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View Full Version : OBS Camber/Caster Knock-outs - how to tell if you have them.



Shwa Kid
08-21-2010, 10:15 PM
A lot of people on here ask about the knockouts and if they have them or not. I don't know if this has been covered here or not, but if it has I guess this will just disappear in a few days.
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.
http://i638.photobucket.com/albums/uu102/penguin_mulisha/P9160043.jpg?t=1282447587
http://i31.photobucket.com/albums/c381/g9m3c/Truck%20Drivetrain/sus7.jpg

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.
http://i638.photobucket.com/albums/uu102/penguin_mulisha/P9160048.jpg?t=1282447587
Here are the removed knock-outs:
http://i638.photobucket.com/albums/uu102/penguin_mulisha/P9160050.jpg?t=1282447827

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.
http://i638.photobucket.com/albums/uu102/penguin_mulisha/P9160040.jpg?t=1282448062http://i638.photobucket.com/albums/uu102/penguin_mulisha/P9160051.jpg?t=1282448062

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.

g9m3c
08-22-2010, 04:44 PM
Good write up/pics. Some people have complained about how hard they are to remove. Mine were easy as pie. I used a small hammer and a flat head screwdriver to remove mine. :lol:

Bad Ass Z71
08-22-2010, 04:55 PM
Mine were that easy too.

oldk1500
08-22-2010, 04:59 PM
Need to check mine. I've had two seperate shops say they could not get my truck aligned right and i "might need" camber bolts. Well I paid for new bolts but tires still wear bad on outside on both sides of truck. I'll check mine, could be the problem. Knock outs!

machinist09
08-22-2010, 06:09 PM
Ya, I hate how vague the shop near me was. "You might need the knock-outs punched out." "Ok, how much $$?" "Uh...". Now that I see what all is needed, I'll do it myself, and drive the 1mi to the shop for an alignment right away.

oldk1500
08-23-2010, 05:01 AM
My shops didnt even refer to the knock outs! They said maybe the frame was bent.(could be, truck was wrecked before I bought it)

paladin
08-23-2010, 05:23 AM
Without going outside and looking at mine, I do remember that my 94 K1500 does not have a stamped/formed UCA. It is made from a solid round bar. Therefor I guess I don't have this issue. My front end guy has never mentioned anything about him not being able to align the castor/camber. Is this unique to K models?

someotherguy
08-23-2010, 07:39 AM
It's not a part of the control arm, it's part of the mounting pocket for it on the frame. Your 4x4, and even 2WD models from 8600GVWR up, have tubular-appearing arms which are actually forged solid pieces. Doesn't make any difference in regards to the knockouts. The reason your guy hasn't mentioned them - yet - it's not required to remove these for an alignment, until the amount of adjustability exceeds a range where the knockouts need to be removed in order to attain further adjustment. It'll get there one day.

Richard

paladin
08-23-2010, 08:12 AM
Thanks. Good to know.

NEUMANNZZ
08-23-2010, 12:19 PM
looks like that control arm needs a good sandblast and some new paint. :lol:

Shwa Kid
08-23-2010, 03:13 PM
looks like that control arm needs a good sandblast and some new paint. :lol:

I removed most of the rust, not on top of the priority list right now.

g9m3c
08-23-2010, 03:43 PM
I removed most of the rust, not on top of the priority list right now.

Slacker. :read:


http://i31.photobucket.com/albums/c381/g9m3c/Truck%20Drivetrain/sus6.jpg


:colby04:


I will admit that it took me as long to clean/prep/prime/paint my control arms as it did to do the rest of the front end rebuild. :lol:

Shwa Kid
08-23-2010, 04:07 PM
LOL I was admiring your control arms in your build thread... I should have taken pics of the other side, they're painted :LOL: Part of my time crunch in getting my truck back together, that side didn't get painted, it looks bad but it's functional.

g9m3c
08-23-2010, 04:14 PM
LOL I was admiring your control arms in your build thread... I should have taken pics of the other side, they're painted :LOL: Part of my time crunch in getting my truck back together, that side didn't get painted, it looks bad but it's functional.



