Vibration at 80 MPH - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



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

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 10-23-2019, 06:02 PM
Registered User
 
Join Date: Jul 2014
Posts: 332
Wiki Edits: 0

Thanks: 1
Thanked 17 Times in 12 Posts
Vibration at 80 MPH

I've got a 1968 Camaro with a 350 and a T5 transmission. The motor is "lopey" to say the least. It is hard to say how balanced it is... its no Cadillac for sure. It has Aero 15" steel racing rims and BFG 255/60R15 tires. I had the tires balanced by a shop that had the proper adapter to balance lug-centric wheels.

On the highway, I was getting a very noticeable vibration that started around 70 mph and got stronger (faster frequency feeling) as I crept up to 80 mph in 5th gear. When I gripped the shifter ball tightly it felt like I was holding onto an poorly balanced orbital sander .

Test 1
I jacked the rear up and put it on jackstands and spun the tires up to 80 MPH in 5th gear... same vibration.

Test 2
Then I took the wheels and drums off the back and spun it up again... same vibration.

Test 3
Then I took the driveshaft out and spun it up again... I still had a vibration but it wasn't nearly intense. When I tightly gripped the shifter ball the vibration goes away. This time the vibration is not unlike what I feel when I rev the engine in neutral.


So it is probably my driveshaft and/or U joints? Dang thing is that I just had that driveshaft built new back in 2016. And they balanced it. Seems like a real reputable shop so I trusted their work. When I first got the car on the road in 2016 it had the vibration but I attributed that to the fact that the tires weren't balanced. Right now it has less than 500 miles on it for sure. I plan on calling them tomorrow and see if I can negotiate them to look at it for free. Driveshaft still has their sticker on it and looks new!!

I think I've got my pinion angles right. The engine/transmission is 2 degrees sloped down (front to back). The rear end is pitched up by 3 degrees. So the pinions are parallel with each other (+/- 1 degree).


Any thoughts or suggestions? If I bring them the driveshaft and they put it on the balancer and tell me it is already balanced.... then what would you suggest?



Thanks,
Sal

    Advertisement

Last edited by ssanto; 10-23-2019 at 06:14 PM.
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 10-23-2019, 06:25 PM
big gear head's Avatar
High Performance Rear Ends
 
Join Date: Nov 2009
Location: Central City, KY
Posts: 3,477
Wiki Edits: 0

Thanks: 78
Thanked 1,705 Times in 1,285 Posts
If they used thin tubing like an OEM drive shaft then the shaft is bending at high RPMs. This is very common. Most shops only do a low speed balance, so this problem doesn't show up when they balance it. An aluminum drive shaft is much less likely to do this. You can also increase the tube diameter 1/2 inch and it may fix the problem. Thicker tubing also works better.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 10-23-2019, 06:32 PM
Registered User
 
Join Date: Jul 2014
Posts: 332
Wiki Edits: 0

Thanks: 1
Thanked 17 Times in 12 Posts
Quote:
Originally Posted by big gear head View Post
If they used thin tubing like an OEM drive shaft then the shaft is bending at high RPMs. This is very common. Most shops only do a low speed balance, so this problem doesn't show up when they balance it. An aluminum drive shaft is much less likely to do this. You can also increase the tube diameter 1/2 inch and it may fix the problem. Thicker tubing also works better.
In 5th gear around 80 MPH it the driveshaft is spinning at 3500-4000 RPM. Is that "high speed"?

OK so I lied a little about the "new" driveshaft. It is really whatever driveshaft that was in the trunk of the car when I got it which I believe to be original from 1968. It is 2.5 inch diameter. I had them cut it down and put a new yoke on it and balance it.
Reply With Quote Quick reply to this message
 
  #4 (permalink)  
Old 10-23-2019, 06:51 PM
chasracer's Avatar
True Hotrodder
 
Join Date: Oct 2018
Posts: 610
Wiki Edits: 0

Thanks: 41
Thanked 140 Times in 124 Posts
Yea but the pinion angle deal is probably the culprit. As you said you have a 1 degree deflection - sitting on jackstands, a jack or sitting on the garage floor? And what is that angle when going down the road - front end lower or higher? Rear end settling downward maybe - that's changing that angle. You may want to modify that angle with some wedge plates between the rear housing and springs. But I would check it at rest, then see what happens as you raise or lower the front or rear of the car.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 10-23-2019, 07:57 PM
Registered User
 
Join Date: Jul 2014
Posts: 332
Wiki Edits: 0

Thanks: 1
Thanked 17 Times in 12 Posts
Quote:
Originally Posted by chasracer View Post
Yea but the pinion angle deal is probably the culprit. As you said you have a 1 degree deflection - sitting on jackstands, a jack or sitting on the garage floor? And what is that angle when going down the road - front end lower or higher? Rear end settling downward maybe - that's changing that angle. You may want to modify that angle with some wedge plates between the rear housing and springs. But I would check it at rest, then see what happens as you raise or lower the front or rear of the car.
I measured the angles with the car sitting on its wheels like normal. I get the vibration when it is rolling down the road at 80 MPH in neutral so there is no load on the rear end that would change the angle.

