Pulling to the right when 4x4 engaged under acceleration

[benztech82]

Hey guys,

I got a weird issue which became more noticeable after i did a lift.
Truck is pulling really hard to the right when i hit gas pedal. No issues when coasting, braking or when i'm in rear wheel drive mode. I have new lower control arms, links, balljoints are all good, new front wheel bearings and tires are coopers st maxx with 20k on them. Both front driveshafts replaced 40k ago.

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[xtremewlr]

Sounds like the axle isn't fully engaging then. Get the wheels off the ground with the truck in 4wd and turn the front wheels by hand and see if they both turn.

The right axle is the one with the disconnect so it seems odd it's pulling to the right. But it sounds like something in the front diff or the axles somewhere. Tcase sounds like it's working just fine since you are getting power to one of the wheels at least.

 

[codeman528]

I had a very similar issue a while back! Thought maybe it was my rear control arms so I replaced all 4 and it got a little better, but not solved. Ended up getting my wheels and tires balanced and then rotated because I was was having a vibration issue, and that resolved it for me :shrug: I was boggled but happy the problem was gone. Might be worth a shot!

 

[duffdog]

Yes.

This happens by design. It is called the "Thrust Angle" and is built into truck from the factory. The rear diagonal control arm (panhard bar) is designed to minimize the thrust angle changes under acceleration by describing an arc close to zero degrees under acceleration as the truck pitches rearward. Lifting the truck causes the arm to describe an arc with a negative value that moves the axle to the driver side under acceleration and back to the passenger side when driving straight. Aligning the truck to factory specs cannot accommodate for the changes in rear suspension geometry when under load. Thus the alignment is wrong under acceleration and correct when traveling under low engine load scenarios. The higher you lift the rear of the truck, the worse it gets.

You can get panhard mount weld-on extensions.

I think a better solution would be to install a fully parallel 4 bar linkage that uses the existing mount and does not involve any weldling.

 

[benztech82]

Yes.



This happens by design. It is called the "Thrust Angle" and is built into truck from the factory. The rear diagonal control arm (panhard bar) is designed to minimize the thrust angle changes under acceleration by describing an arc close to zero degrees under acceleration as the truck pitches rearward. Lifting the truck causes the arm to describe an arc with a negative value that moves the axle to the driver side under acceleration and back to the passenger side when driving straight. Aligning the truck to factory specs cannot accommodate for the changes in rear suspension geometry when under load. Thus the alignment is wrong under acceleration and correct when traveling under low engine load scenarios. The higher you lift the rear of the truck, the worse it gets.



You can get panhard mount weld-on extensions.



I think a better solution would be to install a fully parallel 4 bar linkage that uses the existing mount and does not involve any weldling.

Um...alignment fixed it today.

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[duffdog]

Um...alignment fixed it today.

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Ok. Your truck must not have much of a rear lift.

 

[benztech82]

Probably not, 1.5" daystar with 2.5" OME spring and 5100.

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