I know where you're coming from. My frame got sprayed off with brake cleaner and coated with one heavy coat of semi-gloss black. :lol: It won't last long, but I can always re-do it later and it looks fine for now.

SimpleGreen
08-23-2010, 04:23 PM
I just looked at my step side and it appears that mine have already been done (looks like cam bolts). Good thing, too. The alignment shop wanted double the price if they weren't done. I was gonna tell them they better just index the wheel, straighten out the toe, and leave everything else the hell alone :lol:

kien chou
08-31-2010, 11:21 PM
question for shwa kid do you have to separate upper balljoint stud before removing upper control arm bolts

454cid
08-31-2010, 11:27 PM
The very first time I got an alignment the shop asked if I had ever had an alignment, and stated that if I hadn't, it would be more expensive becasue they'd have to remove the knockouts. I don't recall what the charge was, but it was kind of a lot. Looking back on it, they viewed the design as an extra money maker.

Shwa Kid
09-01-2010, 12:23 AM
question for shwa kid do you have to separate upper balljoint stud before removing upper control arm bolts

No, I did remove the 2 bolts that hold the brake line in place to get a little more movement, that way I could just move the upper control arm around, pivoting it on the ball joint.

Shwa Kid
09-01-2010, 12:39 AM
The very first time I got an alignment the shop asked if I had ever had an alignment, and stated that if I hadn't, it would be more expensive becasue they'd have to remove the knockouts. I don't recall what the charge was, but it was kind of a lot. Looking back on it, they viewed the design as an extra money maker.

That's not necessarily true. When the trucks all left the factory, they all had brand new parts and were all (approximately) exactly the same. With all new parts, the camber was guaranteed to be within spec when at that particular position in the UCA mount so there really was no need to adjust it at the factory. By not having to do an alignment, they saved a couple minutes off of the assembly time, reducing the cost of production and the cost of the vehicle. Seeing as the last of these trucks rolled off of the assembly line over 10 years ago and people are still taking out their knock-outs, I think it was a good cost saving measure, which likely was not of any detriment to the original owners of the vehicles.

SlvrdoHDmax
09-01-2010, 12:47 AM
Had mine done a few weeks ago for $125 total, alignment included. I knew how to do it but just didnt feel like doing it. Just like that u joint i need to replace..

454cid
09-01-2010, 12:49 AM
That's not necessarily true. When the trucks all left the factory, they all had brand new parts and were all (approximately) exactly the same. With all new parts, the camber was guaranteed to be within spec when at that particular position in the UCA mount so there really was no need to adjust it at the factory. By not having to do an alignment, they saved a couple minutes off of the assembly time, reducing the cost of production and the cost of the vehicle. Seeing as the last of these trucks rolled off of the assembly line over 10 years ago and people are still taking out their knock-outs, I think it was a good cost saving measure, which likely was not of any detriment to the original owners of the vehicles.

I understand that, my point was that the shop saw an opportunity and capitalized on it. By removing the knock-outs automatically, gained them more money, because it was something they could identify to the customer and charge more. Plus, it gave them more freedom on the alignment rack, if they needed it.

Shwa Kid
09-01-2010, 01:13 AM
I understand that, my point was that the shop saw an opportunity and capitalized on it. ...

I misunderstood you, I thought you meant General Motors when you said "they" in your previous post. It most certainly is a good opportunity for a shop to capitalize and make some money, if it's something that needs to be done, that's just the way it goes.

Helomedic1171
09-25-2010, 10:48 AM
so here's a question - how do you physically adjust the caster independently of the camber? the shop I took my truck to said they couldn't get the caster within spec, so now my truck pulls to the right quite a bit. I checked the brakes, and no joy there. My ball joints, tie rods, and adjusters, as well as the pitman and idler, are all new. I replaced the gearbox around that time also. It firmed up the steering a LOT, but it has always had a pull. I'm thinking either A) the shop doesn't know what they're doing, either in general or with my truck, or B) there's something else going on. I asked about the knock-outs and they said they've been done, plus there is a bolt with an eccentric washer on both sides in the upper control arm. after reading this, MY questions are: is it possible to have the eccentric washer in the UCA but yet NOT have the knock-outs done? and if not, what are the possible causes of the alignment issues?

