13 Scab 5.0 4x4 shudder 25 mph to 15 mph on deceleration
 

I installed a 2" strut spacer (which added 2.5") on my the front of my truck, drove it about 25 miles and noted no issues.

Then installed pro comp add a leaf which added about 1.75". Also drove about 25 miles and noted a slight vibration or shudder (not always more than a vibration) difficult to pinpoint to front or back, during deceleration (braking or coasting) as the truck passes from 25 mph to 15 mph.

I had my front end aligned, and the problem is now worse. Shop cannot identify either, but they are an alignment shop only. They think it's driveline related.

Ford says it's the front end due to spacer and are basically done looking at it. I took out the spacer and add a leafs. Problem is still there just very hard to notice. Ford then said it's a characteristic.

I think the lift is making the problem more prevalent but it may be a pre existing condition on the truck.

Anyone have an issue like this? Resolved? How?

Any help appreciated.

AAL and strut spacer are installed again, problem is quite noticeable. Have done all the basic trouble shooting. With/without transmission engaged, 4x4, 4x2, e brake only, brakes, exterior observer watching while conditions are replicated. Have decided it is not felt through the steering wheel at all.

Have your tires checked for true and rebalanced.

Good call. Alignment shop has done so twice so far, no corrections needed either tie but they humored me.

A neighbor that works as a mechanic suggested the pinion angle. He looked at my truck and noted that just by eyeball it seems drag during deceleration conditions might drop the pinion angle further than the AAL alone has done. That might explain to him, why the issue occurs only on deceleration. He drove my truck and found it odd. No issues whatsoever at speed, acceleration, etc.

I'll get it on a four post lift and check driveline angles next week at a buddies shop. I'll see if he can find tire balance and truing issues during the same visit.

Trued, balance checked, alignment checked. Driveline angles off by 3.5 degrees. Ordering shims will update thread with results once installed.

Installed 2.5 degree shims (available without custom fab). 5 mile test drive and problem thus far solved. Will update thread if issue returns. Thanks for suggestion!