Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

Ok I'm working on a Theory here on frame cracked at steering box

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Grim-Reaper, Jun 13, 2001.

  1. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

    Joined:
    Feb 17, 2000
    Posts:
    7,385
    Likes Received:
    0
    Location:
    Atlanta
    Ok I\'m working on a Theory here on frame cracked at steering box

    Well I noticed several people here recently cracked the frame around the steering box. I noticed that all the trucks were late 80's and it got me to thinking. A couple of these trucks even had the ORD brace on it. Both my 70's trucks have over 300k on them and my 75 has been beat on hard over the years. When I got it the front springs were broken so it has not had it easy. No cracks at the box even afer all the misstreatment it went though.
    Here is my Theory. I think that the newer trucks have a thinner frame that may even be a different temper. There have been some obvious changes in the frame over the years. 2 big ones is when the rear foot well was added in 78 and then frame horn changes in 81. Well our trucks are pigs and I think GM put them on diet. Some obvious changes are in the 70's the inner fenders were steel, 80's are plastic. Some changes in the front sheetmetal and hood hinge. again the 70's trucks are heavier in these areas. I think these changes go deeper. I thing they may have even used thinner steel for the body and frame. We also get a wide varrity of dfferent topper weights.
    What I need is to find out what a mid 70's (after 75 probaly 78-79 would be the best for the weight since they are the closest design when they went to the half top) and a late 80's truck, with roughly the same options listed, curb weight is. I think we are going to find about 400lb difference if my gestimation is correct. I guess this because the spring rate for the stock late 80's springs is so much lower than the 70's trucks.
    Next thing I need is have a few people with micrometers and calipers is to measure the frame thickness at a couple points. I only have a micometer so I can't get a good measurement up next to the steering box. I figure a measurment on the frame below the box and above both axles and behind both bumpers should get us some good data. Again I'm looking for Mid 70's and late 80's.
    I think were are going to find the newer trucks have a thinner frame.
    Last thing is for those that have broken a frame at the box is what year your truck is. Mods like crossover steering and tire size.
    Just a thought and I figured you folks might be just as interested and help explain the rash of cracked frames.



    It's not my damn planet monkey boy!
    Grim-Reaper
     
  2. CK5

    CK5 In my underwear Administrator Premium Member GMOTM Winner Author

    Joined:
    May 19, 1999
    Posts:
    21,623
    Likes Received:
    701
    Location:
    CO
    Re: Ok I\'m working on a Theory here on frame cracked at steering box

    Not sure on the frame thickness, would be cool to find out, I know starting in 89 I think the body is galvanized and seams a little thicker and the inner fender on my 90 is steel. The real weigh savings on the newer models comes from the 700r4 and the alum NP241 and the 10 bolts.
    I haven't had any problems untill flexing the 37" swamps with no cross over.

    Steve

    Bandwidth FREE ZONE

    Mall-Running poseur 4x4 with curb-feelers
     
  3. muddin4fun

    muddin4fun 3/4 ton status

    Joined:
    Feb 19, 2001
    Posts:
    5,644
    Likes Received:
    0
    Location:
    N Texas
    Re: Ok I\'m working on a Theory here on frame cracked at steering box

    I've got a '79, and I know for a fact the sheet metal is thicker....just don't know how much thicker. My '86 truck was parked outside behind my hubby's '79 (the one he used to have) and a big hail storm happened and the '86 got some hail damage, but the '79 didn't get a single dent. My hubby works at napa so he might have some of those tools, so I'll try to get some measurements. I'm interested in what you find cause I think that in the 80's GM was experimenting with lighter material, but didn't have the experiance yet in what you can and can't get away with so the 80's trucks have some weak links that the 70's and before trucks didn't have. I can't get a curb weight cause there's no weigh stations anywhere near me, but I'll try and get some of the measurements.

