Does this mean spring rates or lengths are different?

 

Wow Ben! You really got a response on this post. I'm sure that your head is spinning at this point. Lots of good information from guys with good experience. I've done a lot of this over the years and it gets to a point where you just have to go back to basics with your diagnosis. Your tires are pretty good sized for MII suspension. I'm assuming that you took that into consideration when you chose your springs. You really described 2 different problems at least as I understand what your doing. Vibration being up and down and wobble being from side to side. Vibration is usually controlled, assuming a good spring rate, by your shock absorbers. There you have a lot of choices ranging from 50/50 up/down valving to 80/20. Given that you have checked your wheels and tires a couple times then wobble or side to side movement (and I'm assuming that this is the higher frequency wobble vs wander) is normally felt in the steering wheel. This can be caused by components that are too loose or movement in the steering components (don't forget frame flex). Finally make sure that your rack height is correct. I'm not an expert on MII suspensions but I have worked on other R&P systems where that is critical. Normally on race cars that is associated with bump steer but it is worth checking. There is lots of information about this on the internet, here is one http://www.racecartuner.com/03/203.html

That's my 2 cents. Hope it helps . . . Good Luck!

 

I'd start off by jacking up the rear and putting it on jack-stands. Fire up the truck, put it in gear and run it up to the speed where the vibration/wobble usually occurs. If there is no vibration, you have eliminated about 75% of what has been suggested; engine, trans, driveshaft, axle and rear tires. If the vibration is there, have someone in the truck to run it up to speed and start looking at components, driveshaft, rear wheels and such. After this checking the front-end should be easy.

 

Hey Ray,
The springs up front were selected based on the 351W V8 engine.
The wheels are pretty big for this application - I was having a problem with the front left hitting on the rebound off of bumps or dips. It also happened going downhill & turning right - the weight of the truck went to the front left corner & the fender & tire would rub. The tires were within an inch or two of the fender - very tight.

I adjusted the front coilovers up as far as they would go & still was hitting some so I stuck a "Spring Spacer" on that side - effectively pushing the springs up a bit on that corner. It's not ideal - I think the real solution is to get new smaller tires/wheels or slightly heavier duty springs (I guess).
I wonder if I should have done it to both sides up front?

It's not rubbing any longer but I know it's a bandaid & I will circle back.
What do you think? I don't have any experience with spring spacers.
(I'm trying to stay away from the "Hey Ben - Your whole front end is welded in there wrong... I had some experienced help).



Ben in Austin

 

Hey Pete,
I am trying to decypher it all & come up with a logical plan other than
just throwing money at it. Mechwagon - that's a good idea - to try to eliminate the back from the equation.

Pete - I'm going to take it out here in a minute & try to get a better description of what's going on - Vibration (up/down) vs. wobble (Side to side). I have to share that it is very frustrating/annoying if that helps any - I've got something wrong here. I am not super familiar with bump steer - I don't feel anything hitting when I turn. It tracks straight - I'm not getting any wandering around. I'll repost vibration thoughts after one more drive (Not at Arrowheadfred speeds).

Ben in Austin

 

Are you using a stabilizer bar up frt? They will stop body roll.

 

Hey Guys,
After just driving it again - I went to the store & took it up on the highway for a bit. I'm going with excessive wheel hopping as one problem - just seems like the tires are hopping up & down as you go along as opposed to staying on the surface.

I can't distinguish between whether the front & the back are doing it or just the front. I'm going to put it up on blocks & see what's shaking the most if possible.

Ben in Austin

(Hey Yamagrant - Our Mustang II "Kit" came from No Limit & it has a front stabilizer bar installed & I added one in the back as well that came with the Explorer rear end).

 

Once you get it up on blocks, watch the outside circumference of each tire very closely from the side as you spin it. It certainly sounds like you have a tire that is out-of-round. Do you have a spare? If so, use it to single out which tire is causing the problem. Like I said before, even brand-new tires can break down like this.

 

I would be very careful using jackstands and taking it up to any speed over 5 mph. Make sure that you do it outside and that nobody or nothing is in front of you. If you can get access to a dyno then that would help you see front or rear at speed. Certainly safer too. In the long run it may be well worth the money.

I would be more suspect of the front suspension except that you say that you are unable to tell which end is vibrating. Driveline phasing and pinion angles are usually mild but annoying vibrations that you feel in the seat. Front end though comes through the steering wheel and can be severe. On 4x4 trucks with big tires the use of a steering dampener is standard equipment these days (sideways 50/50 shock connected to the steering tie rod). Without it the description earlier of "death wobble" is quite accurate. That happens on bumps, train track crossings at 45 degrees to the traffic flow are the worst. The entire truck comes loose at any speed over 40 mph. Videos taken from the side of the road are quite impressive. You might want to try that if you have an iPhone. You might see something.

I didn't notice if you said or not but did they use an on-car balancer when they balanced your tires/wheels? Most large Jeep dealers and some Goodyear tire stores use those.

Let us know what you find. Diagnosing vibrations is second only to squeaks and leaks when it comes to frustration level. Hang in there. You will find it if you are methodical.

 

I was just watching and reading all of the posts.

Had a similar thing happen on my wife's 01 Navigator. I had two front tires replaced with some Good Years. Soon after, the front developed a shimmy/vibration whenever we drove it at freeway speeds. I racked my brain as to what it could be. I had it aligned twice with both times it being perfectly within specs. I then thought that maybe it was a bad hub. Took into a shop. To my surprise, they found that the right front tire had a damaged belt on the inside of the tire that turned into a small lump and wasn't visible when looking at the vehicle. I had the tire replaced under warranty and the wobble went away.

 

Here is a brief description of bump steer http://en.wikipedia.org/wiki/Bump_steer

 

Pretty much identical to what happened with our Expedition as I described earlier. It drove me nuts. I had it aligned and balanced at least twice. Every single time, the vibration came right back. The vehicle was brand-new. Finally, I talked to a service manager at the dealership and he found the problem. Broken belts on brand new tires.

 

Hey Doc & Panelman,
It just has to be something with the tires though they are brand new.
I've balanced & aligned the tires at two different places - frustrating if that's what it turns out to be. I am leary of putting the truck up on stands & going any speed - just looks dangerous.

I'll keep you posted - might have to wait till the weekend when my son Zack comes home. It works better with two eyes & ears trying to diagnose this vibration thing. It is getting frustrating - so hard to nail it down but we'll get it - Thanks to everyone for your help & suggestions.

I may hit up Discount tire Saturday for their more involved "tire test" that Sam mentioned earlier. As far as I know all balancing has been done off the truck.

Ben in Austin

 

Yes, your on-car balancer will show shifted belts.

 

Bueller? Bueller? Bueller?

It's not a Ferrari, but will do the same damage.