Shudder when starting out

[TCDiesel]

C-MEN, I agree with you on this one ,I rebuilt my own 47re with ATS stage IV ,I did like NOT the hanger bearing design,the coupling is way to close to the hanger, the u-joint is also very close to it. When under stress I think it is causing it to vibrate,It will do it in forward and reverse. After traveling highway speeds for a period of time it is more prone to vibrate. Only at take off once speed is 7 MPH+ it stops very annoying. A longer yoke may solve the problem.

 

[JDerbedrossian]

i just recently put 4 inch superlift kit on truck. it has 2 inch blocks for rear, first thing i noticed it shudders of the line from a dead stop, never did before till i put lift on. does this help anyone, cause i want to fix this. thanks.

 

[ceastmen]

I don't know about your driveline setup (I've got the quad cab, long bed, 2500, with the 48re) but the carrier bearing on my truck is loosely constrained by the rubber mounting system. I don't approve, I know it's probably rubber mounted for vibration damping, but gives up the ghost when the Cummins 600 puts out some ft. lbs.



All the tech could tell me is DC was looking at changing the size and angle of the mounting block which the carrier bearing is bolted to. (Sorry for the bad sentence structure).



Different size blocks translate to different angles on the driveline. My fear is - will it move the resonant point of the driveline system to a different rpm range - possibly in the upper rpm range - which will affect the highway performance. I'll keep you apprised. When I get an answer or a TSB I'll create a new post specifically targeted at the vibration.



Thanks guys!

 

[ceastmen]

Originally posted by JDerbedrossian

i just recently put 4 inch superlift kit on truck. it has 2 inch blocks for rear, first thing i noticed it shudders of the line from a dead stop, never did before till i put lift on. does this help anyone, cause i want to fix this. thanks.

You have axle wrap!



First let me say: I'm damn un-impressed by Superlift engineers! I had a pair of Superlift 5" springs on my 1979 Dodge 3/4 ton and it had SEVERE axle wrap. I expected some - but this shook the truck uncontrollably!



I welded a member to the axle which had an arm that ran the LENGTH OF THE BED to a point on the frame near the transfercase and constrained it at the end of the arm from circumferential motion - i. e. I added a big lever arm (or ladder bar) to counter act the axle wrap motion. It didn't help much.



The further you move the axis of the rear axle vertically from the line-of-action of the rear leaf spring the more torque (bending) you will apply to the spring. As the spring begins to bend under loading (torque as a reaction to the pinion gear trying to "ride up" on the ring gear) the spring deflects to a point and then snaps back and resonates because the system is under damped.



It may help to add ladder bars to the system to help distribute the torsion the springs are experiencing.



Another thing to keep in mind is when the tires turn they apply a forward horizontal force to the axle via the bearings, the axle then pushes on the spring, and the spring pushes on the frame of the truck - right - so when you move the axle away from the truck the system that translates the force from the axle to the frame of the truck must be strong. The stronger the system the stiffer the ride!



Whew that was a long one! let me know if you need any assistance.

 

[ChrisKringle]

I think ur right. Four link setup with airbags WILL fix the problem of "axle wrap". Besides, stock ride just sucks **%#!