Can someone clarify this?

I have been reading the posts about vibrations and drive shaft angles.
It appears for many of the posts that the vibrations get worse as you
go faster.
But a few posts suggest that it gets worse when you take your foot
off the gas and coast at high speed and that the vibrations disappear
when accelerating.

So which is it? If you have a drive shaft angle problem, do the vibrations
disappear when accelarating at high speeds or are they always there?

I also read a few posts about a black rubber vibration damper.
Is this something to check before you suspect a bad drive shaft angle?
How?

I currently have the vibration problem only when coasting (foot off the gas)
and the noise from the vibration appears to get louder as I slow down.
It also feels like there is a drag on the truck when I try to coast.
The vibration is still present when I put the tranny into nuetral and coast.

There is also a small clunk noise when the brakes are initially applied. It sounds like something in the chassis shifts slightly. Could this be an indication of a loose motor/tranny mount?

Any help would be greatly appreciated.

Sincerely,
Grcutter

 

I had the same problem with my 2000 x 4x4. It ended up being the front drive shafts and bearings. Had one grove the spindle and had to replace both bearings on each side. Hope this helps.

 

Do you know how they identified this problem?

What did it cost to get it fixed?

Grcutter

 

It wasn't a quick and inexpensive fix. I had a local dealership say it was the torc converter in the trany and quoted me a price to replace. I did not do the work until I found a shade tree mechanic. I told him the problem and he also agreed it was the torc converter. After spending around $1000 with the vibration still there, they tore down the front of the truck to discover that the bearings were bad and the 1 spindle. Ended up costing me around $2200 on something that should have cost less than $1000. Lesson learned....
<O</O
<OI could tell looking back on everything that it wasn't the torc converter, A) it still did it when you would put it in neutral and coast. B) it wasn't that bad when you would turn to go around a corner or steer back and forth going down the road. Especially when you took the pressure off the side that was vibrating.

Hope this all helps....
</O>

 

The problem gets worse as you go faster and is worse when you just let off of the gas. I have had the exact problem. The angle is off between the Rear End and the Drive Shaft. Mine angle bad from the factory. I have a 2003 Excursion. After weeks bothering my dealer they finally figured out the problem and inserted 6mm edge shims and it took care of the problem all the way up to 78 MPH. Now I'm trying to get the dealer to insert a taller shim to take care of the problem above 78 MPH but they are washing their hands clean. I did a ton of reasearch on this so let me know if you want more info.

Brian

 

http://www.vibratesoftware.com/html_...aft_Angles.htm

Read this information about three times and then fix your rear drive shaft angles. Make sure to use steel shims - not the aluminum ones 4Wheel Farts will try to sell you. My front a rear u-joint operating angles are matched a 6.5 degrees up and my driveshaft angle is 10 degrees up. This process is a pain in the butt, but you have to do it right if you want the truck to run smooth and your u-joints to last.

Once you get the angles right, then get your drive shaft lengthened if necessary and then balanced. The one piece Excursion shaft's are generally too short for even small lifts and require addtional length to maintain proper spline contact. Take the shaft out and measure flange to flange, top and bottom to determine proper length. My Shaft is lengthened 1.125 inches with only a two inch lift in the rear and balanced to run up to 103MPH. That was as good as it would get and I'll never go that fast any how so it doesn't matter that it wouldn't balance to the 120 MPH the machine will do that it was balanced on.

Also - make sure that the driveshaft shop actually can balance a shaft. Most do not have the equipment to balance drive shafts, allthough most will tell you that they do. They lie. They will talk about run out - which is straightness - and other things, but most simply do not have the equipment or personnel to balance shafts.

If you don't want to dick with this just get a double carden shaft for your truck, shim the rear diff to point straight at the driveshaft and be done with it. Downside - double cardens are expensive, wear fast and eat u-joints.

Good luck.

 

Spartan,
Thanks for the link. I had also found that by searching the forum archives.

Do you have an explanation for why the drive shaft angle would change over time? i.e. If it is off, what may have caused it to be off? Has something moved or shifted?

I'm not convinced that I have a drive shaft angle problem. The noise/hum that I hear grows louder as I slow down and is only present when coasting. The drive shaft angle problem appears to be the opposite, the noise grows louder as you speed up.

I'm focussing on the U joints and the front axle.

Sincerely,
Grcutter

 

My noise got louder slowing down also. It didn't almost completely disappear until I had my angles checked and we inserted a 4mm spacer to turn the front of my rear end up. Now I inly have a vibration at 78mph and louder.

Brian

 

When slowing there is torque created from the engine breaking and can increase - or decrease - however you want to look at it - the angle at the differential, which in turn increases the problem / noise vibration. They call it body boom in th lift business - I call it vibrational resonance. When you apply power and the torque is reduced the differential returns to near it's proper angle and the noise goes away.

It's really simple - take your shaft off and measure the angles. It take five minutes and then you will know whether that is the problem or to look elsewhere. While you are under the truck you can check your u-joints.

 

How do you check U-Joints?

Brian

 

Grab the driveshaft and shake the snot out out of it. If nothing moves except you and you get really tired and frustrated you are good to go. If there is any slack or movement in the u-joints - replace or have them replaced. Good luck.

 

Also - I forgot to mention one thing. In my experience trucks lifted over two inches never run right again. I guess that's why they don't sell them that way. I've done everything under the sun to get rid of high speed vibration and it's still there over 77 MPH. So I just don't go over 77. No problem really, but it drives me nuts that I can't fix it. Anybody know how - please post the answer on my post on the SD forum.

 

Mine has never been lifted. Everything on it is stock. That is why I'm so frustrated with the body boom at 78 and higher. For will not work on any vibration that occurs over 75 MPH.

Brian

 

Well - on one hand I'm glad to know that I'm not the only person around suffering from this problem. On the other hand - it's BS - Ford should design a truck to run smooth stock or lifted and they evidently can't do it. I'm seriously thinking about a GMC Yukon XL. It won't carry or tow as much, but I will be more comfortable and the BS factor will be gone.

 

I feel the same way. If I could afford it I would get rid of this truck and get a Yukon XL tomorrow. I'm tired of these problems.

Brian