I have 1995 4X4 pickup and when I'm on the highway I feel a vibration for about 4 seconds then it goes away for a few seconds then comes back and goes every 5 sec or so over and over. I'm sure it does it at lower speeds but I notice it more at faster speeds.

I don't feel it in the steering wheel so I don't thinks its the tires unbalanced. I feel it more in my body through the seat kind of.

What would cause this vibration to happen for 4 sec then stop for 4 or 5 sec and then do it again and again etc.... I would think it would vibrate all the time if something is wrong?

Any ideas?

Thanks,

 

First, make sure your hubs are not locked. Check the ujoints and output bearing on the transfer. Is it better or worse when accel or decel or while cruising? Cupped or feathered tires can also cause similar symptoms. When 2 very slightly different tones or vibrations occur simultaneously, the wavelengths will overlap at both high points and low points. This is why it will seem to come and go every 4-5 seconds

 

Thanks for the reply.
My brother in law said it might be mud or a rock
On the inside of the tire. When I get home I am going to
Look it over.

 

Driveline imbalance or u-joint angles can do this.
It's hard to describe but at certain rotational speeds, sympathetic (harmonic) vibrations can occur and they will seem to come and go.

A few years back, my father chased down such a demon for 2 years after the car was clipped and spun out onto an "island" divider on the road. The vibration was not a hard vibration, more accurately described lika a rhythmic "fluttering" that came and went between 40 and 60 MPH, but the fluttering was faster at higher speeds and disappeard above 60 or so. After balancing the driveshaft twice and replacing the differential once, what fixed it was replacing the driveshaft and entire rear axle (3rd, brakes and all between) with OEM.

 

i have driven the same 4runner for about 4 years now, about a year ago i noticed that my whole car would shake at about 65-70 mph but it would not shake when i was at city speeds 1-55mph so when I got it checked out by a friend it turned out to be the Cardanic Cross, which means on my yota the shaft was at the point of falling out to the ground,

 

get this checked out immediately it is dangerous if it is loose at all!