98 nissan pathfinder gets very unstable over 70mph


Old 05-02-04, 07:33 PM
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98 nissan pathfinder gets very unstable over 70mph

I have a 98 pathfinder with 107k on it. If I drive it over 70, it starts to veer all over, almost like something rocking the truck side to side very hard. Very scary. If I don't slow it down the truck would just roll it's so bad. It shows normal tire wear and it doesn't do it under 70. Would a bad strut cause this. I think something in the suspension is bad, but I don't see anything broken. I got under the truck and nothing seems to be missing, lose, or broken on the front and the rear of the truck.
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Old 05-03-04, 04:41 PM
Join Date: Apr 2002
Location: Pittsburgh,Pa
Posts: 2,417
Sounds like you need to get the vehicle in the air and checked very closely.Shocks and or struts could be bad at that mileage.You may also have worn bushings.You can bounce the truck on each corner and see if it bounces more than 3 times the shocks are bad.
Old 05-04-04, 07:20 PM
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I checked the bounce effect on the corners. They are all even. It handles fine at slower speeds. I can pull the wheel from side to side at 50mph or so and it's fine. Just when I cruise at 70 or so it feels like something is pushing the truck back and forth harder and harder if I stay on the gas. It goes away after I slow down. Then comes back @70mph.
Old 05-06-07, 09:20 PM
Join Date: May 2007
Posts: 5
Talking unstable over 70.

All vehicles have a natural resonant frame frequency. This natural resonance usually occurs around the mid sixity mph up to higher speeds. You have a tire in front and one in back ( on each side), and they begin to go up and down bending the frame, usually the suspension dampens out this resonance, but it will always peak at the specific resonant speed. Moving away from the resonant speed will cause the frame frequency to move from the resonant frequency, so speed up or down to stop the gyrations. Of course increasing speed has its own particular hazards. Balancing wheels will also help reduce the wheel "hopping. " That's about all I remember from my Mechanical engineering "Statics and Dynamics"

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