Knockouts on GM 4 wheel drive turcks with IFS.
You have what I'm calling two cam bolts where the upper A-arm mounts
to the frame, Two bolts on each side at the upper mount. These cam
bolts run throught the frame pockets (A-arm mounts) and through the
A-arm. They physically control the postion of the A-arm. So anyway
the holes in the two frame pockets are slotted (not sure of the right
word to use here but anyway) These frame pockets where the upper A-arm
mounts to the truck have partially slotted holes. These holes are
where the cam bolts are adjusted for
alingment purposes. From the factory they are only partially slotted
on one end. The knockouts are where you take a special "j-tool" or
other method to further open up the slots in these holes to allow for
additional adjustment on the alignment.
Bascially the Knockouts are where one removes some metal around the
cam bolt mounts holes in the A-Arm frame pockets to allow for
increased adjustment on front end alignments. If they do this they
have to remove the upper A-arm to get access to the mounting holes in
I believe they also want to sell you a "alingment kit" which to my
understanding are new cam bolts for the left and right upper A-arms
along with the matching washers and nuts.
I may have not used the correct termonology but its close. Hopefully
you get my intent.
I'm not sure if they have to knock out the "holes on both frame
pockets front and back or just partially. The holes look somewhat
oval with extra materal on the sides that would allow one to remove
these "special knockouts" to gain additional adjustment for alignment.
You really can't see these "holes" until you remove the cam bolts and
then then the upper A-Arm.
I'm no front end person but I believe some trucks require the
knockouts to be removed in order to get the vehicle alinged properly.