You think 1 degree of difference is that big of a deal?

But I get your point. I can test different angles while it is at rest to see if that helps the vibration. I recall shimming the transmission mount with washers so I should be able to very easily play with things on that end.
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 10-23-2019, 08:18 PM
big gear head's Avatar
High Performance Rear Ends
 
Join Date: Nov 2009
Location: Central City, KY
Posts: 3,477
Wiki Edits: 0

Thanks: 78
Thanked 1,705 Times in 1,285 Posts
Yes, 3500-4000 RPM is high speed for a drive shaft. 2.5 inches is small.
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 10-23-2019, 08:35 PM
ericnova72's Avatar
More for Less Racer
 
Join Date: Jan 2007
Location: S.W. Lower Michigan
Age: 52
Posts: 17,627
Wiki Edits: 0

Thanks: 271
Thanked 3,191 Times in 2,679 Posts
Quote:
Originally Posted by big gear head View Post
Yes, 3500-4000 RPM is high speed for a drive shaft. 2.5 inches is small.
And stock driveshaft is crap, seamed wall material that is basically the same stuff as muffler tubing, and factory standards for concentricity of tube and yokes(straightness0 is not very good. I went through this with my '72 Nova, which has the same shaft you're dealing with.

I also found that stock rear pinion yoke on the rear end are not very concentric to the spline either....I had to check 5 factory yokes from the junkyard to find one with less than .015" run-out at the U-joint cups.

Get a real performance driveshaft made....Denny's Driveshaft, Inland Empire Driveline, Mark Williams, Strange, Coleman.

Most local shop can't make a good enough new shaft either, they are used to making low speed 3000 rpm truck shafts
Reply With Quote Quick reply to this message
The Following User Says Thank You to ericnova72 For This Useful Post:
big gear head (10-24-2019)
  #8 (permalink)  
Old 10-23-2019, 08:39 PM
techinspector1's Avatar
Member
 
Last wiki edit: DynoSim combinations
Join Date: Oct 2005
Location: Zephyrhills, Florida, USA
Age: 77
Posts: 16,954
Wiki Edits: 326

Thanks: 1,915
Thanked 2,813 Times in 2,107 Posts
Yep, Denny's on the east coast, Inland Empire on the west coast. I haven't used the others that Eric posted.
https://www.iedls.com/
https://www.dennysdriveshaft.com/
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 10-23-2019, 09:11 PM
Registered User
 
Join Date: Jul 2014
Posts: 332
Wiki Edits: 0

Thanks: 1
Thanked 17 Times in 12 Posts
Well... the place was called Inland Truck Parts

I'll give them a call tomorrow and ask what RPM they balance at. Maybe give them some feedback... seems that they should know enough to tell me that what I asked for may not be the best thing.
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 10-24-2019, 05:57 AM
ericnova72's Avatar
More for Less Racer
 
Join Date: Jan 2007
Location: S.W. Lower Michigan
Age: 52
Posts: 17,627
Wiki Edits: 0

Thanks: 271
Thanked 3,191 Times in 2,679 Posts
Quote:
Originally Posted by ssanto View Post
Well... the place was called Inland Truck Parts

I'll give them a call tomorrow and ask what RPM they balance at. Maybe give them some feedback... seems that they should know enough to tell me that what I asked for may not be the best thing.
Just a little more info...

If that stock shaft wasn't very straight to begin with, it won't matter how good they balance it, it will still reach a harmonic point and vibrate....changing the rpm it is balanced at and the amount of weight ust moves the vibration rpm higher or lower.

a straight shaft, like I got from Denny's years ago, will need no weights to be balanced....if it is straight and made from Dom(drawn-over-mandrel) tubing that has a consistent wall thickness it will have no heavy side and need no weights.
First thing I noticed when I opening the box was there was no weights on the shaft, and I was instantly pissed, thought I was being ripped off or someone screwed up....one call to Denny's explained the situation, that a straight shaft won't need some offset weight added to it , it will be balanced all on it's own.

He was dead right, and that's how I found out my stock factory 8.5" 10-bolt rear pinion yoke was off by almost .055"....I put his new shaft in the car, and started checking run-out at each ends, just inboard of the tube weld....front was less than .007", just like he said it should be, rear was out a mile. All due to the factory machining tolerance on the u-joint cups on the pinion yoke.
if I run into that situation again, I'm just going to buy a forged or billet yoke from Mark Williams or similar.

