Vibration between 64 and 70 mph
Thread Starter
Instructor
Joined: Jul 2012
Posts: 235
Likes: 9
From: Winter Garden Florida
Vibration between 64 and 70 mph
this is on an '86 coupe auto. 80K miles
I had the universal joints in the drive shaft and the half shafts checked by the local expert corvette mechanic and all he could find wrong was a bad bushing and seal in the rear tranny tail shaft and he replaced both.
while there I had him drain and replace the rear differential oil and GM additive. he said there was no metal in the old oil. but he also replaced the rear pinion seal because it was starting to drip.
the tires are new and I took them back to the shop and had them rebalanced anyway.
below 64 and over 70 it is smooth but, in between those speeds it has a vibration I can feel in the seat of my pants. the steering wheel is very steady and the car is without any noise. no chirping or squeeling.
where do I check next? I want to avoid telling the mechanic to just fix it.
wheel bearings? bent half shaft?
all help is appreciated
John
I had the universal joints in the drive shaft and the half shafts checked by the local expert corvette mechanic and all he could find wrong was a bad bushing and seal in the rear tranny tail shaft and he replaced both.
while there I had him drain and replace the rear differential oil and GM additive. he said there was no metal in the old oil. but he also replaced the rear pinion seal because it was starting to drip.
the tires are new and I took them back to the shop and had them rebalanced anyway.
below 64 and over 70 it is smooth but, in between those speeds it has a vibration I can feel in the seat of my pants. the steering wheel is very steady and the car is without any noise. no chirping or squeeling.
where do I check next? I want to avoid telling the mechanic to just fix it.
wheel bearings? bent half shaft?
all help is appreciated
John
Race Director
Joined: Apr 2009
Posts: 19,294
Likes: 2,754
From: Charlotte NC
First off...I hope you and your mechanic are aware that it takes special teflon coated U-joints for the driveshaft AND half shafts due to they are made out of aluminum and it REQUIRES a COATED U-joint. THIS IS FACT...NOT my opinion. Using a U-joint that is NOT coated will cause the aluminum to powder away (due to galvanic action) and the caps of the U-joint will now have play in them. The caps of the U-joints should look dull and have NO SHINE to them like "normal U-joints". And you can tell if the caps are correct by easily looking at the ends of the caps (where the clip would be installed to keep it from moving...or the straps that bolt it to the yoke or rear differential flange.
No "blobs" of undercoating or dents should be on/in your half shafts.
Not "knocking" your mechanic....but I hope he marked the way the driveshaft was positioned in relation to the yoke.....and if my memory serves me correctly...the position on how the driveshaft was located on the rear differential flange...as per the GM service manual.
Was the vibration there before any U-joint service???
DUB
No "blobs" of undercoating or dents should be on/in your half shafts.
Not "knocking" your mechanic....but I hope he marked the way the driveshaft was positioned in relation to the yoke.....and if my memory serves me correctly...the position on how the driveshaft was located on the rear differential flange...as per the GM service manual.
Was the vibration there before any U-joint service???
DUB
Drifting
Joined: Jul 2004
Posts: 1,356
Likes: 291
From: MA
Dub, I got the impression his mechanic checked the u-joints but did not change them!
I had a very similar issue with my 96 vibration around 75-85 then went away above these speeds. I ended up changing the halfshaft u-joints on both sides. And while I was inspecting everything back there I noticed all my suspension bushings were cracked and binding. My suspension literally would not droop when I put the rear up on jack stands.
When I pulled the rear knuckles off I left the dog bones connected. I saw shiny sections with a very slight groove in the dog bone mounting brackets!
It took quite a bit of force to even pivot the dog bones up and down.
The camber rods were also in the same shape.
I changed them out to polyurethane (Prothane with lots of marine grease).
After replacing everything the vibration is gone! Now the car is put away for the winter but I am going to check the front end bushings next year.
I had a very similar issue with my 96 vibration around 75-85 then went away above these speeds. I ended up changing the halfshaft u-joints on both sides. And while I was inspecting everything back there I noticed all my suspension bushings were cracked and binding. My suspension literally would not droop when I put the rear up on jack stands.
When I pulled the rear knuckles off I left the dog bones connected. I saw shiny sections with a very slight groove in the dog bone mounting brackets!
It took quite a bit of force to even pivot the dog bones up and down.
The camber rods were also in the same shape.
I changed them out to polyurethane (Prothane with lots of marine grease).
After replacing everything the vibration is gone! Now the car is put away for the winter but I am going to check the front end bushings next year.
Thread Starter
Instructor
Joined: Jul 2012
Posts: 235
Likes: 9
From: Winter Garden Florida
it is correct that the U-joints were not replaced but just checked. my mechanic did have to remove the driveshaft to replace the bushing and seal in the rear of the transmission and to replace the pinion shaft seal in the rear end.
I was un aware that a frozen bushing in the dog bone would cause a vibration , is that correct?
I will look into these items and keep everyone posted.
keep the suggestions comming
thanks,
John
I was un aware that a frozen bushing in the dog bone would cause a vibration , is that correct?
