NEED HELP Removal of lower control arm help, just need bolt sizes

WeaponX

Original poster
Member
Mar 23, 2019
212
Pittston, PA
Hi all I’m new here and have a quick question. I want to change my lower control arm tomorrow along with the inner and outer tie rod ends, anyway I’m assuming I have to take the axel off and the inner tie rod on the other side I took off with a pipe wrench (which I know isn’t perfect but it worked lol) anyway I was wondering if anyone knew what the size socket I need to take the bolt off for the axel and what size the bolts where (the big ones) that hold the lower control arm on? I just want to make sure I have what I need before I rip it all apart and go ah sh$& I need______! Btw I’m replacing the whole arm not pressing new bushings in. Thanks for all the help
 

Reprise

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Jul 22, 2015
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21mm. Make sure you torque them to spec. Also at the link (which was found via Google, using keywords: lower control arm bolts trailblazer )

One thing not mentioned...if you scribe the outline of the position of the existing LCAs before removing, it'll make it that much easier to put the new ones in a somewhat correct position (you'll need an alignment afterward, in any case)

Oh, and welcome!
 

WeaponX

Original poster
Member
Mar 23, 2019
212
Pittston, PA
Thank you for the reply. I don’t have a torque wrench and I have changed everything in the suspension (trust me I mean everything from upper control arms to ball joints to links etc) and I’ve never torqued anything. What is the worst case from not doing so? Is 21mm the size or the nut for the axel outside the rotor? Thank you for your time
 

WeaponX

Original poster
Member
Mar 23, 2019
212
Pittston, PA
P.S. as far as the alignment I planned on doing a backyard one myself until I can get it professionally done next weekend
 

Mooseman

Moderator
Dec 4, 2011
25,671
Ottawa, ON
The axle hub nut is 35mm. 36mm will also work. You will need a torque wrench, especially for the axle nut (103 ft/lbs) so as to ensure proper retention. The lower control arm bolts need a ton of torque. This should help:

87927
 

16vcabman

Member
May 10, 2018
113
Ortonville, Mi
Why are you removing the axles to do lower control arms? I have never done this before. You drop the ball joint and shock mount at a arm. Then unbolt bracket from A-ARMS. Pull A-ARMS out and then bracket.
 

Mooseman

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Dec 4, 2011
25,671
Ottawa, ON
You have to undo the axle nut to have enough clearance to get the ball joint stud to clear the lower knuckle. Same as replacing the lower ball joint.
 

WeaponX

Original poster
Member
Mar 23, 2019
212
Pittston, PA
Now see when I replaced the lower ball joint I didn’t remove it nor did I use a ball joint press for top or bottom ball joints (so much easier and quicker with a metal bar with a hollow middle and a mallet and just pounding them in and out, all four done this way), anyway I’ve never done a lower control arm and the YouTube videos I did see all referenced Taking it off.
I didn’t get to it today but will and will post if I needed to remove it or not, I am going to try first not too
 

littleblazer

Member
Jul 6, 2014
9,267
Be sure to not break your bolt off in the frame nut like I did... that was fun. If it doesn't go, heat it. Trust me, the retention nut doesn't exist...
 

WeaponX

Original poster
Member
Mar 23, 2019
212
Pittston, PA
Thanks I hope it doesn’t break off. I put this off till this Saturday better weather but I forgot to ask, I’m changing the inner and putter tie rod ends, on the other side I got lucks and a small pipe wrench removed the inner tie rod end but Incase my luck doesn’t continue (which it never does) what tool is used to remove the inner tie rod end? Really thanks guys for all the help I really appreciate it all
 

Reprise

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The pipe wrench is what most ppl use on those, I think. Use thread locker on those, too. And you'll likely need to put heat on the existing ones to break the factory red locker on those nuts. A couple of minutes w/ a propane torch is enough.

Finally, you can rent ball joint kits, etc., for free at major parts chains. Having the right tools doesn't then require 'luck', either in the R&R of those parts, or in hoping they're not compromised & give way, putting you, family, and others at risk. Just a thought.
 

