Harmonic vibration at hwy speeds in 97 Ford Explorer

[jmden]

I realize this may be a bit off the topic of long range hunting, but I do use this rig to hunt, so there is a connection and I have a feeling there's a few guys hanging out here that might have some ideas if they are willing to take a stab at it. Len, delete this if it's out of line.

I've got a 1997 Explorer 4WD with a harmonic vibration that starts at 65mph and goes up as far as I've taken it. Typically at hwy speedds, it lasts for about 5 seconds then goes away for 3-4 seconds, then comes back in that cyclical fashion. I can feel it in the seat and some in the steering wheel, but I think that's (steering wheel) just because it's strong enough to feel it in the entire car.

I did not recall noticing this until I purchased new Toyo Open Country 6 ply A/T tires last fall after blowing one of the same tires (about at the end of their life) on a trip that entailed 200 miles of nasty gravel roads on northern Vancouver Island. There were just a few feet on the aluminum rim til I stopped. Les Schwab has checked and double checked the rims alone. The other day (their suggestion, not mine) they gave me a complete set of new tires as they had found a little treadwell seperation in on the year old tires and the vibration was less, but still there.

I recently had the upper control arms replace and had a new C/V joint replaced. Front sway bar bushings are just about 2 years old. 2 garages say there is nothing wrong with the front end or wheel bearings etc. Lower ball joints are new 2-3 years ago. It's been aligned 3x over the past year.

This happens at a certain speed (65mph and above) over the ground so it's got to be txfer case output shaft or back from that. Local Ford garage said that the txfer case output shaft is good and tight. U-joints all check out good. Driveshaft out of balance? Something in the rear diff?

 

[royinidaho]

Hey, I'm all over this one!!

This is evidence a cyclic resonance harmonic vibration between two vehicle components.

They had a similar problem with the F-32 fighter. Their problem was when both engines were at the exact RPM there was no vibration. However when one or the other of the engines oscillated in RPM, which one usually did, the vibration would occur. Thus vibration, no vibration then vibration over and over again until they dropped below Mach I.

Your solution would be to weld the rear differential so that both wheels on always rotated at the same exact RPM.

If you buy into this you're as goofy as me.

Oh, I just dreamed up that F-32 stuff too.

However, I would give rotating those tires around and see what happens.

Those kinds of things drive a fella nuts.

I have a "click" showing up in the left front of my 01 Chev 1500. The farther away from home the more I think about it.

Keep lookin' you'll find it....

Cheers

Roy

 

[SidecarFlip]

The click is because it's a Chevy. Thats Obama rattling around under the hubcap.

It's the agressive tread pattern setting up the vibration. Swotch to a rib tread tire and it will disappear.

I run 31 x 10.5 x 16's on my F350 4x4 in Goodyear All Terrain KO/KD's and the tread design (agressive) causes some vibration, I ignore it.

 

[HARPERC]

I'm with Roy, when you start forgetting things, don't get stressed just start remembering it wrong. Way more fun any way.

I've had a driveline give similar grief, but I think Sidecar, might have it pegged with the tire tread. Or it's a little of this and that, that's going to be a bitch to solve.

 

[bigngreen]

Turn the radio up!

 

[jmden]

And here I thought I'd get experts to pinpoint the problem! What was I thinking?

Yeah, roy, running two engines at once whether in a plane or boat, there is definitely a sweet spot you can hear!

 

[jkupper]

Turn the radio up!

That's funny right there, I don't care who you are

 

[shorty]

Had a similar problem wiyh my F250...it turned out it was a stuck trunnion on the U joint in front of the carrier bearing. We didn't find it till we took the driveline completely out,also replaced carrier bearing since we had it out. my .0002 anyway.
+1 on the radio...Marshall Tucker Band and crank it up!

 

[jkupper]

+1 on the radio...Marshall Tucker Band and crank it up!

Preferrably "Fire on the Mountain" or "Heard it in a Love Song"

 

[SidecarFlip]

Ford has some 'better ideas' like no grease trunions (U-joints) and other stuff, so does Chevy and Fiat-Chrysler, not just Ford. It's all about making it as cheaply as possible and selling it for the most profit, the American way.....

I still believe it's the tires but I'd be replacing the trunions anyway with Super U-Joints. They have a grease zerk.

I had to replace the upper and lower ball joints on my F350 (solid axle Dana 60) in the first 30,000 miles because they aren't greasable from the factory and they got wonky... Not a big deal, just time consuming. All have zerks now. Still a PITA to grease the uppers as there isn't sufficient room to leave the zerk in the upper without the axle trunion wiping it off, so it's a pull the plug, screw in a zerk, grease and remove and replace the plug.

