I currently own a 2000 F350 Lariat 7.3 4x4 and a 2001 Excursion Limited V10 4x4.

The Excursion has a vibration that starts around 60 mph. I've been reading this and other forums trying to collect all the information and ideas I can find.

What I've done so far...

• Replaced all 4 brakes (rotors and pads)
• Replaced wheels and tires (I bought new ones for my f350 and put the ones that came off the f350 on the excursion, so I know they were balanced and smooth)
• Replaced the front axle (I put a dana 60 on my f350, so I put the front axle that came off the f350 on the excursion... again, I knew it was in good shape with good ball joints, tie rods, etc.)
• Had the front end aligned
• Finally, today, I replaced the ujoint on the rear driveshaft at the pinion (I discovered the old one was broken).

Through all these changes, the vibration has changed by degree but never gone away completely.

Today, I had a bit of a revelation, and would like any input.

It has come to my attention that some excursions were given a double cardan rear driveshaft, mine included, and some had what I would call a standard driveshaft (one ujoint on each end). From what I know, with a standard driveshaft, the pinion should be angled parallel to the transfer case output shaft. However, on a double cardan driveshaft, the pinion should be angled "in-line" with the driveshaft. I measured mine with a digital level and the pinion is angled parallel to the transfer case output shaft.

My only two possible conclusions are 1) all the rear axles that went into the excursions were set up the same way, so the excursions that got a double cardan rear driveshaft are "wrong" or 2) at some point in my truck's history the driveshaft was changed but the pinion was never corrected. Can someone with an excursion that has a double cardan driveshaft tell me how their pinion is angled?

So finally, my question is, has anyone tried re-angling their pinion with wedges or by cutting and re-welding the perches to get rid of vibration? Does anyone think I'm on the right track?

 

Your answer will be here soon.

 

You say you have a Double Cardan joint on your REAR axle?

If so, that is not what the vehicle came with. All Excursions came with standard configuration rear driveshafts. Small wonder that the Rearmost u-joint would be bad given the angles you say the shaft vs. pinion has.

Maybe someone switched it from one out of a Super Duty (A very few had double cardan driveshafts), the Ex was lifted at some point and it was put in to solve problems, or you have a Gear Vendors unit and the driveshaft was changed out.

I think it was probably one switched out from a Super Duty and the person did not understand the difference the driveshafts can make.

In any case, you are on the right track as far as the pinion angle is concerned. That is IF you actually have a double cardan joint on your rear driveshaft.

Probably cheapest and easiest thing would be to get a driveshaft from the boneyard and put in new u joints.

A proper angle would be pretty steep to just shim the rear axle to meet. It may require repositioning and welding the axle perches. I don't know on your vehicle what would be needed.

 

I doubt the vibration is caused by the drive shaft if it recently began UNLESS its a u-joint. Does the rear end make any noise? I had a similar problem, ended up replacing all the bearings in my rear end....800.00 at ford.

 

Here is my source in all my research for saying that some excursions had a double cardan rear...

https://www.ford-trucks.com/forums/2...ease-post.html

I dont feel that i am alone with that style rear driveshaft, but i suppose i could be mistaken.

Also, it didnt recently begin... it has had this problem since i bought it. Back then when i got it i just thought it was bad tires, but i liked the truck so i bought it anyway..... lessoned learned!

 

I agree with this. My X vibrates at around 75. Its very smooth until about 65 and is at its worst at 75. It sees very little freeway driving so we hardly notice it.

Last time I was on the freeway was a toll road with long straights, no traffic, and a 75mph speed limit. I notice the rear end making some noise unfortunately. It was a bit grumbly and the grumbling got louder when I let off the gas and let it decelerate. From my experience, this is bearings or gears wearing out.

I've had my tires balanced and rotated a few times and that didn't help. I know I have a single drive shaft and the joints are in good shape, so my conclusion is unfortunately a rear-end problem. Don't have the money to get it fixed right now so we'll stay off freeways.

 

Rear ends wear out but rarely cause vibrations unless the pinion is causing the yoke and driveshaft rear to run out of true.

 

Also FYI the guy that did my rear end at ford is a close friend. He only works part part time to get away from nagging grandchildren.. In 40yrs it's all he did was work on differentials. He's never seen the gears in an ex fail. It's always the bearings and 9 times out of 10 it starts with a pinion seal replacement and a moron taking an impact gun to the pinion instead of replacing the crush collar and torqueing it properly. My rear end was the same deal. But it was rumbling, humming and slight vibration. Bearings were shot. 800 parts labor and tax

 

Well, if that's what it ends up being, I can get a rebuild kit for under $200 and do the work myself. I have a dial torque wrench for setting the bearing preload, and I have a press for pressing the bearings on and off, and I get rent a bearing puller for the bearings in the housing, etc. I've rebuilt and set up several axles in the past.... they don't scare me.

I was mainly look for input on why I have a double cardan rear driveshaft while it appears the pinion angle was set for a standard driveshaft. Has anybody else ran into this issue causing dridrive line vibration?

