I have a vibration between 65-80 MPH that varies with road conditions. I had the tires (General Ameritrac) balanced and the vibration did not change. Thought it may be shocks, so I pulled the lower mount on each one and they still sprung out like a new shock, which leads me to believe that they could still be good. I have 54K on this Expedition and from what I have read here that is the limit for shocks.
Could the damping part of the shock still be bad and the shock still spring apart?
If not shocks, then what else could it be?

 

Jump up and down on your rear bumper. If the truck continues to bounce after you stop jumping then the shocks are probably shot. Like you mentioned, with 54K miles, you're pushing the limits anyway.

 

I had a low frequency rumbling at 65-75 mph that turned out to be the drive shaft. Do a search on rumbling and you should see a buch of issues that the guys have gone through. Mine felt like it was coming throught the floor boards somewhere in the second row.

Another thing that I did to get rid of general vibration and coarsness was to get rid of the General Tires; They are absolute junk. I jacked the truck up and spun every tire to find that all were out of round, even the spare.

I have a '00 2x EB 5.4 and those Generals were awful in the rain. They had only 20k miles on them at the time from the previous lease return owner, and they looked like gentle miles because they looked new still. I start thinking that I'm looking at $5-$600 in tires.

So I visit the tire guy I've been doing business with for the last 20 or so years and he says that he can sell me another set of Conti-Gens for 75 bucks a piece. But the tire I should be interested in was a set of Michelin CrossTerrains at a buck seventy-five a piece. And do I want to change them all. Woa, buddy, run that by me againn one was seventy-five and the other was a buck seventy-five.

He explianed to me that if you put okay tires on a passenger car and you get a blowout it no big deal; you pull off the road and toss the spare on. But on a big SUV many things can go wrong that could spell disaster. Heat, he says, spell failure. And the Michelins are rounder and truer than almost any other tire, form the day you buy em the the day you replace them. And that they run cooler from the roundness and all the other engineering they put in them.

Okay okay I'll sell the house so I can have good tires. He was only slightly amused. I blow off salesmen everyday when they pitch me hard but this guy is quiet and serious, plus I've dealt with him for over 20 years. So it was a hard decision but I eventually plunked down my almost 800 big ones for a set of Michelins.

An guess what, he was right; it really was night and day. Vibration, harshness, squirm, bouncyness, thwap and hum were all gone. the Generals were quiet, but hey had a low frequency hum and a high frequency hiss and they shook and gluggled over bumps. Sometimes I wonder if a Lexus LX450 is this good. I do a fair amount of camping so I spend a small portion off pavement on groomed but weather rutted trails. These are absolutely not offroad quality but they do have a confidence that the Generals lacked.

So getting back to your problem, ballancing was a good start but you need to check roundness and trueness. If that checks out, then have your driveline and tranny inspected. There are a lot of posts from guys saying that a double flush of their tranny cured a rumbling or judder.

Remember that engine ballance or vibrations are RPM related while drive-line issues are speed related. The tranny however can be both depending on input and output side.

Happy hunting and I hope this has been helpfull.

SurfinMutt

 

First, thanks for the input guys.
Here's my thought process.....
I can put the tranny in N going about 75MPH and the vibration still exists, so it has to be either shocks, tires, brakes, axle (not likely) or driveshaft. The u-joints are tight, so who knows....... I have jacked the vehicle up and spun the tires. How much is too much out of round? They looked pretty concentric, but there was some movement. Applying the brakes does not change the vibration, so brakes can be ruled out. That leaves the shocks and tires. Tires are like brand new, so they are going to have to stay on. Still had the nipples on them when I bought the truck 2k miles ago. If the tires were out of round then it would vibrate all of the time no matter what the condition of the road was. The vibration is much worse on older roads or back roads. But the shocks still rebound when tested!!! That is why I am puzzled. I may just try some new shocks!

 

Eric, installing Rancho shocks on my Expy a couple years ago was the best thing I've done to date (the chip is a close second). I can't believe the amount of stability this beast exhibits even with over-size tires.

 

Another area to check is your wheel alignment. too mcuh toe in can cause tire scrubbing which sometimes feels like a front end vibration. Just a thought.

Pbfoot

 

Eric,

I had a very similar problem just after I had tires installed - vibration at about 70+ MPH. Tire balance checked just fine. The tire tech looked closely at the tire on the balance machine and noticed it had a 'hop' in it - it was visually out of round. He ordered 2 new tires no charge - problem solved.

I know some tire dealers are challenging to get good customer service from past the routine rotation and flat repair. That is why good customer service is important to me.

Eric
00 Expy 4x4

 

Cheaper tires are frequently out of round. Even good tires that have been sitting in a rack for five years or more are now permanently out of round and dangerous to use at high speed. Check the date on your tires and if newer than two or three years old, consider it the tires being cheaply made. If you drive much at all, or do any high speed driving, see if you can get those replaced by the dealer, or move upa grade. Paying more now for tires will pay off in the long run with less suspension wear, less frustration for you, and greater safety for you and your passengers. A $250,000 Ferrari and your vehicle have one thing in common: everything comes down to where the rubber meets the road.