Ford also puts a viscous dampener on the rear propeller shaft that sometimes gets wonky and that will set up a vibration as well. Problem is, thats a driveline specialist replacement as it's pressed on the propeller shaft. I'm on my 3rd carrier bearing in 90K miles. At least Ford sees fit to apply super slide blue to the splines.

It's nice owning a machine and fabrication shop. I replaced every suspension spring pivot with roller bearings and cross drilled securement pins with grease fittings and flipped the front springs so the swing shackle is in the rear instead of the front.... Ford did that on subsequent Super Duty trucks, must have looked at mine...lol Still rides like a lumber wagon, it's a one ton so I don't expect a Caddilac ride but at least you can drive down the road without things flying around in the cab.

One thing I forgot to mention is that you have to 'time' the driveline if you remove any component for replacement/rebuilding. The easiest way is to pre-mark each section with a paint marker so when you reinstall it, you can line everything up. If you don't, it will vibrate at speed. If you had it apart and never marked it, it's easy to tell if it's 'timed' by looking at the position of each trunion. Each trunion starting from the back differential has to be at a 90 degree relationship to the next one (looking at the outer knuckles). They can't run parallel, they will vibrate. opposing knuckles cancel any imbalance.

Finally, make sure the weight tab is on each section. There will be a spot welded on weight tab on each tube from the factory and when working on a drive shaft, it's easy to knock it off. If it's gone, the driveline will vibrate. If it is missing, you'll have to have that section harmonically balanced at a driveline shop.

Keep in midn that if you have say, a 3.55-1 final drive, that driveline is turning 3.55 revolutions to turn the tires 1 revolution. That baby (driveline) is whipping around under there at 65 per.

I just muddied the water a bit.....

 

[jmden]

Thanks, SidecarFlip. I went to a driveline specialist in town today who drove it and thinks it's the u-joints. 180K with original, non greasable, u-joints. I've replaced Ford u-joints in the past and have thought to my self that the reason I'm replacing this is because it was non-greasable...arrgghh. They'll pull the driveline Monday and go through everything. I've thought about u-joints for a year, but 2 garages have told me they are fine. A specialist has a little different take on things, however.

You have done some serious work on that 350. Pretty cool to be owner of a shop and do that stuff.

 

[Wile E Coyote]

a thought on U-joints with and without fittings from recent experience;

My Chevy blazer (02) had rear drive U-joints replaced last fall after approximately 245k miles on the OEM parts. We used the type with grease fittings as replacements. They were done (worn out) by June. In their short life they were greased twice; once upon installation and again in the middle of the winter during a oil change and lube.


When the failure happened in June, naturally, I wasn't anywhere near home. But the repair station a block away from the breakdown was a 4WD and off-road specialty shop. They used fitting-less U-joints to effect the repair.

When I questioned the selection and the owner of the shop showed me several of the vehicles in the yard, all had fitting-less U-joints. Some of these vehicles were road worthy and others were strictly off road. All were considerably more heavy duty than my little Chevy. Chris' explained to me that the Zerk fitting that allowed the U-joint to be greased also allowed dirt and water to infiltrate thereby accelerating the next failure. This could be avoided, or at least minimized by weekly lubrication BUT who's gonna' do that?

A buddy had a similar situation with his Dodge 3500. He does a lot of towing with a construction trailer too. The cheap parts failed in weeks. The better parts lasted longer but still failed in a month or two. Then he replaced with fitting-less and that was 2 years ago. still going.

jmden, ask your driveline guy about this if the work hasn't been done yet.

Pete

 

[jmden]

Good point. I'll make sure and look into that. Thanx.

a thought on U-joints with and without fittings from recent experience;

My Chevy blazer (02) had rear drive U-joints replaced last fall after approximately 245k miles on the OEM parts. We used the type with grease fittings as replacements. They were done (worn out) by June. In their short life they were greased twice; once upon installation and again in the middle of the winter during a oil change and lube.


When the failure happened in June, naturally, I wasn't anywhere near home. But the repair station a block away from the breakdown was a 4WD and off-road specialty shop. They used fitting-less U-joints to effect the repair.

When I questioned the selection and the owner of the shop showed me several of the vehicles in the yard, all had fitting-less U-joints. Some of these vehicles were road worthy and others were strictly off road. All were considerably more heavy duty than my little Chevy. Chris' explained to me that the Zerk fitting that allowed the U-joint to be greased also allowed dirt and water to infiltrate thereby accelerating the next failure. This could be avoided, or at least minimized by weekly lubrication BUT who's gonna' do that?

A buddy had a similar situation with his Dodge 3500. He does a lot of towing with a construction trailer too. The cheap parts failed in weeks. The better parts lasted longer but still failed in a month or two. Then he replaced with fitting-less and that was 2 years ago. still going.

jmden, ask your driveline guy about this if the work hasn't been done yet.

Pete