Shwa Kid
09-25-2010, 12:26 PM
1)how do you physically adjust the caster independently of the camber? ...
2) is it possible to have the eccentric washer in the UCA but yet NOT have the knock-outs done?
3)if not, what are the possible causes of the alignment issues?

I edited that a bit to separate questions
1) You adjust the caster and camber together because one affects the other. You acjust the caster by moving one of the UCA mounts in/out more than the other, doing this affects the caster so you have to find the right balance
2) Yes, If someone is trying to pull a fast one on you, they could have just replaced the bolts with eccentric washers and the bolts that go with them. Are all of the cams in the straight up and down/neutral position? That would indicate that they're all centred and possibly not adjusted. I wouldn't count on it, but there is a possibility that it has happened.
3) Damaged parts possibly, something may be bent and you might not see it.. is the air pressure and tire tread equal between your front tires?

Also, what you said wasn't worded quite clearly, you have 4 eccentric cam bolt/washer combos right?

Helomedic1171
09-26-2010, 08:40 AM
1) You adjust the caster and camber together because one affects the other. You acjust the caster by moving one of the UCA mounts in/out more than the other, doing this affects the caster so you have to find the right balance
ok. that's what the tech at the shop was telling me. He'd move the tire to adjust camber, and it would throw off the caster, then he'd move to adjust caster, and screw up camber again, he could never get both where they needed to be. so he set camber within specs, and caster was left way out, because "Caster doesn't cause tire wear"... while that's true, I don't want to cause steering shaft or gearbox wear/damage because I'm constantly pulling firmly to the left to compensate.


2) Are all of the cams in the straight up and down/neutral position? That would indicate that they're all centred and possibly not adjusted. I wouldn't count on it, but there is a possibility that it has happened.
I glanced at this yesterday and thought the cams were straight up and down on the right side. This morning I checked again, and no, they appear to all be adjusted in different directions. so I would say the knock-outs have been removed.


3) Damaged parts possibly, something may be bent and you might not see it.. is the air pressure and tire tread equal between your front tires?
the tread is equal and the air pressure is also. I know the caster is way off because on the spec sheet one side is around 2 degrees and the other is .4 degrees. (don't remember the positive/negative). as for being bent, it's possible. most of the components around there are new, but what about my control arm bushings? could they cause alignment issues if they're bad? because mine look pretty ragged. and what about torsion bars? I never cranked mine, but the previous owner might have messed with them for all I know. how much would they affect the alignment? and if so, would switching to Ford keys make any difference at all?


Also, what you said wasn't worded quite clearly, you have 4 eccentric cam bolt/washer combos right? yes. :smile: I didn't make that very clear. there are 4 sets of cams/eccentric washers in my uppers. :D

Helomedic1171
10-01-2010, 04:43 AM
anyone?

Shwa Kid
10-01-2010, 06:43 PM
Well this is kind of above me but here's how I see it. If your UCA bushings are worn enough to cause excessive play (basically and measurable amount) then yes, they would give you trouble with an alignment. That trouble would show up in it being in spec at one point in time but out of spec at another because the bolts may rest in a different spot if the suspension loads and unloads. Cranking the torsion bars could cause too much negative camber (I think, maybe other way around) which would could make it so that when the camber is in spec, there isn't much room to play with caster.

I think I would consider going to a more experience alignment guy and have them take a look at it, something tells me that the person you went to just didn't have the patience to get them both in spec.

Helomedic1171
10-02-2010, 11:26 AM
so torsion bars DO affect alignment.... because if the bolts on my keys are any indication, they've been adjusted. I'll look into it more, and figure it out. You may be right - he just may not have wanted to work on it for a few hours to get it right, but I'll see if there's anything else contributing to it, and then go back. I really hate having to hold my steering wheel to the left.

djkurious
09-28-2012, 07:07 PM
Very informative information. I can tell the camber is positive on my 99 Tahoe with no mods. I took a look at the upper control arms and I see the cam on the control arm. It looks like the previous owner may already had the knockouts done. If it has the cam on the upper control arm resting on the bolt, would that indicate it was already done? I have a picture but have not met the post count as of yet.

