Vibration when deceleration at high speed

[DidiDavis]

I recently bought a 1996 explorer Eddie Bauer 4x4. The tires were completely worn out, so I replaced all 4 tires, and had the wheels balanced and the car aligned. I drove it in the highway and noticed a vibration starting at 75-80 mph. The whole car vibrates, but not the steering wheel. I don't know if the car was vibrating before I replaced the tires. Anyways, the vibration gets worst at 85-90 mph (haven't tried faster than that). The weird thing is that it gets worst when I release the gas pedal. Let's say I'm driving at 85 mph, if I'm accelerating, I have this vibration, and when I decelerate (release the gas pedal), it gets worst. I searched in the forum and found a similar issue related to the driveline and rear axle. However, the threads I found state that the vibration gets worst when accelerating, not decelerating.

Below are some things that I thought could be causing the problem. I'd like your ideas before I start going after this.

1- Rear wheel balancing. I don't know if the vibration would get worst when releasing the gas pedal if my rear wheels are out of balance.
2- Front shock absorber worn out. The front ones are really bad. I'll replace front and rear shocks soon.
3- This may sound weird, but could a problem with my engine mounts make the car vibrate??
4- Humm, can't think about anything else.

Any help is appreciated.

Thanks


3-

 

[alohamonte]

Sounds like u have some drag it it decelerates on you.

I'd look at the hubs. They could be stuck in the 4x4 mode meaning ur front driveline spins (adds drag and noise) even if the transfer case is not active.

When u replaced the tires did the shop mention anything about the shocks, front end, or anything like that?

Shimmy at 90... could be anything on an old truck. Shocks, sway bar endlinks, front end joint/bushings, steering rack slop... thats why I keep it below 70.

 

[DidiDavis]

Thanks for the reply.

The shop did not mention anything, 'cause I told them that the front shocks were bad. I will replace the front and rear shocks today and have the wheels balanced again.

Humm, I thought that the hubs were constantly locked to the front axle. The front axle do spin in 2wd. I' don't know if the front shaft also spins, but I guess they shouldn't, right? I'll take a look at it.

Thanks!

 

[DidiDavis]

Well, I took the car in to rebalance the wheels. They were fine, but they did the job anyways. The vibration persists at 75 mph. I haven't had time to replace the shocks today, but I doubt that they are causing this. Since acceleration/deceleration decreases/increases the vibration, I'm betting that I have something going on with my rear drive shaft or rear axle. I have no clue how to identify problems with those parts, though. Should I lift the rear of the car and put in D?