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I need your help, badly!

  • Thread starter Thread starter 68stang351
  • Start date Start date Jun 19, 2007

68stang351

Founding Member
May 16, 2002
850
9
39
Savoy TX
Jun 19, 2007
#1
  • Jun 19, 2007
  • #1
Ok, for about 4 years now I've had this annoying shake. I'm hoping someone can help me because I'm really getting tired of it. I will present you the facts.

It only happens between about 65-85 mph, and only when I'm coasting or maintaining a steady speed. If I'm on the throttle it doesn't do it.

It started happening after I replaced all of my front suspension and changed the rear end. I did all of it at the same time. (It was a 6 cyl., so I put a 8" in). I've ruled out the driveshaft, because I've used 4 different driveshafts in it and it still does it. I've even bought another trans crossmember and mount. I've had all wheels/tires balanced.


I should note that I've never had the front end aligned, however the car goes down the road straight. So I guess it could be coming from the front.
I'm not sure if its in the front or the rear, but I'm thinking it's the rear.
The whole car shakes horribly.

I think that maybe I have a pinion angle issue. I think this because that it only does it when I'm not on the throttle. From my thinking, the pinion angle is acceptable when the rear is slightly turned from applying the power, but when I let off the gas, and the rear is no longer applying power, that it settles back into a bad angle. Am I correct in this being a possibility?

I'm also questioning the engineering integrity of my traction bars. They are the kind that have the u bolt/shock mounting plate welded to the traction bar. It looks homemade. I'm wondering if that could cause the problem.

Should I have the pinion angle checked?
Should I have the front end aligned?
Or can you think of something else it might be?

I really need help with this, it's making the car no fun to drive.
I appreciate any advice.:SNSign:
 
D

D.Hearne

New Member
Sep 29, 2000
11,730
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0
south louisiana
Jun 19, 2007
#2
  • Jun 19, 2007
  • #2
It ain't the traction bars. My Lakewoods are built the same way. And they're not cheap pieces. Could be a pinion issue or the tailshaft bushing in the transmission tailhousing is worn out. Could also be bad tires, does the frequency of the vibration correlate to the driveshaft rotation or the wheel's rotation (wheel rotation is slower than the driveline)
 

HistoricMustang

Active Member
Apr 11, 2003
2,359
0
46
Confederate States of America
Jun 19, 2007
#3
  • Jun 19, 2007
  • #3
D.Hearne said:
It ain't the traction bars. My Lakewoods are built the same way. And they're not cheap pieces. Could be a pinion issue or the tailshaft bushing in the transmission tailhousing is worn out. Could also be bad tires, does the frequency of the vibration correlate to the driveshaft rotation or the wheel's rotation (wheel rotation is slower than the driveline)
Click to expand...

"D", lets throw in "U" joints?

HistoricMustang
 

68stang351

Founding Member
May 16, 2002
850
9
39
Savoy TX
Jun 19, 2007
#4
  • Jun 19, 2007
  • #4
It's definitely not u joints. I've used many different sets with many different driveshafts.

The tires are M/T Drag Radials, only about 1.5 years old, it still shook before them, as well as when they were new.

does the frequency of the vibration correlate to the driveshaft rotation or the wheel's rotation
Click to expand...

I just went and drove it and payed close attention to what it did.
It shakes at the same speed no matter what gear i'm in (3rd, 4th, 5th). So I guess that would be wheel rotation.

It doesn't shake at all if I'm in the throttle. But if I maintain speed, it shakes. If I coast w/ no throttle, it does it the worst.

Thanks!
 
D

D.Hearne

New Member
Sep 29, 2000
11,730
6
0
south louisiana
Jun 19, 2007
#5
  • Jun 19, 2007
  • #5
68stang351 said:
Kinda hard to say, it feels more like driveshaft, but it does it at the same speed no matter what gear i'm in (3rd, 4th, 5th), so that tells me its wheel rotation.
Click to expand...

Driveline vibes will be the same no matter what gear you're in. Any set speed will be the same driveline rpms, no matter the gear the transmission's in.
 
D

D.Hearne

New Member
Sep 29, 2000
11,730
6
0
south louisiana
Jun 19, 2007
#6
  • Jun 19, 2007
  • #6
HistoricMustang said:
"D", lets throw in "U" joints?

HistoricMustang
Click to expand...

I agree..................But only he can feel what's going on.
 

68stang351

Founding Member
May 16, 2002
850
9
39
Savoy TX
Jun 19, 2007
#7
  • Jun 19, 2007
  • #7
I edited my last post, but not before you replied. You might not have seen the edited post. I went and drove it.