I will look into these items and keep everyone posted.
keep the suggestions comming
thanks,
John
Safety Car
Joined: Apr 2011
Posts: 3,660
Likes: 22
If the drive shaft was pulled, its possible the "tune" of the shaft was changed as Dub suggested.
Driveshaft "tune" is the correct positioning of the shaft at 90 degree angles to the joints where the balance weight was placed on the shaft,. so it can be 90 or 180 out based on where the original position was.
There is a weight on the shaft somewhere. If it did not go back in the same way as it came out, its out of balance..or tune.
Driveshaft "tune" is the correct positioning of the shaft at 90 degree angles to the joints where the balance weight was placed on the shaft,. so it can be 90 or 180 out based on where the original position was.
There is a weight on the shaft somewhere. If it did not go back in the same way as it came out, its out of balance..or tune.
Drifting
Joined: Jul 2004
Posts: 1,356
Likes: 291
From: MA
jgalfo, If you run your car up to the speeds that cause the vibration and then put the car in neutral. Does the vibration stay or go away?
If it goes away it could be engine related. If it stays which it probably will. It could be transmission, driveshaft, rear differential etc.
If the mechanic pulled the driveshaft to inspect it because of the vibration did the vibration get worst or stay the same?
Also to answer your question, I don't really know for sure if my suspension binding could have cause the vibration but I am sure it did not help. Most likely mine were the halfshaft u-joints.
My point was that you really have to inspect everything when the car is jacked up off the ground. I repaired way more than I originally thought the car was going to need.
Also mine felt like the vibration was from the rear of the car not the middle (middle is possibly related to driveshaft or transmission) or the front (front could be engine or flywheel, torque converter).
Good luck and keep us posted!
If it goes away it could be engine related. If it stays which it probably will. It could be transmission, driveshaft, rear differential etc.
If the mechanic pulled the driveshaft to inspect it because of the vibration did the vibration get worst or stay the same?
Also to answer your question, I don't really know for sure if my suspension binding could have cause the vibration but I am sure it did not help. Most likely mine were the halfshaft u-joints.
My point was that you really have to inspect everything when the car is jacked up off the ground. I repaired way more than I originally thought the car was going to need.
Also mine felt like the vibration was from the rear of the car not the middle (middle is possibly related to driveshaft or transmission) or the front (front could be engine or flywheel, torque converter).
Good luck and keep us posted!
Thread Starter
Instructor
Joined: Jul 2012
Posts: 235
Likes: 9
From: Winter Garden Florida
thanks for the ideas. I'm going to try the putting it in nutral when at vibration speed to see if it makes a difference.
I won't get a chance to work on the car till the weekend.
thanks,
John
I won't get a chance to work on the car till the weekend.
thanks,
John
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Pro
Joined: May 2010
Posts: 737
Likes: 3
From: Pennington NJ
I know on my M1028, when we first got it it had a vibration between 37 and 45 MPH. There was a dent in the driveshaft and after it was retubed and balanced, there were absolutely no vibrations at all. Maybe it is your driveshaft?
Will
Will
Thread Starter
Instructor
Joined: Jul 2012
Posts: 235
Likes: 9
From: Winter Garden Florida
update
I have had the time to try all the suggestions here and still have the vibration.
my next move is to replace the tires with BF goodrich comp to see if the tires were the problem.
the next item is to replace the brake rotors when it it comes time to replace the brake pads as i was told that they are a source of vibration also it the get warped with age.
my vibration is not as pronounced as it was so I am going to live with it until I need the brakes. below 65 it is smooth as silk.
I am really enjoying this 28 year old car.
John
my next move is to replace the tires with BF goodrich comp to see if the tires were the problem.
the next item is to replace the brake rotors when it it comes time to replace the brake pads as i was told that they are a source of vibration also it the get warped with age.
my vibration is not as pronounced as it was so I am going to live with it until I need the brakes. below 65 it is smooth as silk.
I am really enjoying this 28 year old car.
John
Last edited by jgalfo; Mar 25, 2013 at 06:27 AM.
Drifting
Joined: Aug 2010
Posts: 1,704
Likes: 8
very interesting the stuff about driveshaft tune,never heard about this...i have the same issue.it's a bad strong vibration in the same range.i'm thinking about an unbalanced driveshaft. it is there any kind of mark in the driveshaft to index this 90 degrees set up?IF someone,pull the shaft without knowing this... no way to set it right again?how can be balanced a driveshaft ?thanks guys
Thread Starter
Instructor
Joined: Jul 2012
Posts: 235
Likes: 9
From: Winter Garden Florida
when I get a chance I am going to try this.
thanks for the suggestion.
John
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Burning Brakes
Joined: Oct 2010
Posts: 1,037
Likes: 28
From: Montclair New Jersey
I had a similiar problem on my 86. It was combination of two things. First my right rear wheel bearing was shot. The second took a little time. After balancing my tires a few times and rotating them also. I finally thought it could be the wheels and it was one wheel was "out of round." I also thought it was my drive shafts or u-joints. I did replace the u-joints anyway while I was looking for the vibration.
Good Luck
Good Luck