I installed DJM rear shackles at the 1.5" drop position with zero drive line shudder about a month ago. Last week I had Belltech drop struts (1" drop position) & Belltech rear Street Perf. drop shocks installed and the shackles moved to the 2" drop position. The tech drove the truck after his work and thought he noticed some slight shudder at low speeds off and on so he installed 2 degree shims I had with the shocks. Here is where it gets interesting and my question.....after picking up the truck I noticed no low speed shudder but I now have a vibration between 75 and 80 mph that was NOT there before the install. If the pinion shims where not needed would they cause a vibration at higher speeds?? Conversely, do I need to install larger 2.5 or 3 degree shims? Any help is greatly appreciated.

 

It could just be that your alignment is off now.

 

It was aligned after the install. I have a before and after printout. The only thing that changed was the toe and it was corrected to .10 both sides. I'm swinging by in the morning and we are going to start with sliding the shims out and then drive it. We may have tried to fix a problem that was not there and created one with the shims.

 

2* shims for F150. But these cannot be a universal shim. Also make sure you have it installed correctly. Fat side of shim to the front of the truck

 

Fat side to the front? Positive? They have the fat side facing the rear. Would you not want to lower the front of the pumpkin to put it back into better alignment once lowered? That would be done by installing the shim with the fat side towards the rear of the truck to push the axle down at the u-joint.......correct?

The shims are the Belltech part number listed for the truck.....P/N 4975 but the tech did have to elongate the center slot for them to sit on the spring perch in the correct position.

 

On the F150s I have recommended it that way and it works. The 09+ had a suspension change so we are learning things as we get customer feedback.

 

That only makes sense because the shop that did the install drove the truck after it was lowered but before the shims we're put in at my request and said there was no vibration and are recommending they be removed to see if maybe the shims are actually causing the vibration. So confusing.....

 

You can thank Ford for the troubles lol

 

The fat side goes to the REAR of the truck.

When you install drop shackles, the pinion is pointing slightly more towards the ground (relatively speaking). Installing the shim with the fat side towards the rear rotates the pinion back to the correct angle.

If you're confused by the conflicting information, please refer to the installation instructions.

If the shim is installed properly (fat side to rear), try removing them. I'm using shims with my shackles, but I don't know what degree they are. I have Ground Force shackles and they include the correct shims.

If however the shims are improperly installed (fat side towards the front), go back to the shop and bitch-slap somebody.

 

Not to hijack but I put 3" blocks on my 2010 and was told my pinion angles were off 2.5. I installed shims fat side to the rear thinking I needed to swing the front of the diff up. Are they in backwards?

 

No, on my 2" drop, fat side was to the rear. Put 135,000 on it that way.

 

Looks like even with the 2* shims the pinion angle is still of a little less than 2* so 3* shims are in order. This was double checked with a pinion angle finder.