tsb for launch shudder; Understanding driveshaft angles

[RedSled]

This is in reference to TSB 03-003-04 Launch shudder (long)

I bought an 05 that had launch shudder which I was able to fix by lowering the center bearing about 1/4 - 1/2 an inch. I went on a long trip last week towing the 5th wheel and had a bad shudder from a complete stop. I was loaded down pretty heavy, as the bump stops where about 4 or 5 inches from the axle. (I just ordered a set of air bags)



I can't imagine that the driveline is that sensitive to weight. On my 97 I could put 4k lbs of gravel in the back and never felt this.



Obviously there are issues with the 3rd gen's driveline engineering. do a search on vibration and/or u-joints and look at the number of threads.



Last night I decided to take the measurements as shown in the TSB. I bought an angle finder from Lowes and used that to get my measurements. (I removed the snap rings and placed an a socket on the U-joint cap)



Here is what I found

transmission yolk output angle 4. 5 deg.

front propeller shaft angle 4 deg.

rear propeller shaft angle 5 deg.

pinion flange input angle 2 deg.



so based on the calculations shown in the TSB



transmission to front shaft angle is . 5 degrees

front shaft to rear shaft is 1 degree

rear shaft to pinion flange is 3 degrees



ALL MEASUREMENTS WERE UNLOADED



question 1) what happens to these measurements when loaded? which measurement changes and how?



question 2) how do I change the rear shaft to pinon flange without changing the other measurements. I think if I lower the carrier bearing any more the transmission to front shaft angle will get larger. (my understanding is it is best to have this angle as close to zero as possible).



question 2a) when I was searching yesterday I saw where someone used shims for the rear springs or axles. what angle do the shims change?



question 3) will the air bags if inflated when the bed is loaded bring me back to the same angles as if I am unloaded



question 3) why in the world am I having to deal with this?



This is without the 5th wheel attached as it was pouring down rain, and I was in the garage.

 

[Mathew Clausen]

Check u-joints

Sounds to me like you could have a bad u-joint. The reason you feel it with the trailer may not be from a change in angle, but just from the increase in load. You might try driving at highway speed and then get out and feel each yoke ear - if one is noticeably warmer then there you go. Otherwise - remove driveline ...



Mathew

 

[RedSled]

I thought about that, It is hard to check them without removing them. I cant imagine they would be bad with only 1000 miles.



I am not sure I understand this, but I think when adding a load the pinion angle goes from negative (pointing down) to positive(pointing up) ,and that creates the vibe.



Not sure about that though. If that is the case I would have to create more pinion angle with no weight so it wouldnt go positive when loaded.

 

[RedSled]

I just thought of this question

what happens to the pinion angle when you accelerate? does it move up or down?



Which every way it moves, it would probably move more under a heavy load.



I guess this is what is referred to as axle wrap???

 

[Rodboy]

Is your truck an automatic? My fathers 03 would do that when he loaded it real heavy. It would shudder when he took off or tried to accelerate. Once he craterd the transmission and had it rebuilt by DTT it hasn't shuddered since. Everyone knows the dodge stock autos are crap when you load them heavy. Just a thought.

 

[RedSled]

I dont think its the transmission. It is a similar shudder to the one I felt when it was unloaded. I fixed the unloaded shudder by lowering the carrier bearing.



I dont think I can lower it any more, or I will change the angle of the transmission yolk to front shaft.

 

[JHardwick]

This is in reference to TSB 03-003-04 Launch shudder (long)

I bought an 05 that had launch shudder which I was able to fix by lowering the center bearing about 1/4 - 1/2 an inch. I went on a long trip last week towing the 5th wheel and had a bad shudder from a complete stop. I was loaded down pretty heavy, as the bump stops where about 4 or 5 inches from the axle. (I just ordered a set of air bags)

What you did was mask a bad ujoint by taking angle out of it with spacers. A straight, or nearly straight ujoint doesn't move much. But then with the load, you moved the shaft in the opposite direction which had more angle on it because of the spacer. Now the ujoint is trying to work again, but it's tight/seized and can't.



