The state of the K5 Blazer undergoing "Mods"

[Killain]

Since I have restored my 88 K5 just about from the ground up, (I looked for a longtime and only bought one from Texas) But I see so many threads on lifting the stock truck up 4,5 or 6", slapping on 38" or 42" tires ( mine had 38" tires when I bought it. But does anyone check the frames on these trucks ? I ask because the frame on these Blazers , and all 80's Gm trucks is about 5/32" in thickness. When I was rebuilding my truck i found a frame reinforcement kit sold by LCM trucks, and it adds to the steering box area, I thought it was a good idea, so I welded it onto my trucks frame and remounted the steering box. A simple job really. But I must say I'm amazed when I see these trucks lifted and flying off sand dunes or pounding through mud bogs, twisting turning and I have to admit, I'd be waiting for the damn thing to split in two. So does it make any difference the condition of the frames on these 30 year old trucks ? I waited till I found a Texas or Arizona truck to buy. I wouldn't trust a truck from the northeast or mid-america. GM didn't give much concern about either the quality or the strength of the steel they used in the manufacture of cars or truck in the eighties. It's not like the things were made out of SAE 440C or even 440A. I'm scared to even think what GM decided on for 1980's Auto/Truck manufacture. But when I see these beefed up engines pushing around 2.5 ton mud bogging 30 year old rigs, I don't want anyone hurt, but I have to wonder if anyone has ever been killed as a result of a broken chassis ?

 

[Bent77]

Oh I'm sure

Most of these you see here doing fun things, are fully caged. This significantly reinforces the frame

 

[ZooMad75]

I think a Blazer tub being one piece on top of the frame adds a certain amount of rigidity that a pickup truck chassis does not. Honestly, there are a TON of Blazers and Jimmy's running around on 4-8" of lift and 35-40" tires and not running any cage and not breaking frames. That does not include the frame around the steering box mounting as it's always been known as the weak link. But one needs to look at obvious areas like the rear shock mounts in the frame where the bolt is in single sheer and could come loose. I know I found mine loose recently. Leave it loose and the bolt will wallow the hole out in the frame and possibly crack it there. ORD sells a brace to put the mount bolt in double sheer and significantly reinforce that mount a lot.

Like anything else it really comes down to what YOUR intended use is. Mall crawler? Pavement Pounder? Trail ride? Rock Crawler? Pre-runner getting jumped? Camping rig? 33" tires or 40" tires? 4" lift or bigger? Leafs or Coil-overs? Depending on what you want to do with it should dictate what you need to do.

 

[Killain]

I think a Blazer tub being one piece on top of the frame adds a certain amount of rigidity that a pickup truck chassis does not. Honestly, there are a TON of Blazers and Jimmy's running around on 4-8" of lift and 35-40" tires and not running any cage and not breaking frames. That does not include the frame around the steering box mounting as it's always been known as the weak link. But one needs to look at obvious areas like the rear shock mounts in the frame where the bolt is in single sheer and could come loose. I know I found mine loose recently. Leave it loose and the bolt will wallow the hole out in the frame and possibly crack it there. ORD sells a brace to put the mount bolt in double sheer and significantly reinforce that mount a lot.

Like anything else it really comes down to what YOUR intended use is. Mall crawler? Pavement Pounder? Trail ride? Rock Crawler? Pre-runner getting jumped? Camping rig? 33" tires or 40" tires? 4" lift or bigger? Leafs or Coil-overs? Depending on what you want to do with it should dictate what you need to do.

Yeah I'm sure your right, it does matter what your doing and the gage of steel is strengthened by the forging or stamping process making it a 'C' channel. And I only mention it as I was kind of, not shocked but surprised by the thickness of the frame steel on my truck. And I'm pretty sure it is normal as this truck spent it's whole life in West Texas. And I didn't know that some of the folks here Cage the frames. As an frame example, a 10 wheel Peterbilts frame is about 10mm , drilled, crossmembers riveted and welded, and then heat tempered. Not hardened, but tempered so they can take a beating and not crack a million miles later. I tried to find the subject of the type and grade of steel used during the 60's, 70's and eighties but to no luck. Thank you for your reply.