    <font color=purple>Have you hugged your K5 today?</font color=purple>
     
  4. Boss

    Boss 1/2 ton status Author

    Joined:
    Feb 17, 2000
    Posts:
    2,550
    Likes Received:
    0
    Location:
    Maryland
    Re: Ok I\'m working on a Theory here on frame cracked at steering box

    Well, I still have my 75' and the 89', so I can take some measurements...actually, I have the one ton axles under the 89' so, some may not be accurate like stock. I'll check the frame thickness.
    One thing for sure, is the inner fender wheel well is definately steel in the 89'.
    But you're right, I think the 75' sheet metal is thicker than the 89', atleast it seems so. But the 89' is galvanized therefore not prone to rust as much (even though mine was rusted out in 5 different areas big enough to stick my hand through. [​IMG]
    Anyhow, that's an interesting theory (or Theories) you got there, we'll see how it pans out.
    Boss

    <A target="_blank" HREF=http://www.boss.coloradok5.com>http://www.boss.coloradok5.com</A>
     
  5. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

    Joined:
    Feb 17, 2000
    Posts:
    7,385
    Likes Received:
    0
    Location:
    Atlanta
    Re: Ok I\'m working on a Theory here on frame cracked at steering box

    Steel on the inner fenders on 89 and 90. Hmmm Keith has a 86 with plastic. This may have been a thing that was different between plants or GM found the plastic fenders were not holding up and went back to steel.

    It's not my damn planet monkey boy!
    Grim-Reaper
     
  6. CK5

    CK5 In my underwear Administrator Premium Member GMOTM Winner Author

    Joined:
    May 19, 1999
    Posts:
    21,623
    Likes Received:
    701
    Location:
    CO
    Re: Ok I\'m working on a Theory here on frame cracked at steering box

    I'll bet the 69-75 frames would be thicker to help with flex due to the full top, I know they had additional support in the floors.

    Steve

    Bandwidth FREE ZONE

    Mall-Running poseur 4x4 with curb-feelers
     
  7. Boss

    Boss 1/2 ton status Author

    Joined:
    Feb 17, 2000
    Posts:
    2,550
    Likes Received:
    0
    Location:
    Maryland
    Re: Ok I\'m working on a Theory here on frame cracked at steering box

    Grim,
    Maybe 86' is the first/last year for plastic?? Not sure, but I know that the 87's came with steel also...well, atleast the one I've seen...I never really looked/payed attention to one that was an 86' or older (still in the 80's)...so, who knows.
    Boss

    <A target="_blank" HREF=http://www.boss.coloradok5.com>http://www.boss.coloradok5.com</A>
     
  8. kpanza

    kpanza 1/2 ton status

    Joined:
    Dec 8, 2000
    Posts:
    1,579
    Likes Received:
    0
    Location:
    Lake Forest, Orange County, California
    Re: Ok I\'m working on a Theory here on frame cracked at steering box

    My '87 has steel inner fenders! Never seen one with plastic myself yet...but I think you're theory has a good chance of being proven right!! I don't have any of those measuring tools, but I can tell you that I DID have the steering brace in when it cracked. I have been running 35s for 5 years on it, and the last year it has had the ARB locker up front, no crossover steering, RockRod...it sees regular trail use, especially rocks!

    Keith

    Keith
     
  9. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

    Joined:
    Feb 17, 2000
    Posts:
    7,385
    Likes Received:
    0
    Location:
    Atlanta
    Re: Ok I\'m working on a Theory here on frame cracked at steering box

    Well we know the hood changed in 81. Did the 86 get dents in the roof as well? That would confirm the tub being thinner. Do you recall if it had plastic inner front fenders? The K5 Keith has is a 86 as well. I was surprised to see they were plastic that or I'm halucinating and didn't see what I thought I saw. I know a lot of 80s GM cars had plastic inners.