After experiencing this shudder 3 times, having the dealer replace ujoints twice and replacing them once myself, I'm convinced the angles are fine with no spacers. It's all in the tight/seized joints trying to make the shaft assembly woller in the rubber carrier/damper. If you stretch a string from the pinion yoke to the slip joint yoke, the centerline of the carrier should sit above that string with the truck empty ... ... ... ... below the string heavily loaded ... ... ... and, pretty straight with a medium load. If you have it straight empty (by adding spacers), and then load heavy, you have introduced some serious angles that a dry joint can't handle.



Every time the joints have been replaced, the shudder goes away until they try to seize again. I now have the geasable 351's and don't expect to ever have the shudder again.

 

[JasonCzerak]

What you did was mask a bad ujoint by taking angle out of it with spacers. A straight, or nearly straight ujoint doesn't move much. But then with the load, you moved the shaft in the opposite direction which had more angle on it because of the spacer. Now the ujoint is trying to work again, but it's tight/seized and can't.



After experiencing this shudder 3 times, having the dealer replace ujoints twice and replacing them once myself, I'm convinced the angles are fine with no spacers. It's all in the tight/seized joints trying to make the shaft assembly woller in the rubber carrier/damper. If you stretch a string from the pinion yoke to the slip joint yoke, the centerline of the carrier should sit above that string with the truck empty ... ... ... ... below the string heavily loaded ... ... ... and, pretty straight with a medium load. If you have it straight empty by adding spacers, and then load heavy, you have introduced some serious angles that a dry joint can't handle.



Every time the joints have been replaced, the shudder goes away until they try to seize again. I now have the geasable 351's and don't expect to ever have the shudder again.

I had a "minnor" shutter "fixed". . they made it worse... I put a small load, say about 1500 pounds, enought to makie the rear sit down a few inches. NO SHUTTER AT ALL.



I have yet to have them reverse things.

 

[RedSled]

Someone has to understand this!!

come on guys! someone has to understand how these angles work. Maybe my first post was confusing, or maybe I am calculating this wrong.



I attached a drawing showing my angles.



What I am questioning is the pinion angle.



Based on the picture is the angle 3 degrees or 7 degrees?



What happens to this angle when weight is added? Does the pinion point up more or down more?



Thanks again. I am going to figure this shudder thing out!

 

[J&LRam]

spring wrap under hard acceleration and 2100 lbs of 5er pin weight makes mine shudder bad in 1st and 2nd. I added Timbrens that doesnt let the rear sag so much and doesn't shudder as bad. There is no shudder when empty... ..... JIM

 

[JHardwick]

come on guys! someone has to understand how these angles work. Maybe my first post was confusing, or maybe I am calculating this wrong.



I attached a drawing showing my angles.



What I am questioning is the pinion angle.



Based on the picture is the angle 3 degrees or 7 degrees?



What happens to this angle when weight is added? Does the pinion point up more or down more?



Thanks again. I am going to figure this shudder thing out!

Your making this more difficult than it really is. Have you greased your u-joints lately?



BTW, if your driveshaft is coming down to the pinion at 5*, and your pinion is nosing up at 2*, the u-joint is working at 3*.



AND ... if you load 'er down, the pinion angle stays the same, BUT, the pinion u-joint will work at less of an angle.

 

[tkerrigan]

The transmission-transfer case and the rear end angles should be as much as possible, the same. IE if engine is 4°, then the rear end should also be 4°. If possible. Also, all items should be lined up side to side. The centerline of the engine should aim directly at the centerline of the rear end pinion. If you were to stretch a string from the directly under the center of the harmonic balancer to directly under the center of the rear end pinion, the centerline of all u-joints should be directly over the string, many times the center u-joint is to one side or the other.