there before. Thumbs Up

I would suggest you NOT continue to drive it until you determine the issue. If one(or both) of the half-shafts comes loose from either end while driving, it will absolutely ruin your day.....and most of the back end of the car....Censored

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Joel Adams
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Re: rear end vibration (4/8)
 3/5/18 11:45pm
Aquaman0169
Former Member

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Hermitage, TN - USA

Vette(s):
1971 Convertible, Mille Miglia Red with Red interior. 350/ 270HP TH 400 3.55 gears, Air Conditioning, PS, PB,. I bought this Corvette in April, 1998 the same week I found out I was going to be a Father for the first time (two daughters).


Joined: 3/4/2018
Posts: 5

I know I should have scribed or punch marked the flanges and corresponding half shafts...the Sharpie I used came off during the long process and I had to guess at placement. Half shafts are definitely on correct side of rear end. Thinking about this more, I recall one of the ujoints on the outboard side (flange end) was tight, unlike the other 3 joints. Maybe this ujoint (I installed about 10 years ago and have driven about 10, 000 miles on) is the cause, but it was on the car beforevtge brake job.
Re: rear end vibration (5/8)
 3/6/18 8:56pm
F4Gary
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Grapevine, TX - USA

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1972 LT-1 convertible with factory air.


Joined: 8/26/2006
Posts: 963

Could be a wheel.  I know 1 or 2 of my old wheels flunk the roadforce test when Discount Tire tried to balance them.

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Re: rear end vibration (6/8)
 3/6/18 10:37pm
Adams' AppleLifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas


Joined: 11/8/2003
Posts: 19627

Aquaman0169 said:Thinking about this more, I recall one of the ujoints on the outboard side (flange end) was tight, unlike the other 3 joints. Maybe this ujoint (I installed about 10 years ago and have driven about 10, 000 miles on) is the cause, but it was on the car beforevtge brake job.

Yes...but you disturbed it while it was off the car. In doing so, it may have shifted the needle bearings in the cap(s) enough to throw it out of whack. Moving the flange joint by hand off the car will move it far more than it will with it bolted to the hub while driving.....unless you happen to do some off-roading, that is. Big smile

Can you tell what side of the car is vibrating? 



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Joel Adams
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             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
Re: rear end vibration (7/8)
 3/8/18 4:17pm
Aquaman0169
Former Member

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Hermitage, TN - USA

Vette(s):
1971 Convertible, Mille Miglia Red with Red interior. 350/ 270HP TH 400 3.55 gears, Air Conditioning, PS, PB,. I bought this Corvette in April, 1998 the same week I found out I was going to be a Father for the first time (two daughters).


Joined: 3/4/2018
Posts: 5

Good thought, but not likely in this case as this is a new vibration that did not exist before I took on the brake replacement project.
The tires and wheels were stored next to the car in my garage and were placed back in the same location on the car as before I started the brake project.
Thank you for your thought and time.
Re: rear end vibration (8/8)
 3/8/18 4:24pm
Aquaman0169
Former Member

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Hermitage, TN - USA

Vette(s):
1971 Convertible, Mille Miglia Red with Red interior. 350/ 270HP TH 400 3.55 gears, Air Conditioning, PS, PB,. I bought this Corvette in April, 1998 the same week I found out I was going to be a Father for the first time (two daughters).


Joined: 3/4/2018
Posts: 5

I understand your train of thought.
I do not do any off road driving, only local city streets and some freeway runs.

I believe I will remove and turn the half shaft on each side 180 degree at the inboard (rear end gear) side, one at a time, with a road test to speed in between, to see if moving them have any effects, negative or positive on the vibration.

The rear marker light lens on the driver's side is the one that came off due to vibration.  I believe from this that the driver's side is the one that is causing the vibration.  However, the half shaft ujoint that I recall being tight was on the passenger side.

If changing the position of the half shafts on the inboard side does not improve or eliminate the vibration, I will inspect the tight ujoint on the passenger side and regrease if not damaged to see if it loosens up and feels like each of the other 3 ujoints (that were all replaced at the same time).

Thank you for your help,
Andy