Madman, that was very instructive! Thanks for posting that! The book I have states that the trans and pinion angle should be the same (parallel as described in that video) but doesn't explain why. That video makes it perfectly clear!

Having seen that I now have absolute confidence that reversing the wedges will correct my vibration. Based on the measurements I took today, reversing the wedges (since I installed them backward to begin with) will make the pinion and trans output shaft parallel.

I should be able to get that done tomorrow afternoon after work. Possibly including the location dowels I mentioned earlier. At the very least, I'll measure things up and make a sketch so I can turn the alignment dowels another day and toss 'em in when I get a chance.

 

I reversed the wedges and put them in correctly this evening, then measured driveshaft and pinion angles. Trans didn't move, so I didn't bother measuring that tonight.

Results:
Pinion: 2° up
D/S: 5° up
Trans (from last time): 2° up.

So, driveline angles are good: trans and pinion parallel; U-joint operating angle 4°.

Truck still shakes. It's not as bad as it was, it was VERY pronounced especially when decelerating from highhway speeds and approaching 55 mph (on the speedo - speedo is way off with the tall tires). I wouldn't describe it as violent, but it was pretty bad. It had recently gotten noticably worse.

So, now I'm wo dering what's up with the shKe that remains. Like before, it's limited to specific speed range, between 55 and 60. Below and above that 5 mph range and it's smooth as glass. I wonder if my driveshaft is bowed.

Thought?

I'm going to dig around and see if I can find a driveshaft service local (Central NJ). There used to be a place in Hightstown, NJ, not too far from me, Tournquist Garage, that did driveshaft work, but they're long gone. Might be something in Trenton. Anyone know anywhere? I'm thinking have it checked for straightness and balance. It is a steel, one piece shaft.

 

You could road force balance the tires too.

 

That's true. I did mention in an eaier post that I should get the tires' balance checked. They are huge and heavy: 315/70/17 and they're LT tires. General says they weigh 57 lbs each. And when I had them balanced to begin with, I made sure they used stick-on weights only so the clip-on type wouldn't chip the wheel paint. So that could actually solve it.

Meanwhile, I found a place called Mr. Driveshaft fairly close by in Farmingdale and will give them a holler tomorrow and see what they say.

 

With the roadforce balance, ask to watch. If it takes an absurd amount of weight, ask them to spin the tire 180 and check it again.

You can also ask for a mixed weight balance. This will balance the tire using stick on weights and regular weights on the inside of the wheel.

I would also check the driveshaft balance. Ideally anytime you replace ujoints, the shaft should be rebalanced.

 

We'd have to call the Michelin rep from time to time at my old job because the BFG KO2's in the very large variety would always have tons of road force even after flipping the tire, spinning 180, spinning 240 etc etc etc.

I'd tell other customers that bought huge Nitto's or Mud tires that if they shake there is nothing I can do for you. They'd always think that huge 325's or some junk will ride like a cloud on their truck.

If you can get the road force on each tire down to around 25-33 lbs per tire on big tire like that you are doing pretty good.

 

I'll ask a stupid question:

Have you checked the pinion nut? Mine loosened up on me one time is why I ask.

 

Actually, no. That is an excellent question. That never even crossed my mind. Wish my dumb *** thought to check that when I had the driveshaft out last night. Won't have a chance to dig back in to this for a week and a half or so. Working 12's the rest of the week and will ve away the following week.

I did have the yoke in my hand and check the feel of diff bearings, gear lash, etc. The yoke didn't have any looseness or discernable play, so I don't think the pinion nut is loose. It should also be a locking nut from the factory, no? The Benz pinion nuts always were....

 

Back from vacation and have the weekend off. Went and had the big back tire rebalanced yesterday. Each was a full 3 oz. Out of balance. Corrected that and got another huge improvement (obviously).

It still has a little shake, so I will take the driveshaft to be checked out as well. Talking to Mr. Driveshaft, he made sure to stress the importance of checking to make sure the trans yoke isn't bottoming out on the trans tailshaft. So I'll give that a close look again as well. I am pretty sure it isn't, but it doesn't cost anything to check that, and certainly is important.

I'm pretty confident I can get this trucknriding smooth as glass with just a little more effort.