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Blazer Body Mount Bolts & Body Lift Info.

colbystephens

colbystephens

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I searched and searched before doing my body mounts and lift today for definitive info on CK5 for the body mount bolts for my K5, and I didn't come up with anything I felt I could trust. So, here's the deal:

Stock body mount bolts on a '90 K5 are:
  • Grade 5, 1/2 diameter, 13 thread count.
  • (2) at 6.5" long carriage bolt (rear most bolts)
  • (2) at 3" long carriage bolt (bed bolts)
  • (4) at 3.5" flange bolt (or regular with SAE washers - 2/side under the rockers)
  • (2) at 5" flange or reg + washer for core support.
  • If you're replacing the nuts, you'll need 6. The other four are captured nuts.

I'm assuming this info is true of all the V-series Blazers, and probably also for earlier K-series Blazers, at least back to 1981. I use that as my cut-off date for reliability because I used a Daystar body mount bushing kit that was for K5s from '81 to '91. Since I used a 1" body lift, I added 1" to those lengths for my replacement bolts.

Stock Bolts, you'll notice the carriage bolt on the left has a nut welded to it because it was spinning:

IMG_20130628_122436_194 by colbyjstephens, on Flickr

No body-lift:

IMG_20130628_124113_663 by colbyjstephens, on Flickr

With a 1" body lift. Big difference, Right?:

IMG_20130628_172712_559 by colbyjstephens, on Flickr

Half-way progress pic for laughs:

IMG_20130628_150004_710 by colbyjstephens, on Flickr

The process, which is abundantly available online elsewhere (and here on CK5!):

Fortunately for me, I live in a desert that sees rain a couple days a year. So, while some of my bolts were a bit crusty, the job wasn't as miserable as it would be in other locales. Basic premise: Loosen all the bolts, then remove all the bolts from one side. Put a hi-lift jack under your slider (or stick a 4x4 behind your rocker panel), and lift that side up high enough to get the mounts out. Note that, at least with the Daystar kit, you'll reuse the metal sleeves that are in the rocker-mount bushings. Otherwise, there's new sleeves for the other two locations that require it. Then, loosely reinstall your hardware and do the other side. You'll probably have to fuss with the bushings in the cups to get them out - I used a couple of pry bars. One was really stuck, so I cut it out with a cutoff wheel. After you get them all installed, torque them down properly.

Why do this?

I'm into making my truck a bit more comfortable for passengers on the harsh NV backcountry trails (think dry riverbed... everywhere!), and so I was thinking that making sure my body mounts are in top shape would be important. I figured I'd also put a body lift in at the same time to make my tires clear the fenders at full-stuff.
 
Good job Colby. Now come on down and help me install my body mounts that I bought 5 years ago and still reside under my tool box.
 
You'll find it makes it easier to work on things underneath the truck as well.

Martin
 
I just finished replacing the mounts on my 1986 Suburban with Daystar mounts. Took 3 days. This truck lived in Georgia it's whole life. There was not much left of many bolts due to corrosion. Scary!

It made a huge difference in ride quality and noise.
 
I had to do mine because the back 4 had rotted out and the ass end was jumping around like a fish outa water. Made a huge difference with all poly mounts.
 
This has been on my "long term" list of projects, kinda scared about the whole thing, lol.

Ive got my interior Line'X is this going to pose an issue if I were to do body mounts?

Isnt some of the carriage bolts hidden under other panels?
 
This is good info and this thread is one of those that should be in the Tech Articles section for easy to find future reference. :waytogo:

Maybe get a mod to move it? :dunno:
 
elyon said:
I just finished replacing the mounts on my 1986 Suburban with Daystar mounts. Took 3 days. This truck lived in Georgia it's whole life. There was not much left of many bolts due to corrosion. Scary!

It made a huge difference in ride quality and noise.
Click to expand...

Do you have your stock bolt information? If so, I'll add it to the first post.


I think my ride quality improvement will be marginal, as my body mounts weren't completely shot. Several of them looked new!


badmix said:
This has been on my "long term" list of projects, kinda scared about the whole thing, lol.

Ive got my interior Line'X is this going to pose an issue if I were to do body mounts?

Isnt some of the carriage bolts hidden under other panels?
Click to expand...

Possibly a problem. 4 carriage bolts go through the truck bed. If they're shot, or you're doing a body lift, you'll have to pull them. If the captured nuts under your rockers are stripped, you'll have to cut holes in the floor to get to them. Penetrating oil and an impact will help avoid these problems.
 
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I found the 2 carriage bolts in the middle of the bed to be spot welded in place. Ended up grinding the heads off. One of the 4 bolts that offer up from underneath the truck mid-cabin ended up spinning the nut. The nuts on those 4 are boxed in to hold them in place. mine did not hold. I used penetrant oil to no avail. I found behind the drivers seat a circular indentation in the floor over the bolt. I drilled it with a 1 1/2 inch hole saw and found it to be perfectly aligned with the bolt. I had to take out the pilot drill on my hole saw and free hand it because the bolt came right up to sheet metal underneath. I tried more penetrant oil overnight, but no luck. I ended up drilling down through the box and the nut and used the drill bit to pin it in place. after all that I was able to brake the bolt free. I had a 1 1/2 inch body plug to fit there.

