Powertrain/ ??? vibration

Glava

Veteran Member
Lifetime Gold Member
Mar 23, 1999
458
Central NY
We were able to install a set of 79 Trans Am rims with tires and no vibration.
They said that the taper on a few of them looked messed up along with the rim holes.
They didn't determine which rim/ tires vibrated, so I am going to look at that and start with a rim on bad ones -hopefully it will only be one or two rims, but I figured that I'll try the rims first and hopefully find that the Goodyears with only 1k miles are OK.
 

mallard

Veteran Member
Oct 3, 2013
1,880
SK, Canada
Excellent that you now know generally what’s causing your vibration. One question, had you ever tried rearranging the tires/wheels that were on the car to see if the vibration changed? In any event you should now be on the road of ridding yourself of this issue forever. Congrats!
 

Glava

Veteran Member
Lifetime Gold Member
Mar 23, 1999
458
Central NY
Excellent that you now know generally what’s causing your vibration. One question, had you ever tried rearranging the tires/wheels that were on the car to see if the vibration changed? In any event you should now be on the road of ridding yourself of this issue forever. Congrats!
Been up at camp, so just circling back to up date. Yes, we rotated and changed positions and still had the vibration. The mechanic stated that vehicles have hub centric or lug centric locating designs and that there rims are lug centric-so any distorted holes or lugs can potentially cause vibration. Since we can see this issue on at least two of the rims and lug nuts, I’m looking at that as the next thing to attack. So I ordered (4) reproduction rims from OER. They will be here next week. I’m then going to paint them to match the body color and drop them off to have them installed & balanced with my tires.
 

Glava

Veteran Member
Lifetime Gold Member
Mar 23, 1999
458
Central NY
I have been trying to get find the source of a drive train, seat of the pants, vibration that my 79 z/28 with a four-speed transmission has for as long as I can remember.
It probably is going to end up being one or more of the retro Goodyears, which have about 600 miles on them, not being able to be balanced.
The best test is next week when a garage friend of mine is going to swap the rims/ tires off of his sons 79 Trams Am onto the Z/28 and see if the vibration goes away.
Quick recap; it is a 31k original mile Z/28 that I've had since September 79 -it was a June 79 build.
I checked the pinion/ shaft angles and they appear to be OK. I did change out a bad rear transmission mount.
The vibration is at just over 60MPH, and most often I just run around town, so it hasn't been a major issue, but I want to get it fixed.
The vibration was there with the original Uniroyals and seemed to be the same or maybe a little better when I got the new Goodyears -so last year I actually had the Goodyears road force balanced to see if it could be fixed and they actually seemed a little worse..
One thing that I had thought was that one of the original rims may have been the problem - I did change one that they said was out of round years ago and it made no real difference.
I also wondered if the drive shafts for the auto and standard were the same length, and did find that the M21 Borg Warner T-10 had its own driveshaft part number -PN 7819345. So another longshot question is if they put in the other drive shaft PN 7819344, if it even fit, could that cause a vibration in the driveline?
I'm not sure where i can find the lengths etc., to compare.
My drive shaft has two 1" wide yellow stripes about 5" apart.
Anyone know if that could be an issue?
Now it is possible that everything will hopefully be sorted out when we do the rim/ tire swap testing.
If no vibration, we can swap in mine one at a time and find the bad one for sure -fingers crossed.
Ok, I ordered (4) OER rims, painted them white as original and had them mounted and balanced -no vibration at 65!!
So the original rims are apparently a softer steel? and over the years, they got elongated plus I think when I had the tires changed over a few years ago, I had found two a couple of weeks later were a little loose.
I have taken the Z up to camp for the summer, so it will get more driving time -only been averaging about 200miles/ year for the last 25+ years.
The 140 mile drive to camp is probably the longest road trim ever. The 3.73 gears,, close ratio 4 speed are not the best road gears -just over 3k rpm at 65mph. And boy does it suck not having cruse control.
So this year I'm going to have regular local fun rides up at camp and we will definitely break 32k miles this year!
 

mallard

Veteran Member
Oct 3, 2013
1,880
SK, Canada
Congrats on the fix. You must have had a defective wheel or two from square one that likely worsened with age. Great results! 👍
 

Chevyforever

Veteran Member
Jan 4, 2011
1,439
Ontario, Canada
Yes, glad you've finally got that pesky issue sorted out. I stated on another thread on here a few years ago that I thought that style of wheel was centered by lugs and one of the "regulars" here was quick to disagree, I feel redeemed.
 
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kenny77

Veteran Member
Lifetime Gold Member
Jul 31, 2001
3,275
Ft. Lauderdale, FL
Been up at camp, so just circling back to up date. Yes, we rotated and changed positions and still had the vibration. The mechanic stated that vehicles have hub centric or lug centric locating designs and that there rims are lug centric-so any distorted holes or lugs can potentially cause vibration. Since we can see this issue on at least two of the rims and lug nuts, I’m looking at that as the next thing to attack. So I ordered (4) reproduction rims from OER. They will be here next week. I’m then going to paint them to match the body color and drop them off to have them installed & balanced with my tires.
Well he's wrong. Any stock wheel on a Camaro is HUB Centric. If when you put the wheel on the car, and you have to center it to even go over the brake drum or rotor hub center.. and it fits tightly like our wheels do....guess what.. .that's called Hub Centric. .
Your wheel or wheels are bent or twisted somewhere else, and he couldn't find it or show it to you so that's what he told you
 
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kenny77

Veteran Member
Lifetime Gold Member
Jul 31, 2001
3,275
Ft. Lauderdale, FL
Ok, I ordered (4) OER rims, painted them white as original and had them mounted and balanced -no vibration at 65!!
So the original rims are apparently a softer steel? and over the years, they got elongated plus I think when I had the tires changed over a few years ago, I had found two a couple of weeks later were a little loose.
I have taken the Z up to camp for the summer, so it will get more driving time -only been averaging about 200miles/ year for the last 25+ years.
The 140 mile drive to camp is probably the longest road trim ever. The 3.73 gears,, close ratio 4 speed are not the best road gears -just over 3k rpm at 65mph. And boy does it suck not having cruse control.
So this year I'm going to have regular local fun rides up at camp and we will definitely break 32k miles this year!
Excellent. How did you paint them?. I have one on my car that's a bit bent I'm afraid
 




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