Dropped the drive shaft off at the shop to have it checked.

This is a result of the endeavors listed in the Excursion Psychosis thread, my pinion bearing was causing a nearly impossible to find noise. Once I got the Excursion back from having the Truetrac and new bearings installed, I had a mechanical vibration from 45 - 55ish and mechanical/audible vibration from 65+ mph. The vibrations were present during acceleration, cruising and deceleration.

While on the lift at the shop that rebuilt the diff, there was a noticeable wobble at the slip yoke while the enine was running, in gear, while trying to track down the vibration. On the ground, there MIGHT have been about 1/32 of an inch play according to the eyecrometer.

On the ground, the distance from the center of the front most u-joint to the rear most u-joint was 53" according to the tape. The driveline guy removed the boot from the drive shaft, laid it out on a workbench and measured 53". He said with that distance, I only had about 1 1/2 to 1 3/4 inches of engagement on the splines on the slip yoke.

He need the drive shaft had the original Ford sticker, with a manufacturing date of sometime in 2000 (I can't remember the date). He then asked if the truck had a lift, which I replied that I believe it has the F350 blocks, and at least one extra leaf on the rear springs. He told me that with a 4" lift, the drive shaft should have been lengthened sone where between 1 1/2 to 2 inches, depending on the distance between the transfer case flange, and the yoke flange while the truck was at rest. The distance is a hair shy of 56 1/8 inches.

Besides the length issue, he said all the u-joints are in great shape and don't need to be changed, and the glide coat on the slip yoke is still in excellent condidtion - the drive shaft only needs to be lengthend, trued and balanced.

Does the above sound reasonable to you guys?

 

Nope, I have 2 Excursions one with OEM suspension and one with a V/C spring setup and F350 blocks. 3 or 4" lift or so.

There is 1/4 inch difference between the transfer case flange and rear end flange distances between the 2 excursions. Both of which are 2000 model yr 4X4s.

If my memory serves the OEM distance flange to flange was 55" and the f350 excursion suspension measured 55.25 flange to flange.

 

Hmmmmm... interesting. Almost identical set up, and the distance on mine is 13/16 longer.

Edit: and my springs are a bit saggy, as well. Though I'm pretty sure there's an extra leaf or two on my rear springs. Might be mistaken...

 

Yup, odd

Maybe your leaf springs had spring mounts set back an inch.

What wheels are on it, OEM?

 

No, Vision Warrior 375's - tires are 315-70/17's I believe.

 

Took some measurements with pics:









The block doesn't appear to be from the an F350 (which I believe is 3.75") - it's a full 4". Not clear in the one photo, but, the spring pack appears to be a little over 3" thick - no idea what stock is.

 

http://www.visionwheel.com/page/2/faq

Read the above faqs: vibrations could be caused by lug centric wheels on a vehicle that was designed for hub centric wheels.

Above is from your wheel manufactures Web site.

 

These have the ring.

 

Well all I can think of now is maybe the differential was not correctly set up or maybe you need to grease the yoke.

Although if the OEM distance between flanges is the 55" as mine is maybe a longer driveshaft would help.

Measuring the angles on flanges to make sure they are correct could be informative.

 

Just as an fyi, I've had all the wheels off this truck a number of times, and never had a mechanical vibration like I do now, so, I doubt it's a wheel issue.

I'm calling the shop first thing this morning to discuss what they think the actual drive shaft length should be.

When the Ex was on the rack at Redline (who did the diff ), the wobble and play in the drive shaft was easily an 1/8" - maybe more - but the rear end was hanging in the air, also. On the ground it was much less, but, still had a little play. My worry right now is, if they lengthen it too much, the slip yoke bottoming out on the drive shaft durine rear end articulation.

Wish I had an inclinometer so I could have checked the drive shaft angle. That way, I could have done the math on the angles and distances, and calculated the slip yoke travel myself so Um not going into the blind...

 

Tracking down vibrations can be frustrating.

A cheap angle level or protractor with a string will get the angles you need. Home depot has those things.

Here is what I would do.

1) because driveshast was extended due to rear axle hanging the grease in yoke may have been pulled out too and just needs grease. Remove DS and remove rubber boot between yoke and DS. Pack yoke with a #1 grease....not #2 as I was told it can be too thick. Reinstall the assembly and see if vibration goes away.

2) while DS is off take some angle measurements.

3) pretty sure that differential specifies non synthetic gear lube. Check that.

4) when I did my DS grease I think I remember that the yoke is splined so u joints line up, but maybe when they did your rear end they miss aligned your yoke. Check it for proper allignment.

Really don't understand how lug centric wheel vibrations can be fixed with a hub centric ring. Lug nuts are still acorn style and as you torque they "pull" on things to try to center wheel to lug nuts. Any type of minor lug stud movement or bending that could have happened when they pulled your axles to install traction device could cause a vibration.

 

This.... I know.... sadly..........


You'd think with three kids in the house I'd have a cheap protractor...


Drive shaft is already out and being worked on. I saw the measurements at the shop - sitting the ground or jack-stands, the DS had less than 2" of spline engagement. The goal being to make sure I've got at least 2x the spline engagement vs. spline diameter.


You are correct. I made sure to tell them to use 80W-90.


This might well have contributed to the problem. I can't say for sure.

 

THIS!

Also, my Ex has a 5.5" lift and I have had no issues with driveshaft length.

 

Man... this whole situation is damned confusing

 

I hope you figure it out as I feel like I am chasing the same thing. Vibrates at 68, gets worst at 72 and better at 76-77. Rebalanced the drive shaft, balanced tires, u joints fine, etc. I am going to switch wheels/tires off my truck and see if that's it. Keep us posted please