I have the dreaded 45mph rear end bounce, I have new bilstien shock's,two set's of wheel's and tire's both road force balanced, tpms reset so I can run lower tire pressure without getting A light on the dash with running lower tire pressure and I still get the bounce. I have had it looked at at the dealer four times and have had all the new flashes. I have read the other post reguarding this issue all the way through and there is acouple of comment's that airbag's may have fixed this issue, but no one has confirmed.

 

Here's a pretty weak response: It depends.

The airbags will help if the bounce is due to the rear end sagging under load. By inflating the airbags, the rear end is raised about 2 inches and the drive shaft is returned to close to an unloaded position. The airbags also take a lot of work away from the springs which again, returns them to a nearly unloaded position.

Some people have attributed driveline vibrations to drive shaft angle. Others have attributed bouncing and hopping to compressed rear springs. Both of these situations can be remedied by airbags.

 

Are you talking about the freeway hop on the expansion joints?

 

Joints, bumps, whatever. Any bump or vibration that would normally be transmitted through the springs are partially mitigated by the air springs. Vibration due to drive shaft/carrier bearing binding or misalignment is also solved by restoring the level to the rear end.

 

If a 250 and a 350 have the same everything except for the additional overload spring and higher block on a 350 how do you describe "level", or "normal" driveline angle?

Maybe I am making the assumption that both configurations - 250's and 350's - are prone to this issue, not just 350's?

 

I never had a chronic hop as some have posted so I'm probably not the guy who should be speaking. My experience was been with pulling heavy trailers and the airbags are indispensable for that. When I mention level, I'm referring to removing the sag in the rear end when a heavy load is put in the back. My trailer pushes the rear end down about 3 inches and the airbags push it back up 2 inches. The drive shaft angle at the U-joint changes when compressed vs. uncompressed so there is a potential for different behavior or sounds when it's traveling through those extremes. I don't think it's fair to say either 250's or 350's are "prone" to the issue since I and most others are exempt.

We've been talking about two different issues, vibration and hop but both are reduced or eliminated by the airbags.

 

The answer is a clear no. I have done the following on my dually with no help -

-2 different sets of tires
-road forced balanced tires
-shimmed carrier bearing twice at different angles
-new bilstein shocks
-installed ride rite air bags
-rebalanced factory drive shaft
-old tsb #0905 done which includes shimming leaf pack stack to change angle
-new heavier duty driveshaft assembly

The new driveshaft cured a shuddering on take-off that I was having, but none of this helped with the harmonic hop that happens at times. Good luck, and let us know if you find any solutions. Cheers,

 

Gotcha. Just "food for thought"

 

Another user reported a new bounce at 45-50 on an 04?!.. (at 128k miles)

maybe something can be learned there..

https://www.ford-trucks.com/forums/1...l#post11783405

 

I had the drive line shudder with my 5th wheel, about 3K of pin weight. It would drop the rear of the truck about 3-4".

I now have an air kit in the truck and with the height equal to unloaded or slightly higher, I still have some shudder.

As to the 45 mph "hop. I occasionally had it before air ride and I still have it occasionally.

Although, pre-post air ride it was barely noticeable.

 

I agree! I also have tried most of these cures (except the old tsb) and nothing has helped.

KC8VO, No it is not limited to 350 or 250, SRW or dually, long bed or short bed, those of us who have had the bounce have not been able to point to any one truck charectorisic that causes the bounce. I have lived with mine for two years next month and have given up throwing money at it trying to fix it. Now when I hit 40, I just punch it and jump past 45 to get out of the bounce cycle.