Shwa Kid
09-29-2012, 08:14 AM
Very informative information. I can tell the camber is positive on my 99 Tahoe with no mods. I took a look at the upper control arms and I see the cam on the control arm. It looks like the previous owner may already had the knockouts done. If it has the cam on the upper control arm resting on the bolt, would that indicate it was already done? I have a picture but have not met the post count as of yet.

If there is a cam bolt at all, it would indicate the job's been done. From the factory, the truck only came with normal straight bolts. Cam bolts are only added once the knock outs have been removed.

*edit* see below post (by Quyonmob) for contrasting info.

Quyonmob
09-29-2012, 08:43 AM
If there is a cam bolt at all, it would indicate the job's been done. From the factory, the truck only came with normal straight bolts. Cam bolts are only added once the knock outs have been removed.

My 92 had cam bolts, and the knock-outs were still there. I punched the knock outs out and re-installed the cam bolts so they could actually do their job. Not sure if they were OE, but they sure matched the rest of the front suspension in appearance/rust, etc.

:dunno:

djkurious
09-29-2012, 03:12 PM
Well look like I will be removing the cams to see if the knockouts are actually there. Took it for a alignment and they said it could not be adjusted. I bet they didn't even check...

Shwa Kid
09-30-2012, 04:12 PM
My 92 had cam bolts, and the knock-outs were still there. I punched the knock outs out and re-installed the cam bolts so they could actually do their job. Not sure if they were OE, but they sure matched the rest of the front suspension in appearance/rust, etc.

:dunno:

Well it seems that I have been deemed to be wrong. :rolleyes:

stockchevy1983
09-30-2012, 05:46 PM
I went to get alignment done one day and they said my truck still has them and wanted to charge me 300 to knock them out.

Sent from my DROID BIONIC using Tapatalk 2

SUBURBIAN
09-30-2012, 07:17 PM
You can do it yourself with simple hand tools, a jack, & some stands...

mwall
09-30-2012, 09:32 PM
[QUOTE=Shwa Kid;5658613]If there is a cam bolt at all, it would indicate the job's been done. From the factory, the truck only came with normal straight bolts. Cam bolts are only added once the knock outs have been removed.

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.

TUFF-1892
01-11-2013, 03:50 PM
I know I am adding to an old post. BUT, I just dealt with this, and my truck DID HAVE CAM BOLTS FROM THE FACTORY, AND THE KNOCK OUTS WERE NOT REMOVED. I was a little confused because the original post with pics shows the OEM equipment without the round washers, and I guess I misunderstood the post.

SUBURBIAN
01-11-2013, 04:04 PM
I know I am adding to an old post. BUT, I just dealt with this, and my truck DID HAVE CAM BOLTS FROM THE FACTORY, AND THE KNOCK OUTS WERE NOT REMOVED. I was a little confused because the original post with pics shows the OEM equipment without the round washers, and I guess I misunderstood the post.

Did you get it set up right?

NEUMANNZZ
01-11-2013, 04:05 PM
see mwall's post above you it goes into detail and what was installed at the factory
.

speedracer326
01-11-2013, 04:15 PM
I went through this recently too. Mine had the eccentrics in there and I had to punch out the spot welded dealies to gain access to the adjustment slots, which provided for very little adjustment. I was quite disappointed. I think cranking the truck killed off some caster, as I was only able to get 1 degree of caster per side. I set camber at .5 degrees each side and made some fixtures specifically for my truck that enabled me to check toe with my toe bar. When I was done, the truck drove better and actually had more feel than before, so it must have been even more awful before. Someday when I have time, I'd like to modify the UCAs for some additional caster. Like another 6 degrees of caster. Ever seen an OBS with the wheel fully cranked maneuvering through a parking lot? Ever notice all that positive camber? That's caused by a lack of caster, GM obviously left room for improvement with the alignment.