If you've got a dial indicator and magnetic base, check your shaft runout at the front, center, and rear....anything over .015" is going to give you problems .

by the way, that factory Camaro shaft should be 3" seamed tubing, not 2.5"...if it actually is 2.5" it came from something else, someone must a swapped it at some point. The '78-87 G-body, the Metric chassis(Monte Carlo, El Camino, Malibu, Cutlass, Grand Prix/LeMans, Regal) did use a very light duty 2.5" shaft ,might have come from there.
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 10-24-2019, 07:37 AM
chasracer's Avatar
True Hotrodder
 
Join Date: Oct 2018
Posts: 610
Wiki Edits: 0

Thanks: 41
Thanked 140 Times in 124 Posts
Quote:
Originally Posted by ssanto View Post
I measured the angles with the car sitting on its wheels like normal. I get the vibration when it is rolling down the road at 80 MPH in neutral so there is no load on the rear end that would change the angle.

You think 1 degree of difference is that big of a deal?

But I get your point. I can test different angles while it is at rest to see if that helps the vibration. I recall shimming the transmission mount with washers so I should be able to very easily play with things on that end.

It's just that 1 degree is really close to zero and we all understand that universals running in a zero plane are going to cause an issue. I see others are questioning the driveshaft rebuild. I would talk with any local racers or speed shops that you can and see who they use in the area. We had a shaft built for our bracket Camaro at some other place and it was nothing but trouble. Checked around and people say go see Johnny at Standard Parts in Richmond, VA - yep he's the guy! We have multiple racecars and every one of the shafts is his build - no issues.
Reply With Quote Quick reply to this message
  #12 (permalink)  
Old 10-24-2019, 04:03 PM
Registered User
 
Join Date: Jul 2014
Posts: 332
Wiki Edits: 0

Thanks: 1
Thanked 17 Times in 12 Posts
I measured the runout on the driveshaft with a dial indicator...

Rear end -- 0.020
Center -- 0.023
Front -- 0.039

The rear end has a new pinion yoke.

I put the gauge on the slip yoke in the transmission and got 0.0015 runout.

Last edited by ssanto; 10-24-2019 at 04:20 PM.
Reply With Quote Quick reply to this message
  #13 (permalink)  
Old 10-24-2019, 05:31 PM
Registered User
 
Join Date: Jul 2004
Location: At Speed
Age: 56
Posts: 2,976
Wiki Edits: 0

Thanks: 321
Thanked 424 Times in 374 Posts
about 0.010 inch is the Max at each end, 0.015 inch in the middle.

I had a shaft from Inland Empire that came in a kit with a tremec trans, it vibrated bad so I had it balanced which made it better but still to much, had to get a new shaft
Reply With Quote Quick reply to this message
  #14 (permalink)  
Old 10-24-2019, 06:42 PM
big gear head's Avatar
High Performance Rear Ends
 
Join Date: Nov 2009
Location: Central City, KY
Posts: 3,477
Wiki Edits: 0

Thanks: 78
Thanked 1,705 Times in 1,285 Posts
It may be perfectly straight when turning it by hand, but warped at high RPMs. You have a thin wall, small diameter stock drive shaft that is turning faster than it was designed to turn. I can't guarantee that this is your problem, but I'm 90% sure that it is. A thick wall larger diameter shaft will most likely fix the problem. I've seen this too many times. People will remove a 3.08 gear and install a 3.73 or 4.10 with an over drive transmission and then suddenly they have a vibration that they try to blame on the rear end or transmission, when the only problem is the stock drive shaft that is now turning too fast and warping at highway speed.
Reply With Quote Quick reply to this message
  #15 (permalink)  
Old 10-24-2019, 06:49 PM
Registered User
 
Join Date: Jul 2014
Posts: 332
Wiki Edits: 0

Thanks: 1
Thanked 17 Times in 12 Posts
Quote:
Originally Posted by big gear head View Post
It may be perfectly straight when turning it by hand, but warped at high RPMs. You have a thin wall, small diameter stock drive shaft that is turning faster than it was designed to turn. I can't guarantee that this is your problem, but I'm 90% sure that it is. A thick wall larger diameter shaft will most likely fix the problem. I've seen this too many times. People will remove a 3.08 gear and install a 3.73 or 4.10 with an over drive transmission and then suddenly they have a vibration that they try to blame on the rear end or transmission, when the only problem is the stock drive shaft that is now turning too fast and warping at highway speed.

I bet that is the problem too. I was just saying that the 0.040 runout may be too much in itself causing the vibration.
Reply With Quote Quick reply to this message

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:
Insurance
Please select your insurance company (Optional)

Log-in



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 02:58 PM.


Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.