At a loss, Acceleration Shake

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CBenZ71

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Okay, needing some suggestions or directions to go with my truck.
When I take off from a stop, I get a shake that feelings like it is in the driveline(Maybe?) between 5-15 MPH. After passing 15 MPH it goes away and drives fine. It does it when it is cold, hot, doesn't matter.
The truck is a 1999 K2500 4Door, 85000 original miles. 7.4L. 4.56 gears. 4 inch lift.
I have completely rebuilt the entire front end steering and suspension, all new bushings, bearings, shocks, every steering component is new. On the driveline, all 3 U-Joints are replaced and greased, and the center support bearing and rubber housing was changed. Replacing the center support bearing did reduce the shake a significant amount because the old rubber was completely trashed, but it is still there.
If you have any suggestions please send them my way!
 

Hipster

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Just a few things that come across my mind. Flat spot/out of balance/separated belt in tire? No mention of wheel bearings? Out of balance/run out on driveshaft? Engine/trans mounts?
 

RichLo

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What kind of lift in the back? Blocks or shackles? If its longer shackles your differential driveline angle changed
 

Frank Enstein

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Pinion angle, Bad ground, Fuel regulator leaking into plenum, and Fuel injector stuck are some that come to mind. Does it idle smoothly? Anything show up on a code reader?
 

CBenZ71

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What kind of lift in the back? Blocks or shackles? If its longer shackles your differential driveline angle changed
Its a block lift. I beleive the brand is TrailBlazer. Original owner had it done as soon as he bought the truck in '99.
 

CBenZ71

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Pinion angle, Bad ground, Fuel regulator leaking into plenum, and Fuel injector stuck are some that come to mind. Does it idle smoothly? Anything show up on a code reader?
Injectors are new from Five-O motor sports, Fuel regulator is also new. No codes showing up it is 0411 swapped. Idle is smooth no problems there. I can rev it in park/neutral and it revs greats does shudder at all which is why I was starting to think it was driveline/rear end related. How could I check pinion angle and whether or not it is correct?
 

CBenZ71

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Just a few things that come across my mind. Flat spot/out of balance/separated belt in tire? No mention of wheel bearings? Out of balance/run out on driveshaft? Engine/trans mounts?
Is there a way for me to check tire speration? I don't see any obvious signs of tire issues visually. Front wheel bearings are both brand new. I thought about the driveshaft many, but would it be smooth at high speeds if the driveshaft was unbalanced? I will have to take a look at the mounts to make sure they are okay, have not checked them yet.
 

Frank Enstein

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Injectors are new from Five-O motor sports, Fuel regulator is also new. No codes showing up it is 0411 swapped. Idle is smooth no problems there. I can rev it in park/neutral and it revs greats does shudder at all which is why I was starting to think it was driveline/rear end related. How could I check pinion angle and whether or not it is correct?
Pinion angle is easy to check. get an angle finder and put it on the bottom pulley to see how far from vertical it is. The put the angle finder on the front of the rear end yoke where the driveshaft connects. The pinion should be pointing slightly down compared to the pulley. Under load the angles should be the same. Because of the torque reaction trying to counter rotate the axle the pinion angle needs to be 2-4 degrees downhill at rest with leaf springs.
 

Frank Enstein

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For tread separation all you need to do is lift the tire off the ground so it can spin freely and look for the tire to be out of round or the tread moving side to side.
 

Nad_Yvalhosert

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Off the line acceleration vibration, after a lift kit with blocks? Your problem is your pinion angle. Lower the nose of the axle, it's too high.
 
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