SCOTTYINWV
si vis pacem, para bellum
This info is borrowed from fullsizechevy.com. I searched for an info here, but came up empty.
What the knockouts are: When the OBS trucks left the line, you couldn't adjust the camber or caster because the upper control arm mounts were fixed. On side of each mounting point had a circular hole, and the other was slotted. This allowed the factory workers to just slide the bolts in without doing a full alignment, they were close enough to spec. Provisions were made to allow for future camber/caster adjustment and these were known as "knock-outs". Basically all they were was an area that could be punched out around the circular UCA mounting hole to elongate it to a slot, allowing the UCA to be moved inward/outward. Seeing as the camber and caster weren't adjustable from the factory, a hardened bolt was used to hold the UCA rather than a cam bolt. To adjust the camber/caster or OBS trucks, you must remove the knock-outs and install the cam bolts (GM calls this "Camber and Caster adjustment kit No.15538596")
The easiest way to tell if your truck still has the knock-outs in tact is to check and see if you have hardened bolts holding your UCA's in or if they are cam bolts. If you have the cam bolts installed, that means the camber/caster has been adjusted on the truck and the knockouts have been removed. - This is not definitive to confirm they have been removed as the PO could have done a number of things, it should confirm only if they have NOT been removed.
The most definite way to check if your truck has the knock-outs still is to remove the UCA and visually check for them. To do this, jack up the vehicle and SUPPORT IT ON THE LOWER CONTROL ARM. This is very important as it keeps the tension on the spring but relieves the load from the upper control arm. You can now remove the upper control arm bolts and look at the holes to check if they are round or slotted. Only 2 of the 4 holes on each UCA will be round, these being the front holes of each mount. Here is what a knock-out that has not been removed should look like, in this picture you can also see the outline of the knockout, which will be removed. First picture is the knockouts on my 89, the second is G9M3C's on his 93, as you can see, they're slightly different.
To remove the knock-out, use your pick of removal tool and hammer it out. (I used a punch and chisel, but an air chisel would work well too.) *EDIT* I just found out that there is actually a tool made for doing this, it uses a threaded rod through the UCA mount that you can tighten against the knock-outs and eventually break them off. */EDIT*Here's what a completely removed knock-out should look like. You man need to file the edges a little to allow for proper cam-bolt actuation. Also note that sometimes the knock-outs don't come out all in one piece and are only partially removed. Make sure the whole knock-out is removed for full alignment potential.
Here are the removed knockouts:
Before you re-install your UCA, install the cam bolts and ensure full travel, just to be sure there aren't any hang-ups.
For reference, here is a picture of a UCA with just the bolts, the way it came from the factory and a picture of the cam bolts installed.
You shouldn't need to remove your fenders like I did, but I decided in favor of it for the space and because I had to gap them anyways.
If you have any questions, ask away.
*Edit Jan 13/13
Here's a quote of mwall from page two, added it here because this post is misleading/wrong with regards to using the existance of cam bolts to determine if the knock outs have been removed. (My info was specific to 88-90)
"1988-1990 GM CK trucks came from the factory with straight bolts and had spot welded washers over the adjustment slots. In 1991 GM updated the CK trucks with greaseable ball joints and they came from the factory with cam bolts installed but the adjustment slots were indented and the "knockouts" needed to be removed for adjustment. When dealer inspecting brand new 1991 and newer trucks I remember that many came from the factory with the driver side cams straight up and the passenger side cams straight down. Starting in 1996, GM didn't indent the adjustment slots as well as on the previous trucks so to make them easier to remove (in their opinion), they slotted the knockouts from the factory which made them bend and tear during removal with the GM special tool knockout remover making a die grinder neccesary many times."
Link to the original thread on fsc:
http://www.fullsizechevy.com/forum/...ter-knock-outs-how-tell-if-you-have-them.html
I have to check my truck in the morning since I need an alignment.
And again, this is gathered info from another forum. I'm not claiming it as mine, and give all of the credit to them!
