tl;dr the rear shocks don't fit, but the springs do, as do the front struts/springs.

Tried retrofitting a set of take-off rear ZF-Sachs shocks and springs from an 18 on our '11. I like the ride quality better than the (worn) OEM shocks, and these were a good deal, so figured it was worth a shot, as others are putting GE8 aftermarket shocks and springs on the GK. Well the shocks are too long. The body of the shock is maybe 0.5" longer, no problem there, but the spindle rod makes the total length about 3" longer. Under compression it hits the bump stop a bit sooner, as the bump stop and cap assembly is much longer on the '18 shock. This isn't so much of a problem, however the total length would allow too much drop of the axle if the car hit a pothole or the car got airborne, and would rip the ABS sensor wire.

On the plus side, the springs are the exact same size, and are either a slightly stiffer rate, or my old ones feel softer due to 95k miles. The '18 springs definitely feel better. Now need to decide what to use for rear shocks.

Will be trying the '18 front struts to see if they fit, as soon as some other front end parts orders arrive.

 

Update - I'm in the process of installing the 2018 front struts (ZF-Sachs OEM Honda take-offs) on the 2011, and they are the same size as the 2011 GE8. They fit near perfectly. There is a slight difference in the mounting point for the brake line, it is clocked just a bit, but the brake line still bolts on, and also a slight position difference for the wheel speed sensor plastic clip, which you can carefully adjust along the wire. Other than that, it is a bolt-on, works perfectly, all the hardware is the same, as are the strut mount bushings.

 

That is interesting. So that implies the HFP springs will fit, as will the front shocks ... that said I think it would be a bit odd having softer shocks only at the rear ...

 

 

I lifted the 2011 and the 2018 and measured full droop of the rear axle.

From the frame rail at the rear spring mount to the bottom of the spring pan:
12 7/8" on the 2011
13 1/4" on the 2018, a negligable difference, so the GK springs work fine.

Shocks however are a different story.
from the unibody at the top of the shock to the center of the bottom shock mount bolt:
24 7/8" on the 2011
30 1/4" on the 2018

The upper shock mounting point on the chassis is much higher in the 2018, necessitating a longer shock rod. You could get by with lowering the 2018, but the inverse would not work - the GK shocks are simply too long for the GE, allowing for too much droop and would rip the ABS sensor wire for sure if the car got airborne, or if it were put on a lift and the axle dropped to full shock extension.

 

Good work on this.

Me, I'm looking to lift my GE8 a little bit, making more room for slightly taller tires. Was hoping one of the newer Fits suspension could do that. Looks like no.