I used a ram jack between the rear spring mount and the bolt right above it to drive the bolt up and out. I had to jack the truck up and use the body weight on the bolt to get it to finally break free. A bit of hammering from the top side with a ball peen hammer and an appropriately sized impact socket as well.

Similar setup on the most rear carriage bolts. Used an appropriate length bolt and jacket the body up as before. lots of hammering using the weight of the body again. It bent a grade 8 bolt I used pushing from the bottom wedged between the frozen carriage bolt and the frame.

The front bushings missed being removed by about an 1/8 of an inch when I jacked the body up as far as it would go at the front of the truck. I ended up using a tie down while the truck was not jacketed up to hook to the frame and then wrap around the front axle and back up to the frame. Cinched tight and then jacked the body up again. The suspension kept lifting the frame up when I jacked the body and wouldn't allow me to remove the bushing. It worked and I got it out.

2013-03-21 12.27.24.jpg
 
That sounds miserable, but your truck is looking good. Thanks to mentioning the spot weld, as I forgot.
 
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elyon said:
I found the 2 carriage bolts in the middle of the bed to be spot welded in place. Ended up grinding the heads off. One of the 4 bolts that offer up from underneath the truck mid-cabin ended up spinning the nut. The nuts on those 4 are boxed in to hold them in place. mine did not hold. I used penetrant oil to no avail. I found behind the drivers seat a circular indentation in the floor over the bolt. I drilled it with a 1 1/2 inch hole saw and found it to be perfectly aligned with the bolt. I had to take out the pilot drill on my hole saw and free hand it because the bolt came right up to sheet metal underneath. I tried more penetrant oil overnight, but no luck. I ended up drilling down through the box and the nut and used the drill bit to pin it in place. after all that I was able to brake the bolt free. I had a 1 1/2 inch body plug to fit there.

I used a ram jack between the rear spring mount and the bolt right above it to drive the bolt up and out. I had to jack the truck up and use the body weight on the bolt to get it to finally break free. A bit of hammering from the top side with a ball peen hammer and an appropriately sized impact socket as well.

Similar setup on the most rear carriage bolts. Used an appropriate length bolt and jacket the body up as before. lots of hammering using the weight of the body again. It bent a grade 8 bolt I used pushing from the bottom wedged between the frozen carriage bolt and the frame.

The front bushings missed being removed by about an 1/8 of an inch when I jacked the body up as far as it would go at the front of the truck. I ended up using a tie down while the truck was not jacketed up to hook to the frame and then wrap around the front axle and back up to the frame. Cinched tight and then jacked the body up again. The suspension kept lifting the frame up when I jacked the body and wouldn't allow me to remove the bushing. It worked and I got it out.
Click to expand...

good lord and that is why I havent tackled my body mounts. I think we need a "body mount swap get together"
 
I replaced all the stock bolts with grade 8 bolts. Even replaced the carriage bolts with standard bolts.
 
I also replaced the carriage bolts with regular ones. Grade 8 certainly will work well in this application, but is unnecessary, and I didn't want to spend the extra money on it. The body mount bushings take up the vast majority of the shear loading, so the bolts are there mostly to keep the bushings clamped together.
 
Use a air hammer on the bolts to help break the bolts free from the steel sleeves they go thru. That is what holds the bolts from coming out in the rear of the truck. Vibrating the bolts will shake all the rust free.
 
Massboy said:
Use a air hammer on the bolts to help break the bolts free from the steel sleeves they go thru. That is what holds the bolts from coming out in the rear of the truck. Vibrating the bolts will shake all the rust free.
Click to expand...

Just don't do this with your head directly underneath. This is the voice of experience, telling you that rust tastes bad :haha:

-- A
 
Resurrecting this thread since it seems to be one of the most comprehensive. A few questions: are the carriage bolts in back always tacked? I wasn't clear on that. My interior is Line-X'd, and I could see razoring the head free, but if it has to be ground down, that'll be more damaging. Also, no mention here about the ones under the radiator. Did you pull/move the radiator, or jack extra high, or what? Is the bolt under the radiator tacked, or free spinning? Thanks.
 
my K5 backs where tacked..

the front ones are bolts, and accessible from the front of the core support, in little windows to the side of the rad.. they are free-spinning...
 
EDIT: Looks like ryoken and I were posting at the same time...

I believe that for the blazers that the carriage bolts are always tack welded. You don't have to remove the radiator - you just put a socket w/ extensions down inside the channel of the core support. Kind of a PITA.

If you're not adding a body lift, you could probably get away with lifting the body up high enough that you won't have to replace the carriage bolts. But, if you get in there and find out the bolts are toast - then you're in a bit of a pickle.
 
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throw in 1/2 the time the ones under the front floor end up spinning in their cages and your cutting holes in the floor...

well, if you live anywhere with rust... :haha:
 
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