    It's not my damn planet monkey boy!
    Grim-Reaper
     
  10. fr8train

    fr8train 1/2 ton status

    Joined:
    Aug 2, 2000
    Posts:
    1,712
    Likes Received:
    0
    Location:
    Maryland
    Re: Ok I\'m working on a Theory here on frame cracked at steering box

    My 88 has steel inner fenders. I am going ot check that frame out withthe calipers and a mic.
     
  11. bigblue

    bigblue 1/2 ton status

    Joined:
    Dec 6, 2000
    Posts:
    658
    Likes Received:
    0
    Location:
    southern california
    Re: Ok I\'m working on a Theory here on frame cracked at steering box

    My inner fenders are metal ... 87
     
  12. LittlePig

    LittlePig 1/2 ton status

    Joined:
    Aug 9, 2000
    Posts:
    299
    Likes Received:
    0
    Location:
    East Texas
    Re: Ok I\'m working on a Theory here on frame cracked at steering box

    If the change happened, I bet it was after 82. I seem to recall reading something about the early 80s trucks being the same as the 70s machines, with a change around 83. Could it be that the lighter truck showed up at the same time as the 700R4? And I wonder if this extends to the Army Blazers too, which had 3/4 ton springs. They should be stronger everywhere else too, right? They better be. I don't wanna have to try transplanting a diesel into a 78 Blazer to get the truck I want.

    Email: xiaozhu@my-deja.com
    ICQ: 84108805
     
  13. 79Jimmy

    79Jimmy 1/2 ton status

    Joined:
    May 10, 2000
    Posts:
    214
    Likes Received:
    0
    Location:
    Richmond BC, Canada
    Re: Ok I\'m working on a Theory here on frame cracked at steering box

    Well I just put a Mitutoyo Digital mic on about 6 different places along my 79 Jimmy frame. Average reading was 0.154 inches or approx. 5/32" Measurments ranged from 0.151" to 0.157" As far as the plastic inners, I know JC Whitney sells some aftermarket ones so thats were I think they're from. Every truck I've seen had steel inner fenders.
    Hope that helps

    James



    79jimmy@home.com
     
  14. 84_Chevy_K10

    84_Chevy_K10 Banned

    Joined:
    May 30, 2001
    Posts:
    17,669
    Likes Received:
    0
    Location:
    IL, USA
    Re: Ok I\'m working on a Theory here on frame cracked at steering box

    The Army Blazers also had dual 10 bolts with 3.08 gears and NP 208s.

    Now the Army trucks, on the other hand, had Dana 60/14 bolt and usually NP 205s. They usually had 4.56 gears, all of them are locked in the back, some locked up front too.

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles
     
  15. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

    Joined:
    Jul 23, 2000
    Posts:
    36,175
    Likes Received:
    1,385
    Location:
    E-town baby!
    Re: Ok I\'m working on a Theory here on frame cracked at steering box

    I don't know how accurate the figures are but in the specs area it lists curb weight for each year as well as options.

    1990 supposedly weighs in a 4839 lbs, 1979 with a cast iron T-case weighs in at 4371 lbs. This would seem to run counter to the theory. If the tub was thinner in 90 and the frame too you would think it would be lighter than the 79...

    My 81 Jimmy has no steering brace, has been rolled, jumped and generally wheeled without mercy, its even been rear ended badly and my frame at the steering box is not cracked. Its had 35" tires minimum for the last 4 years and 33's for 2 or 3 years prior to that. Every time I go wheeling my steering wheel is in the same relative position as before the trip.

    Rene

    <font color=green>Dyslexics of the world...UNTIE!</font color=green>
     
  16. wayne

    wayne 3/4 ton status

    Joined:
    Feb 1, 2001
    Posts:
    6,178
    Likes Received:
    0
    Location:
    Carlisle, Pa
    Re: Ok I\'m working on a Theory here on frame cracked at steering box

    I have seen mid 80's 2 wheel drive trucks that the frames cracked on. When I lived in Ga I was looking into buying a truck in Forest Park and the guy said the steering box was broke. When I got there the box was not broke, the frame had a hole where the box was supposed to be. The 73 truck I bought has 3 times the miles that the 81 did and is solid at the box.

