Drive line vibrations

[bkahler]

Wow

Talk about a lot of great advice! Beginner, thanks for the great detailed description on what to look for. Now all I need is some dry ground and time to crawl around under the motorhome. All of this is going to have to wait until after Christmas and New Years.

I'll post an update once I have a chance to look things over.

Thanks again

Brad

[bkahler]

THE DRIVE SHAFT MUST BE IN A STRAIGHT LINE IN ONE DIMENTION, PERIOD, NO EXCEPTIONS.
Since the engine and the differential are at different angles then the drive shaft must be straight as if you were looking straight down from above or looking up at it.
I checked mine with a string. I rotated the drive shaft so that a u joint bearing cap face (flat) was straight down (parallel with the ground).
I tied a string at the differential on the pinion shaft.
I tied the other end to the transmission yoke.
I tied the string tight.
I centered the string on the u joint bearing cap at the differential and on the bearing cap at the transmission yoke.
The center u joint bearing cap was about ¾ of an inch out of straight.

If I understand this correctly you're verifying that the driveshaft is in straight alignment from side to side. In other words when looking up at it from below you should see a straight line.

I moved the tail shaft of the transmission to the right (passenger side) as far as I could to remove part of the problem….

Makes sense based on the description above.

….and shimmed the center bearing to remove the rest of the out of alignment condition. To do this safetly I had to cut a 2 inch wide ¼ inch flat bar longer than the center bearing was wide and drill two holes in it. This I placed on the top of the center bearing. This was to hold the center bearing and the rubber shock mount for the bearing in the u shaped bracket the center bearing assembly lived in.
Then I started shimming with washers until all misalignment was gone.

This step makes it sound like you're moving the center bearing up and down, not side to side as I would have expected. Did I miss something? I can understand the need for the 2" plate if you've moving the bearing up and down. If you were moving it side to side I wouldn't think you would need a metal plate. So I'm confused on this step

My first trial run of flooring the gas pedal was nothing short of nirvana.
Smooth as silk.
And it only took me two years to figure it out.

I certainly hope I don't take two years to get this far! Congradulations on figuring out what needed to be done and getting it done.

As a precaution I replaced the transmission tail shaft bushing and transmission rear oil seal.

Good idea. I'll look at mine closely once I get time to crawler under the motorhome.
Thanks!

[TBSarfari28]

Brad,
Before you get under the rig, take a look at the videos on the web page I posted. It is not to diffcult to check driveline algnment using a bubble protractor to determine if the u-joint working angles are within specs. They must be within specs or they will not cancel each other. In your question above, checking to see if the driveline is straight from side to side, In some longer wheel base vehicles the driveline can be a compound arrangement. In a compound driveline arrangement the transmission output shaft and the diff. input/pinnion shaft are parallel as seen from a top view and side view, but not inline to each other top and side views. The single plane arrangement the top view is straight from the trans output into the diff. input. The side view has the the two shafts parallel but not straight inline to each other.(see the videos) If the rear axle is not parallel to the front axle your vibration could be caused by this condition. Usually when the front and rear axles are not parallel your vehicle would dog-track, do down the road side-ways. This condition would also cause the front tires to wear the inside edge of one tire and the outside edge of the other tire. If you don't have this tire wear, most likely your axles are parallel. Check all the components discussed above, then check driveline algnment to determine if u-joint angles are within specs.

[Beginner]

Yea, it took two years, but only 6 months after I got my Airstrream because before the Airstream I was not towing anything.
The two inch wide flat bar was to hold the center bearing assembly together. (The center bearing is set in rubber [shock mount] and that bearing/rubber assembly slips into its bracket from the top. When you bolt the bearing assy to the body, the body keeeps the bearing/rubber assembly in the bracket. The flat bar was to keep the bearing/rubber in place while I was jacking the bearing up and down and left and right with the washers.) I installed washers under both sides to drop the center bearing to bring it into alignment as close as possible up and down. Then installed washers under the drivers side only to swing the center bearing to the passenger side to finish the adjustments.
I had to install longer center bearing mounting bolts. I replaced the shorter bolts with Grade 9 hardware of the same size (diameter). They were either 3/8 or 5/16 fine thread.
In my opinion though the problem was caused by the center bearing being too far to the left (drivers side).
I was afraid that the vibration had wallered out the rear bushing. You have to remove the rear oil seal to get to the rear bushing to collapse/remove it
If I can help further, please ask.
Beginner