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View Full Version : Shaking at 70mph-80mph



Braff77
06-10-2009, 09:21 PM
So I bought this 92 SC. Got a new tire rod for it.. changed out the Front shocks and got the tires rotated, balance and an alignment.. So my problem is when I get her on the highway and give her a little punch ..The steering wheel starts to shake uncontrollably around 70mph...Then if I let off the gas a little bit then punch it again.. doesn't seem to hardly shake at all:confused:??? I was telling a buddy of mine about this and he seems to think it could be the tires..But the tires are in great shape and seem like they have a lot of life in them..Any help or suggestion would be great!! Thanks in advance..:D

LordBear
06-10-2009, 10:01 PM
sounds like ur tires need to be reballanced.... depending on what shop u go to to have this done can make a difference... they dont all ballance the tires to the same speed..so if ur tire was only ballanced to about 55... after that speed ur tires will no longer be ballanced till u drop back below that speed.

KMT
06-10-2009, 10:13 PM
Did you check your front/rear wheel bearings for freeplay?

Braff77
06-10-2009, 10:18 PM
sounds like ur tires need to be reballanced.... depending on what shop u go to to have this done can make a difference... they dont all ballance the tires to the same speed..so if ur tire was only ballanced to about 55... after that speed ur tires will no longer be ballanced till u drop back below that speed.

I took it to Firestone..Not sure what there speed rating is as far a balancing..But I'm guessing it's the 55mph like you said..that would make sense..Cause she handles just fine up to that point then the Shakies come out..LOL!! I guess I could ask them about this and go from there..Thanks for the help..:) Brian

Braff77
06-10-2009, 10:20 PM
Did you check your front/rear wheel bearings for freeplay?

No..I'll check in to that..:D

birds4us
06-11-2009, 06:51 AM
I have also seen fix a flat cause this. You can balance the tire, but as soon as you do, the fluid inside the tire settles and the tire can be unbalanced again. I would also suggest a thorough suspension inspection and wheel bearing check, front and rear.

Kurt K
06-11-2009, 08:02 AM
Find a place that does "road force" balancing. It's more expense, but can significantly help with balance issues.

SuperCharged91
06-11-2009, 08:51 AM
Also check to make sure your u-joints are tight..... Had something similar happen to me except it was the steering wheel and basically the rest of the front lol ethier way its a easy free thing to check


-Jon

LordBear
06-11-2009, 06:56 PM
um just remembered...when i had my 89 sc....it started getting a shaking problem at freeway speeds....and it was because the tires them selves .. well one or 2 of them any how and they were like new when i got the car..the steel belts were the cause...lower speeds u didnt notice it but at higher speeds i wld start shimmying like a mother...knocked off my rear vew mirror..lol

sinhumane
06-11-2009, 07:28 PM
have you been abusing the drivetrain any? the differential to driveshaft yoke bolts could be loose, mine were and were causing a violent vibration whenever i let off the pedal.

also, check all your lugnuts for tightness... i had another problem that went away when i turned right.... turned out to be loose nuts on the left side.

Braff77
06-11-2009, 08:56 PM
[QUOTE=sinhumane;820124]have you been abusing the drivetrain any? the differential to driveshaft yoke bolts could be loose, mine were and were causing a violent vibration whenever i let off the pedal.

No, not that I'm aware of..I get on it every now in then but not excessive..But I'll look at everything that people suggested on here..Thanks for everyone's input..:D
I'll let you guys know when I find out what it was..Thanks again..:D

BTobiczyk
06-11-2009, 08:58 PM
Like everyone said it is possible it is just a tire balance but it could be a slight out of round of the rim itself. Hit a pothole or anything lately? Sometimes if a car has been sitting a little while it will develop a flat spot on the tire and that will cause it. Just a couple different things to check into there.

talonhead
06-11-2009, 10:15 PM
When you're at speed and hit the brakes, does it get worse? If so might want to check the balljoints for looseness. I've had this happen with my '93 SC and my 4x4 truck.
MikeH