Got the re-tubed drive shaft installed. With the longer drive shaft, I still have about 1.25" travel up, which is in line with everything I've read. They even painted it black to match my Ex.

I guess here's where the plot thickens....

Is the vibration still there? Yes. Is it as bad? Not even close. The ranges have changed also:

50 - 56 has a mild mechanical vibration.

66 - 71 has a VERY mild mechanical but NOT audible vibration.

Up to 85, no vibration. Dripping the Ex off at the tire shop tomorrow morning to check the radial runout of the tires. The back ones (and maybe front) are out of round. I've had a seat bouncing and rattling (you can hear it in the Excursion Psychosis thread) and when it was on the rack at Redline, the PS rear looked like someone was dribbling a basketball really quick. I'm hoping that's the remaining vibration.

 

Still testing it.

The vibration in the 50 range is more noticeable when I take my foot off the gas - it's still completely mechanical. I don't notice any difference in the vibration in the 65 - 70 mph, foot on or off, it's just there, and very mild.

Under ordinary circumstances, I'd be screaming pinion bearing... God I hope not...

 

I should add that cruising at 75, then taking my foot off the gas, the vibration is barely noticeable as the speed drops down below 40.

 

Mine was 57" ++

Best thing to do is crawl under and measure flange to flange and see what you get for length.

 

Tires checked out by two shops today - all the tires are fine.

The ONLY things that haven't been touched are the u-joints in the double cardan, the transfer case and the transmission.

So to add to the symptoms: I remembered a trick someone once told me when diagnosing a drive line vibration. Only problem is, I can't remember what it means. When you have a vibration, remove your foot from the pedal and put the trans in neutral to see if the vibration is still there. Did that, and the vibration is still there.

Can one of you wise Ex fanatics refresh my memory as to what that might mean? If anything?

 

YOU HAVE A DOUBLE CARDAN?

From the photos you posted showing lift blocks I did not notice blocks being tapered.

Those type of driveshafts need the pinion flange to be almost perpendicular to the driveshaft, unlike the driveshafts that only have 2 ujoints. Most DC driveshafts need a tapered block to achieve this.

Check your flange and driveshaft angles....and set up properly if not already correct.

 

Yes, I have a double cardan. Which I rebuilt today, which is a motherf$!@!&g PITA!!! Rather do a wheel bearing or ball joints any day.

Crawled up under the truck today with my son's protractor to try and estimate the pinion angle. If my eyesight is to be trusted using a protractor, it looks like the driveshaft is 2 to 3 degreed away from being perpendicular.

As it is now, the vibration symptoms are as follows:

Mechanical vibration from 48 - 58, felt in steering wheel and floorboard.

Mechanical and audible vibration from 64 - 76, comes back about 82. Felt in steering wheel, floorboard an seats.

I'm about to give up. Can the pinion angle cause those types of symptoms?

 

2 degrees out is borderline, I would shim at 3 degrees out.

But if I were you I would check to make sure hubs are unlocked. The way you describe the vibrations it almost sounds like 1 or more hubs are engaged.

Or transfer case is stuck in 4X4.

 

Hubs are not locked. Front drive shaft spins freely, as do front axle.

Could the lack of sway bar endlink bushings cause some of this? Found out last night mine are all but gone.

 

My girlfriend typed my previous response since we're on the road. She's driving now, and it's my turn.

I wouldn't take my angular measurement as gospel since I did it with a plastic protractor and eyeballed the centerline of the drive shaft. It might well be 4 or 5 degrees - or my eyeballing might be accurate. The fact remains the vibration was not there before the truetrac install.

I think part of the vibration in the steering wheel is an indirect result (or direct) of the diff rebuild. Last night I loosened the nuts on the sway bar end links there appears to be no usable bushing material left, as I could twist the bottom of the end link and the top of the link would rotate enough to hit the frame.

I took it for a test drive. MUCH less vibrations in the steering, not completely gone, but it was better. Got back home, tightened everything up, and the vibrations were back.

This affected only the 48 - 58 mph vibrations. I didn't take it any higher than 55 with the sway bar disconnected.

There's a sweet spot between 60 and 65 where the truck is smooth as glass.

The reason I think it's from the Trutrac install is this; they used a frame lift to raise the truck. With the front axle left unsupported, the rubber bushings in the sway bar end links that were dry rotted, pretty much disintgrated. Now there's just bits and pieces of bushing material.

At least that's my latest theory. Might be completely wrong...