There has been some discussion about being able to run '10 or later shocks, Bilsteins in particular, on an 09 or earlier. There are two different part numbers of the shocks dependent on the year, and as Nestah has pointed out, there are two different lower eye sizes: '07 is 39.30mm wide and the '10 is 41.50mm.
Shown, the proper sized lower eye for the pre 2009 FJ Cruiser. Photo credit: NestahEdition. Many thanks.
So there are indeed pronounced differences. The question is: Can you put these later shocks on an older FJ?
Yes but, be prepared to do some work.
The stock shocks lower mounting eye width is 32.35mm by my measurements.
The Bilsteins for the '10 and later eye width is 35.06mm.
That's a difference of 2.71mm or 1.355mm per side too wide.
The bolt sleeve inside the lower eye, within the rubber bushing is different as expected:
The stock bolt bushing is 39.30.
The Bilstein bushing is 41.30.
That's a difference of 2.00mm or 1.00mm too wide per each side of the bushing.
My lower eye shock mounts in the Lower Control Arm (LCA) measured out to be 40.03mm wide.
So I chose to remove a total of 2.76mm or 1.38mm from each side of the eye mount and 2.04mm or 1.02mm from each side of the bolt bushing. The final sizes became 32.30mm for the eye mount and for 39.26 for the bolt bushing. These are both a tiny bit undersize to ease installation.
The upper side of the shock and spring match without mods from year to year.
Having a small machine shop of my own, I put the lower eye into my milling vice and with an endmill, removed the proper amount from each side. I supported the top end of the shock with an adjustable mill table jack. This went well, though it took some fiddling to get the shock leveled in the mill vice.
Milling down the bushing was more of a challenge. I looked at pressing out the bushing, but that looked less than promising. So how to hold the bushing, which is surrounded by rubber in the eye, still and solid in the mill? I ended up turning an expanding mandrel from 5/8" steel stock to fit inside the bushing, I then clamped the mandrel vertically in the mill vice within a vee-block to ensure that it was perfectly vertical. I slipped the bushing over the mandrel. tightened the mandrel and supported the long end of the shock with the jack. I did this for all four sides, which took some time to do.
Finally after everything was cut and measured out as expected, I sprayed all the cut surfaces with silver HammerRite paint which matched the Bilstien paint pretty well.
I did the removal and replacement of the front shock assembly using the "No Spring Compressor" method explained elsewhere on this site. Unbolting the anti-sway bar both from the control arm and from the bushing on the frame (only on the side you are working on) was the key trick that made this method a snap. You can slide the sway bar just a few inches toward the front of the FJ and those few inches make all the difference in getting the shock / spring in and out. It is not mentioned in the procedure though.
Finally, it would be be seemingly obvious that the rear shocks would be a straight swap. That is not the case. The Bilstein shocks have a thicker piston shaft than the stock unit I was replacing. Also, the hole in the upper frame mounts for the rear shocks on the FJs must change with the model year as well. The metal washer that sits on top of the lower rubber bushing at the top of the shocks has a flange that rises about 1.50mm above the metal washer, this flange fits into the hole in the frame mount.
This shows the diameter of the Bilstein bushing washer. The flange fits into a hole in the mount on the FJ, This flange shown is way too big to fit on my 2008.
I mentioned the different rear shock shaft diameter, that keeps you from simply swapping the stock lower bushing and washers from stock to the Bilsteins. The old ones are too small to fit the shaft.
This is the Bilstein washer sitting on the stock lower bushing. You can see the difference in both shaft diameter and flange diameter. The stock washer fits tightly around the rubber.
There is also not enough material to turn the Bilstein bushing washer to fit the hole in the frame. What I did, that seems to work, is to remove and swap only the upper washers and keep the Bilstein bushings and lower washer. Of course, the Bilstein bushings are bonded, perhaps actually molded, to both the upper and lower washers of the bushing! It took some work with a bench vice and a sharp chisel to separate the pieces without ruining the rubber, but the old washer, despite being smaller in outer diameter, fit the Bilstein rubber bushing well and the rest of the installation went as expected.
Shown here, on left, Bilstein lower bushing washer, on right, stock upper bushing washer (sits under the shaft nut) and above, the stock rubber bushing.
In conclusion, will the newer part numbers fit the older FJs? Yes, but you will need to dedicate some time and have the tools to do it. My method works, but if you don't have a mill and lathe you will have a hard time keeping things square and perhaps even melt the bushing in the front lower mount when grinding the parts. One silly millimeter doesn't sound like much to remove, but you will spend hours trying to remove that much material with a file!
Its not "Can You? But "Should You?"