Maverick6587

Member
Dec 16, 2018
730
Sterling Heights, Michigan
Thank you for the reply. I don’t have a torque wrench and I have changed everything in the suspension (trust me I mean everything from upper control arms to ball joints to links etc) and I’ve never torqued anything. What is the worst case from not doing so? Is 21mm the size or the nut for the axel outside the rotor? Thank you for your time
Please go rent a torque wrench from an auto parts store. At least for the axle nut and your lug nuts. Too tight on either and you can burn out your wheel bearing.
 

littleblazer

Member
Jul 6, 2014
9,267
Please go rent a torque wrench from an auto parts store. At least for the axle nut and your lug nuts. Too tight on either and you can burn out your wheel bearing.
The axle nut sets no preload on the hub assembly... it goes through the center race. I suppose you could deform it by overtightening it but that would show other problems as well. 2wd trucks use the same hub with no axle... so it shouldn't kill the bearing.
 

WeaponX

Original poster
Member
Mar 23, 2019
212
Pittston, PA
The ball joints both upper and lower have been replaced and the kits as nothing more than a PITA a couple good hits and they popped right out and went in with ease.
I have an impact gun for the lugs and I can’t see how I could possibly tighten the axel bolt enough to destroy the bearings (which I think are bad and my next project) but I could be wrong.
I plan on getting a torque wrench this weekend and going over all the bolts I’ve done in the past just to be safe.
I know a lot but I need to learn a lot so I’m grateful for all the help from you guys, thank you
 

valk25

Member
May 6, 2019
4
usa
Be sure to not break your bolt off in the frame nut like I did... that was fun. If it doesn't go, heat it. Trust me, the retention nut doesn't exist...
Well, even with heat that front bracket bolt broke off on me. Any suggestions how to get this broken bolt out?
 

littleblazer

Member
Jul 6, 2014
9,267
Well, even with heat that front bracket bolt broke off on me. Any suggestions how to get this broken bolt out?
Hammer on the broken stud to pop the retention nut through the frame. I used vise grips and map gas after it was out to remove what was left of the stud and reuse the nut.
 
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littleblazer

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Jul 6, 2014
9,267
Should look something like this when done...
20170508_152712_1494271869395.jpg
 

valk25

Member
May 6, 2019
4
usa
Hammer on the broken stud to pop the retention nut through the frame. I used vise grips and map gas after it was out to remove what was left of the stud and reuse the nut.
Ok, am I understanding that there's also a nut in the frame? Or is the thread on the frame? I plan on getting a new bolt from the junkyard. Can't get the bracket out because it's getting hung up on the remaining part of the bolt. Thought about removing the sway/stabilizer bar and mount to access the top of the bolt. This is what my bolt looks like (below). I'm a female with basic skills, so I appreciate any suggestions .
 

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Mooseman

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Dec 4, 2011
25,671
Ottawa, ON
The nut is welded to the frame. If you can access it from the top, best is to heat it red with a torch and turn the remains of the bolt out, if it's accessible from the top. Alternatively, again if it's in an accessible spot on top, punch it out and use a regular nut. The front ones are accessible like that for sure, not sure about the rear ones though.
 

littleblazer

Member
Jul 6, 2014
9,267
Ok, am I understanding that there's also a nut in the frame? Or is the thread on the frame? I plan on getting a new bolt from the junkyard. Can't get the bracket out because it's getting hung up on the remaining part of the bolt. Thought about removing the sway/stabilizer bar and mount to access the top of the bolt. This is what my bolt looks like (below). I'm a female with basic skills, so I appreciate any suggestions .
So laying under the car looking up at the frame rail and bracket you can see the sheared part of the bolt. What I did was take a punch or chisel... what ever let's you get a good blow on the snapped part of the bolt, and use a big ass hammer to drive it out. It should go pretty easy. You can fish the bolt through the frame rail then and either replace the nut with a regular one or try and save it by using vise grips like I had done. I attached a crude drawing to illustrate. I used a chisel that was slightly smaller than the alignment notch.
The nut is welded to the frame. If you can access it from the top, best is to heat it red with a torch and turn the remains of the bolt out, if it's accessible from the top. Alternatively, again if it's in an accessible spot on top, punch it out and use a regular nut. The front ones are accessible like that for sure, not sure about the rear ones though.
Trust me... it's not welded... it's some oddball press in taper thing. Mine popped out with a few blows of a hammer. Unless you're referring to the rear. That to me looks like the front though. Idk.
20190509_150520.jpg
 