What I meant was the going a set m.p.h., it shakes at the same frequency no matter what gear I'm in.
Thanks. I think we'll get it figured out.
 

rbohm

Founding Member
Apr 12, 2002
6,698
550
204
tucson,az
Jun 19, 2007
#8
  • Jun 19, 2007
  • #8
68stang351 said:
It's definitely not u joints. I've used many different sets with many different driveshafts.
Click to expand...

u-joints dont have to be bad to cause a vibration. if they are installed incorrectly they can be slightly offset which will cause a vibration.

something else to check is the brake drums and rotors. if they are out of balance you get a vibration. this can be checked with the tires on the car. i forget the name of the machine used.

one last thing to check after you have looked at the above items. ok two last things;

1: look for a bent wheel
2: check to make sure the tires are round. i have seen tires out fo round enough that you could actually see it when the tire was spinning on the balance machine. tires can be trued by trimming the tread on a lathe.
3: check for a bent spindle(ok i lied again )
 

stangman67

Member
Feb 8, 2003
294
0
17
connecticut
Jun 19, 2007
#9
  • Jun 19, 2007
  • #9
I have just been through this issue too. I found my pinion angle was the issue. My trans angled up 4 deg, and the pinion nose at 2 deg down. I replaced my rear first off after 4 years of dealing with the vibes, and it was still there afterwards. I bought some 4 deg shims for the spring perches, and it is now smooth. I couldnt believe it when I did it, because my other rear that was only 5 years old was good. It was all in the angles. You want the trans angle to be equal, or possibly 1-2 deg down from the trans, so when the pinion rotates up under load, they are equal.
 

2nd Mustang

Founding Member
Feb 24, 2002
2,488
0
46
Southern California
Jun 19, 2007
#10
  • Jun 19, 2007
  • #10
How about running the car on jack stands or on a dyno roller? It may help separate front from rear issues.
 

68stang351

Founding Member
May 16, 2002
850
9
39
Savoy TX
Jun 20, 2007
#11
  • Jun 20, 2007
  • #11
2nd Mustang said:
How about running the car on jack stands or on a dyno roller? It may help separate front from rear issues.
Click to expand...

I've ran it with the rear on jack stands, it shakes so bad I'm afraid it will fall off.
 
6

68RCodeConv

New Member
Oct 2, 2003
345
0
0
Houston, TX
Jun 20, 2007
#12
  • Jun 20, 2007
  • #12
Put it back on the jack stands. Remove the rear tires. Install a couple of lug nuts to hold the brake drums in place. Run the car up and see if the vibration is still there. Then remove the brake drums. After doing so DO NOT STEP ON THE BRAKES AT ALL. Run the car up and see if the vibration is still there. Let it coast down - DO NOT STEP ON THE BRAKES.

If the vibration is still there you almost certainly have a pinion angle problem.

Good luck. I have a vibration and I have done everything you have done and I have shimmed the the pinion up twice (4 degrees and then 6 degrees). Still have the vibration.
 

65fastbackresto

Active Member
Apr 13, 2007
1,229
7
39
AR
Jun 20, 2007
#13
  • Jun 20, 2007
  • #13
Axle bearings?

Just a guess.
 

68stang351

Founding Member
May 16, 2002
850
9
39
Savoy TX
Jun 20, 2007
#14
  • Jun 20, 2007
  • #14
68RCodeConv said:
Put it back on the jack stands. Remove the rear tires. Install a couple of lug nuts to hold the brake drums in place. Run the car up and see if the vibration is still there. Then remove the brake drums. After doing so DO NOT STEP ON THE BRAKES AT ALL. Run the car up and see if the vibration is still there. Let it coast down - DO NOT STEP ON THE BRAKES.

If the vibration is still there you almost certainly have a pinion angle problem.

Good luck. I have a vibration and I have done everything you have done and I have shimmed the the pinion up twice (4 degrees and then 6 degrees). Still have the vibration.
Click to expand...

Thanks, I will definetely try that.

As for axle bearings, I put new ones in before I put the rear in the car.

And thanks for everyone's help!
 

68stang351

Founding Member
May 16, 2002
850
9
39
Savoy TX
Jun 23, 2007
#15
  • Jun 23, 2007
  • #15
Okay, I tried 68RCode's suggestion. Even with the drums off it still shook. Not near as bad as when it was on the road though.

I could tell no difference in the shake with drums on vs. drums off.

Pinion angle? I have some 2 degree plates I guess I'll put on if I can ever find them. I bought them 4 years ago before we moved.
 

68stang351

Founding Member
May 16, 2002
850
9
39
Savoy TX
Mar 13, 2011
#16
  • Mar 13, 2011
  • #16
rbohm said:
something else to check is the brake drums and rotors.
Click to expand...




WOW! I feel stupid now!!!

I never looked at the drums. I decided to put my Bullitt wheels on yesterday and for some reason only just now noticed that one drum has a weight on it and one doesn't. I went and put a new pair of drums and I now have no vibration at all.

What an idiot! It only took me like 8 or 9 years to figure it out when it was something so simple, and someone even suggested it!
 

tx65coupe

Active Member
Nov 29, 1999
1,551
1
37
Mar 16, 2011
#17
  • Mar 16, 2011
  • #17
Thats cool that its fixed now.
 
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