 

Using an impact by itself is disastrous, what they need is a little drag on the pinion to get it snug again. No torque wrenches needed and not going to argue this point.............built hundreds of them.

 

79,
you have the drive shaft info in reverse. A double cardan drive shaft will allow you to run more extreme angle. You would want the pinion more in line with the drive shaft on a typical u-joint drive shaft (Why the rear axle is often times angle shimmed). A double cardan...although not necessary allows you to have the pinion to be more in parallel with the t-case. Double cardan drive shafts are often found on the t-case side of a front drive shaft...because the drive shaft is shorter typically on the front axle so that automatically will increase the angle between t-case and pinion. It is why so many reverse rotation axles are used up front (pinion is on top as opposed to the bottom) to help decrease the angle because of the short distance between t-case and axle pinion.

first question I have...is your vehicle stock suspension. Meaning does it have a lift or not. Did it ever have a lift? That would explain why someone possibly put a double carden on the rear if the angle was increased via lift kit.

#2...are you 100 percent sure the tires you swapped are superb in condition? The bad part is you swapped them from another vehicle and even though they may look good, and possibly were good on the other vehicle, they may be just distorted enough to feel them in the Excursion and not the f-350.

#3...dont laugh at this one..but are your u-bolts good and tight? It doesn't take much distortion from something to give a vibration.

#4 did you change the u-joints on both ends of the rear drive shaft.

#5 the sterling rear end has a rep for ring gear bolts coming loose...although I question this as the problem in your case but you could look into that sort of easily

Good luck on this but in a lot of similar scenarios I would say even though you think the tires are tip top shape..I would not rule them out. Have seen many instances where the tires were nearly new but for one reason or another give off a terrible vibration.

 

Standard shaft:


Double Cardan shaft:

 

If you have a double cardan on your rear drive shaft then my guess is that was put on there by a PO. I have never seen one off the ford line with that shaft. That being said if your U joints are good I do not think a pinion angle issue will cause the vibration you describe. I have read about Pinion angles until my eyes bleed from countless issues I have had with my X. Driveshafts usually cause vibrations in transition not at operating HWY speed, unless they are unbalanced. If the cause is your angle you will feel this on take off or let off. When the driveshaft is flexing up or down.

An unbalanced shaft would cause a wobble all the time but you may not feel it until the speed reaches a certain point the the truck loses its ability to dampen the vibrations.

Give this a read. Driveline 101

Here is one section of particular interest
Fixing Driveline Problems:

Most likely, if you've read this far (or even searched for this page) you may have a problem with driveline vibration or noise. The first step is to characterize the vibration, figure out when it happens, when it gets better and worse, etc.

• Vibrations at relatively low speed (under ~30 MPH) are often due to mechanical issues such as:
  • Phasing
  • Alignment
  • Straightness, either due to a new shaft not being built straight or a used shaft being bent.
    • You would need a dial indicator to measure such radial runout and that would probably best be done at a drive line shop, because after straightening, the shaft will likely need to be balanced as well.
    • Could also be due to a u-joint not being installed properly or a drive shaft flange not fitting properly causing the shaft to not line up with the output shaft or pinion gear.
    • And realize that drive shafts are typically straightened by use of heat and cold. The drive line shop will use a torch to heat one side of the shaft, expanding the steel on that side, while cooling the opposite side with a wet rag to shrink the steel there to pull a shaft back into straightness. That said, any application of sufficiently high heat can case shaft to lose straightness.
• Vibrations at relatively high speeds are often due to balance problems.
  • These vibrations may come and go as speed increases as you move in and out of resonant frequencies of the drive shaft.
• Vibrations that get worse when transitioning from acceleration to coasting to deceleration, like when you back off the gas over the top of a hill and before you go into full on engine braking, may be due to loose or worn parts, like loose flange bolts, worn or over-extended slip yoke, etc.
• Vibrations that get worse say going uphill or accelerating at speed than when going the same speed on the flat or downhill, or vice versa, might be due to a slight alignment issue.
  • If worse uphill/accelerating, the lower u-joint angle may be moving too high as the axle and pinion tip up under load, if so, tip the static pinion angle down a little lower than it is now.
  • If worse downhill/decelerating, the lower u-joint angle may be moving too low as the axle and pinion tip down from the lessened load, if so, tip the static pinion angle up a little higher than it is now.
• Vibrations at very high speeds may be due to approaching the drive shaft critical speed, which is essentially the resonant point where the shaft begins to whip and vibrate violently.
  • In this case, only a new driveshaft design will help, chainging material, tubing diameter or wall thickness, etc.
  • These sorts of RPM limits are usually up in the 8000-10,000 RPM range, so typically only seen in race vehicles.

 

I think you will want to download this for future u-joint reference too.



http://spicerparts.com/sites/default...350-1-dssp.pdf

 

Good article Sammie! Its encouraging that the article talks about yolks and ujoints more than differential internals. I'm definitely going to revisit my joints and see what I can find.