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WeaponX

Original poster
Member
Mar 23, 2019
212
Pittston, PA
I got lucky I guess not one of the bolts broke, no heat needed and they all on both sides came out pretty easy so I’m assuming sometime before I got someone was working on them since they were so easy to remove.
As far as getting it out I’d drill threw it if all other options fails because at the end you might have to retired to bolt hole
 

mrrsm

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Oct 22, 2015
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Congratulations on your success. But because these Badly Rusted Fasteners can often be snapped off so easily during this R&R and are so difficult to replace... FWIW... If you have not as yet re-installed them... Others would probably appreciate knowing what the Dimensions of the Bolts are that you've successfully removed and what they look like. Armed with that accurately recorded data... those Bolts can then be obtained here:


Overall Lengths
Partial Thread Lengths
Un-threaded Shank Lengths between the undersides of Bolt Faces to the start of the Thread Lines
Metric Markings on the Top Face of the Bolts
Metric Dimensions for Pitch and Thread Count... ex: M10 X 1.50 X 75MM Course Thread vs. having Fine Threads @1.25, etc.

While this VOP (Video Original Poster) has produced a Great Series about how to perform Major Front Suspension Repairs via a Complete Suspension Swap... He shows precisely Where and what Fasteners for the LCAB (Lower Control Arm Bracket) are involved at 5:40 into Video #4 of his Multi-Part Suspension Repair series:


 
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valk25

Member
May 6, 2019
4
usa
Thanks for the suggestions guys! Gonna be working on it more over the weekend. Fingers crossed this goes easily! This was a lot more labor than I thought it was going to be. Anyone know if the back 2 bolts are the same size as the front?
 

littleblazer

Member
Jul 6, 2014
9,267
Thanks for the suggestions guys! Gonna be working on it more over the weekend. Fingers crossed this goes easily! This was a lot more labor than I thought it was going to be. Anyone know if the back 2 bolts are the same size as the front?
They're all the same for the lower bracket.
 

mrrsm

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Oct 22, 2015
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Tampa Bay Area
GM (LCAB) Lower Control Arm Bracket Bolt Part Number 1151857

11518576
M16 x 2 x 70

GMOEMBODYBOLT.jpg

Image Credit Courtesy @Eric04 's Post #4 at this Link:


From @seanpooh via this Link:

https://gmtnation.com/forums/threads/lower-control-arm-bolt-size.15628/

Tighten the Front Lower Control Arm Bracket Mounting Bolt to 265 N·m (195 Ft Lbs).

Tighten the Rear Lower Control Arm Bracket Mounting Bolts to 240 N·m (177 Ft Lbs). Install the lower control arm to the lower control arm bracket.

Install the lower control arm to lower control arm bracket mounting bolts.

Important:

Ensure that the lower control arm is parallel to the lower control arm bracket during the installation and tightening of the lower control arm mounting bolts and nuts. This will ensure correct alignment of the lower control arm bushings.

Install the Lower Control Arm to Lower Control Arm Bracket Mounting Nuts.

Tighten the nuts to 130 N·m (96 lb ft).
 
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gmcman

Member
Dec 12, 2011
4,659
I replaced my lower control arm brackets not too long ago, and torqued to spec.

That day I dropped it off for the alignment and reminded them of the torque values of those bolts.

