Vibration and hum below 25mph after add a leaf

After installation of a leaf helper, I'm now getting a loud hum that peaks at 24mph and vibration below that. The only change made was adding a leaf spring to raise the back a little. It's advertised as a 1" lift.

My alignment on the back is slightly off. I'm planning on doing that in the next couple days.

 

I would highly recommend you try these 3 degree shims. I had a NASTY vibration around 45-55 MPH after I lifted my Tacoma. Tried the carrier bearing drop solution, no luck. Road forced balanced and rotated all wheels / tires. No luck. Then found these - THANKS TO THIS FORUM - ordered and installed and POOF the vibration went away instantly.

These correct the pinion angle back to where it needs to be. HTH

 

what do you mean your rear alignment is off? Is this from measuring front to back axle on either sides? you can nudge things a little but the only real alignment concern is the leaf pin being fully seated in the axle mount hole. we don't have cam adjustments in the rear like crossover or AWD vehicles

 

I was also going to question that. But I left it alone. It's a solid rear axle. How on earth is it out of alignment?!?!?!

As a Ford Mustang fanatic and owner, it is widely known the rear differential (axle) tends to shift an inch or so towards the passenger side when people lower them. But Ford Mustangs do not have leaf springs in the rear. And you can easily correct the shift with any one of the half-dozen or so aftermarket adjustable panhard bars.

These trucks don't even have a panhard bar.

OP:
I have a sneaking suspicion that you bolted everything up TIGHT while your truck was still hoisted in the air. This will cause issues and maybe even be the cause of your vibration.

The leaf spring assemblies need to be installed only with the bolts being snugged up. Then the vehicle has to have to the suspension loaded with the weight of the truck before you torque everything to spec.

There is also a small dowel pin that needs to be correctly seated. If you didn't get that right, it could be causing issues.



I would certainly try loosening all the bolts and gently rolling your truck a few feet in each direction to see of that gets things to settle into proper position. Something is not right here. I would absolutely be at least performing a check of the above.

You may need those shims I suggested above - but they are usually only necessary if you have lifted your truck 2.5 inches or more.

HTH and good luck!

 

Also, its my understanding that the U bolts will stretch a little when properly torqued.
It doesn't have an X in the manual indicating single use but it may be a part you want to avoid re-using.