What the knockouts are: When the OBS trucks left the line, you couldn't adjust the camber or caster because the upper control arm mounts were fixed. On side of each mounting point had a circular hole, and the other was slotted. This allowed the factory workers to just slide the bolts in without doing a full alignment, they were close enough to spec. Provisions were made to allow for future camber/caster adjustment and these were known as "knock-outs". Basically all they were was an area that could be punched out around the circular UCA mounting hole to elongate it to a slot, allowing the UCA to be moved inward/outward. Seeing as the camber and caster weren't adjustable from the factory, a hardened bolt was used to hold the UCA rather than a cam bolt. To adjust the camber/caster or OBS trucks, you must remove the knock-outs and install the cam bolts (GM calls this "Camber and Caster adjustment kit No.15538596")
The easiest way to tell if your truck still has the knock-outs in tact is to check and see if you have hardened bolts holding your UCA's in or if they are cam bolts. If you have the cam bolts installed, that means the camber/caster has been adjusted on the truck and the knockouts have been removed. - This is not definitive to confirm they have been removed as the PO could have done a number of things, it should confirm only if they have NOT been removed.
The most definite way to check if your truck has the knock-outs still is to remove the UCA and visually check for them. To do this, jack up the vehicle and SUPPORT IT ON THE LOWER CONTROL ARM. This is very important as it keeps the tension on the spring but relieves the load from the upper control arm. You can now remove the upper control arm bolts and look at the holes to check if they are round or slotted. Only 2 of the 4 holes on each UCA will be round, these being the front holes of each mount. Here is what a knock-out that has not been removed should look like, in this picture you can also see the outline of the knockout, which will be removed. First picture is the knockouts on my 89, the second is G9M3C's on his 93, as you can see, they're slightly different.
You must be registered for see images attach
You must be registered for see images attach
To remove the knock-out, use your pick of removal tool and hammer it out. (I used a punch and chisel, but an air chisel would work well too.) *EDIT* I just found out that there is actually a tool made for doing this, it uses a threaded rod through the UCA mount that you can tighten against the knock-outs and eventually break them off. */EDIT*Here's what a completely removed knock-out should look like. You man need to file the edges a little to allow for proper cam-bolt actuation. Also note that sometimes the knock-outs don't come out all in one piece and are only partially removed. Make sure the whole knock-out is removed for full alignment potential.
You must be registered for see images attach
Here are the removed knockouts:
You must be registered for see images attach
Before you re-install your UCA, install the cam bolts and ensure full travel, just to be sure there aren't any hang-ups.
For reference, here is a picture of a UCA with just the bolts, the way it came from the factory and a picture of the cam bolts installed.
You must be registered for see images attach
You must be registered for see images attach
You shouldn't need to remove your fenders like I did, but I decided in favor of it for the space and because I had to gap them anyways.
If you have any questions, ask away.
*Edit Jan 13/13
Here's a quote of mwall from page two, added it here because this post is misleading/wrong with regards to using the existance of cam bolts to determine if the knock outs have been removed. (My info was specific to 88-90)
"1988-1990 GM CK trucks came from the factory with straight bolts and had spot welded washers over the adjustment slots. In 1991 GM updated the CK trucks with greaseable ball joints and they came from the factory with cam bolts installed but the adjustment slots were indented and the "knockouts" needed to be removed for adjustment. When dealer inspecting brand new 1991 and newer trucks I remember that many came from the factory with the driver side cams straight up and the passenger side cams straight down. Starting in 1996, GM didn't indent the adjustment slots as well as on the previous trucks so to make them easier to remove (in their opinion), they slotted the knockouts from the factory which made them bend and tear during removal with the GM special tool knockout remover making a die grinder neccesary many times."
Link to the original thread on fsc:
http://www.fullsizechevy.com/forum/...ter-knock-outs-how-tell-if-you-have-them.html
I have to check my truck in the morning since I need an alignment.
And again, this is gathered info from another forum. I'm not claiming it as mine, and give all of the credit to them!