    <A target="_blank" HREF=http://jamonline.homestead.com/fromthegroundupK54x4/89Jimmy.html>http://jamonline.homestead.com/fromthegroundupK54x4/89Jimmy.html</A>
    <font color=blue>Happy Trails<font color=blue>
    <font color=blue>Wayne<font color=blue>
     
  17. Executioner

    Executioner 1/2 ton status

    Joined:
    Feb 22, 2000
    Posts:
    1,530
    Likes Received:
    0
    Location:
    Temp. Ft. Walton Beach Fl. home=Tucson, Az.
    Re: Ok I\'m working on a Theory here on frame cracked at steering box

    Cool theory, we'll see how it pans out !
    Do you think, battery acid, rust, and corrosin in that area may weaken the frame ?
    Or any other Enviromental chemicals ?
     
  18. titanic

    titanic 1/2 ton status

    Joined:
    Mar 27, 2000
    Posts:
    498
    Likes Received:
    0
    Location:
    north alabama(huntsville)
    Re: Ok I\'m working on a Theory here on frame cracked at steering box

    I do think weight has plenty to do with some frames cracking but I believe most are due to incorrect stops on the turning knuckles. Most cracked frames I have seen are on 4-6 " lifted trucks where the stops on the knuckles were not adjusted to stop the front tires from turning sharper than the steering box would allow. The pitman,box, draglink are all stronger than the frame after repeated flexing the weight of the front on the box itself. It the truck has a locker or owner likes to rockcrawl-more chances of seeing those cracks Steve
     
  19. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,980
    Likes Received:
    189
    Location:
    Roy WA
    Re: Ok I\'m working on a Theory here on frame cracked at steering box

    I wouldn't doubt it for GM to lighten the frames up for economy purposes. Case in point, the 78-88 Cultass, Monte carlo, etc., have 'perimeter frames' which are basically nonexistent in the middle, with boxed on either end. I thought they were unibodies at first. Anyways, they also used plastic inner fenders.

    I really doubt that stock, any of the trucks had plastic inner fenders. If GM didn't learn in how many years? 15? that the Gov Lock wasn't very strong, and that the tailgates cracked, and that MAYBE galvanized metal was a good idea, I don't think a 1 year plastic only fender would be plausible. It would take GM much longer to acknowledge, much less fix, a problem like that. Besides, Gm would have done research on that, if it was bad enough to have been discovered in one year, it never would have been produced. (I know there are always exceptions, but generally here...)

    One other explanation for frame cracking MIGHT be that GM strenthened the frame around the engine mounts in the 80's, and that may add extra strain on the steering area. FWIW, on a non-abused truck, with sane sized tires (lol) I have never seen a broken frame.

    To be fair with the thicker frame argument, my dads '74 K20 was an Alaska Pipeline truck, and both front frame rails (about 8 inches) were actually ripped off and welded back on during its life. If thats not rough service, I can't imagine what is. Nonetheless, it does not have a cracked frame. Never heard of this as a problem on the Army Blazers either, but I haven't been around them enough to know what kind of problems they may have had in that area. But they also only used 31" tires, not 33's, 35's, 44's, what have you. If I had my calipers here, I'd measure the frame on the truck right now. just one more thing to add to my tool box lol.

    Dorian
    My tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
    No anti-theft measures on your truck? No pity when its stolen
     
  20. 45acp

    45acp 1/2 ton status

    Joined:
    Jan 3, 2001
    Posts:
    695
    Likes Received:
    0
    Location:
    Tucson, Arizona
    Re: Ok I\'m working on a Theory here on frame cracked at steering box

    Grim, My body is off and frame is bare so its easy to measure the thickness from end to end. The average (.155") thickness is pretty consistant from end to end. This is for a 1983 GMC Jimmy and the inner fender wells are steel.

    Bill Hughes
     

Share This Page