 

[ZooMad75]

Yeah I'm sure your right, it does matter what your doing and the gage of steel is strengthened by the forging or stamping process making it a 'C' channel. And I only mention it as I was kind of, not shocked but surprised by the thickness of the frame steel on my truck. And I'm pretty sure it is normal as this truck spent it's whole life in West Texas. And I didn't know that some of the folks here Cage the frames. As a frame example, a 10 wheel Peterbilts frame is about 10mm , drilled, cross members riveted and welded, and then heat tempered. Not hardened, but tempered so they can take a beating and not crack a million miles later. I tried to find the subject of the type and grade of steel used during the '60s, '70s and eighties but to no luck. Thank you for your reply.

These are spaghetti frames with no reason to compare to over the road trucks. Keep this in mind. They built millions of trucks/Blazers/Suburbans from 1973 to 1991. If GM had a major problem with the frames being prone to failure it would be all over the place. They would be known for it. Hell, some Ralph Nader type probably would have made a big stink about it and brought up the idea of a Class Action lawsuit against GM. Nothing like that happened. As far as failures go, the squarebody trucks are known for the weak area for the steering box mount and the trucks having the fuel tanks exposed on the outside of the frame rails where some thought they were prone to fires. That one ended up with a Class action suit that Dateline NBC further adding fuel to the fire (pun totally intended) by using a detonation device to make the trucks explode in their testing to video and put up on TV since the dang trucks didn't explode like they wanted to for the video footage.

 

[Killain]

You have a good point there. If there even a hint of a problem, so many ambulance chasing lawyers would have been all over it to sue GM. And of course, the media likewise would have nursed for all was worth.

 

[diesel4me]

I'm sure many were injured or killed when the steering box tore loose from the frame,but most likely 90% of those that did that had been heavily modified with lift kits and huge tires,so that would let GM off the hook..

The frames on the newer GMT trucks are worse,the steering box area still cracks and or rots,and the boxed construction traps salt and moisture and rots them from the inside out..the tubular cross members usually rot thru first (the ones for the upper shock mounts and fuel tank straps)...you see many up here sagging badly enough to let the bed get pinched up against the cab and some break in half right after the cab's rear mounts ..

The frames thickness on square bodies does seem on the thin side even brand new,and after many years of road salt and flexing,they do eventually crack or rot thru...the steel used on square body frames seems to be skin hardened,once that top layer gets eaten away and flakes off,the remainder seems softer and rusts more rapidly,usually it crumbles into nuggets or flakes off in chunks like delaminated plywood..but they outlast the GMT boxed type frames..

I had a '56 Chevy pickup that had a frame at least 5/16" thick if not 3/8".and I owned it in the late 70's,early 80's.it was almost 25 years old by the time I had it and it still had no rot and looked like it was maybe 5 years old,just some surface rust,and it was never garaged and driven year round too...I think they used virgin steel in those days and it holds up much better..

 

[6872xtc]

Just to add about the steering box mounting point on the frame. Offroad Design makes a bolt-on brace which helps to spread the load even further and help avoid cracks. I saw a K5 crack the frame with only 33" tires after some decent wheeling with a front locker.

 

[diesel4me]

I had a '79 C-10 Bonanza 2wd that cracked the frame at the steering box with bone stock 235/75-15's..and the frame was rust free too!.
I had a certified welder stitch it back together,never bothered to reinforce it or add a brace,it didn't show any sign of further cracks as long as I owned it..
I also found some loose rivets in the cross member for the sway bar,I cut them off and put grade 8 bolts in their place..truck was only a straight six with a TH350 and didn't appear to have been worked very hard,if anything it was babied by the previous owner..truck was probably the cleanest and least rustiest one I ever had..