First time I got on the brakes kinda hard they ended up doing another alignment...:cool:...as the bracket went backwards due to insufficient bolt torque.

Even after that 2nd alignment, I brought my torque wrench to triple check before I drove it.
 

seanpooh

Member
Jan 24, 2012
461
I've been where you were at gmcman when I didn't do my own alignments. Places such as belle tire and others will just set the toe and let you go.

Yes they have the reference websites to tell them if caster and camber is adjustable along with torque specs. But as most shops are, guys are getting paid flat rate or commission. Not much time is going to be spent on details.
 
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JarredBrink

Member
Jul 26, 2020
1
Canada
Hi guys, so same dread thing happened to me: the front lower control arm bracket to frame bolt nut broke loose from the frame. Now I cant remove the bolt as the nut keeps turning when turn the bolt. Does anyone know what size this nut is? I'm hoping to try to get a socket on top of it to keep it in place while I finish loosen the bolt, but I don't know the size. Already tried a pair of vice grips but they don't hold the nut.
 

TobyU

Member
Oct 31, 2019
34
SW Ohio
The axle nut sets no preload on the hub assembly... it goes through the center race. I suppose you could deform it by overtightening it but that would show other problems as well. 2wd trucks use the same hub with no axle... so it shouldn't kill the bearing.
Correct. This design does not preload or load the bearing at all. It's like many ford 4wd trucks too.
All you are doing is tightening the splined shaft of the cv shaft with the nut and squeezing a solid metal tube or sleeve in the hub assembly. So unless you strip it off, crack the nut, snap off the shaft....it won't make much difference. You don't want it to get loose though or it will click and pop.

THIS is UNLIKE most GM FWD cars and minivans as they do load the bearing and too loose they click and prob not good on bearing and too tight...the bearing life suffers...BUT with the average replacement low quality hub life being about 10-20 months.....how can you really tell anymore?????
 

TobyU

Member
Oct 31, 2019
34
SW Ohio
While we're on it....what is the easiest way to do these arms? I did a driver's side last year and it was a bear.
Did it on the ground with jack and stands but getting it twisted and getting shaft into hole or whatever it was I can barely remember was a pain.
I ended up using a 6 foot spud bar to pry it.
 

Mooseman

Moderator
Dec 4, 2011
25,671
Ottawa, ON
Mine was so seized and the top side nut was inaccessible so I wound up cutting it off with the torches. All I can suggest is try different sockets or wrenches.
 

littleblazer

Member
Jul 6, 2014
9,267
18mm sounds right. I had an adjustable that fit in there iirc.
 
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Aaronb

Member
Jun 5, 2023
3
Knoxville Tennessee
Hi guys, so same dread thing happened to me: the front lower control arm bracket to frame bolt nut broke loose from the frame. Now I cant remove the bolt as the nut keeps turning when turn the bolt. Does anyone know what size this nut is? I'm hoping to try to get a socket on top of it to keep it in place while I finish loosen the bolt, but I don't know the size. Already tried a pair of vice grips but they don't hold the nut.
Did you figure out this problem I am having it right now myself
 

6716

Member
Jul 24, 2012
833
How do you get the nut to stay in the frame after reinstall??
I think at that point it's kinda like any other nut, it just isn't secured to the frame any more. So I would put the bolt through and get the nut on the threads.
 

littleblazer

Member
Jul 6, 2014
9,267
I think at that point it's kinda like any other nut, it just isn't secured to the frame any more. So I would put the bolt through and get the nut on the threads.
That's what I did.
 

Mooseman

Moderator
Dec 4, 2011
25,671
Ottawa, ON
I wonder if they make U-nuts that big (also known as speed nuts)? Tried searching for M16 or 5/8" U-nuts and came up empty. I don't think there's a slot or an open side so I don't think that would work neither. They look like this:

PPC240-278_AW02


Might have to cut a window in the frame so you can put an open end wrench on the nut. I can't think of anything else at this point.
 

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