Question for the Pros

Discussion in 'Tech Discussion' started by Shagydelic86, Oct 30, 2018.

  1. Shagydelic86

    Shagydelic86 Junior Member

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    Good evening folks, I'm new here and also new to the square body world. Its been a dream of mine to own an '80s square body dually and it seems my chance has arrived. Though I have a few questions to ask before I make the jump.

    The ad listed the truck as a 1984 Chevy 3/4T Dually with the 454/400. It seems there is no a lot of information out there, but I was under the impression that all dually's are 1T trucks. It's reported that there has been no conversion done on the truck and that it's all factory. I was informed that they had a dealer verify the VIN and it indeed came back as a 3/4T (I'm waiting to get the VIN tonight do complete some more research).

    My question is, what are some identifying markers that I would notice on a C20 with a conversion vs a C30. Any help would be greatly appreciated! And look forward to joining the family!

    Thanks,
    RHP
     
  2. bucket

    bucket Super Moderator Staff Member

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    Very first thing, look for wheel adapters. GM did not use them.

    There also were no 3/4ton duallies. So all you can figure out is what's been done to the truck, rather than whether or not it's original.
     
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  3. Shagydelic86

    Shagydelic86 Junior Member

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    Thanks so much! I was perplexed as to there being factory 3/4T duallies.
     
  4. Charlie

    Charlie Full Access Member

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    :welcome:
     
  5. K201979

    K201979 Full Access Member

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    :welcome: Are u gonna go for it?
     
  6. Craig 85

    Craig 85 Supporting Member Supporting Member

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    Here's the easy way to see if it's a true C20 or C30. Look if the shocks are inside the frame or outside. 1 tons have the shocks inside the frame and they are reversed from 1/2 and 3/4 tons. The R/R shock on a 1 ton is on the back of the axle. Although my truck is a SRW K30 the set up is the same as a C30 dually.

    IMG_1188.JPG
     
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  7. Shagydelic86

    Shagydelic86 Junior Member

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    Gonna see how the walk around goes.

    Thanks for the info! Thats great. I do have the VIN and it's decoding to be a C20. It's also showing the 350 engine, though I'm being told it's for sure the 454. Guess time will tell.
     
  8. Shagydelic86

    Shagydelic86 Junior Member

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    I'll let you all be the judge. Any thoughts? Questions I need to be sure to ask about it? What is a "must look at" for these trucks. Thanks for you input.

    RHP

    Chevy Truck 2.jpg Chevy Truck 3.jpg Chevy Truck 4.jpg Chevy Truck 5.jpg Chevy Truck.jpg
     
  9. K201979

    K201979 Full Access Member

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    Judging by some of the threads ive seen here, there aint nothin that can't be fixed. Just depends how far ur willin to go. Looks like a solid, straight truck but it does sound like its had lots work done, just gotta figure out if it was for the better or worse:D i say if everything normal checks out and nothin feels funny or sounds weird, go for it! Just fix it if it breaks. Still cheeper( and cooler:D) than a payment on a new one!
     
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  10. SDJunkMan

    SDJunkMan Full Access Member

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    It may have had a cab swap at some time, which might explain the title/VIN saying that it is a C20.
     
  11. Shagydelic86

    Shagydelic86 Junior Member

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    @Craig 85 Been looking for pics of chassis. Question for you to confirm what you're saying. The C30's will have shocks mounted inside the frame vs C20's shocks will be mounted on the outside of the frame? Also, you mention that they are "reversed" on the 1/2 and 3/4T trucks. Is that mentioning that on a C20, the L/R shock will be mounted behind the axle, being that is opposite of the C30?

    Thanks for your help!

    RHP
     
  12. CSFJ

    CSFJ ----------------- Supporting Member

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    The 3/4 ton crew cabs were built with a one ton frame also. You would need to find out if that means they also ran the one ton shock absorbrer arrangement. On the plus side, if this truck truly started life as a 3/4, then it would at least be a legit conversion putting the one ton suspension onto the existing one tone frame that the crew cab came with. The other option I believe was mentiioned above, that it could have been cab swapped at some point.
     
  13. 75gmck25

    75gmck25 Full Access Member

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    I will have to take a look again at my 8200 lb GVW K25, but I believe the shocks are mounted on the outside of the frame, but they are both on the same side of the axle (not staggered). Mine has the camper special package, so maybe that was a variation in the suspension.

    Bruce
     
  14. Craig 85

    Craig 85 Supporting Member Supporting Member

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    @Shagydelic86 When I wrote my post , I forgot about the C20 3+3's (crew cab). I had an '80 in the mid 90's and it does have the same rear suspension as a 1 ton. Springs are mounted closer to the frame which require the shocks to be mounted on the inside of the frame. I don't know the reason from GM, but 1-ton rear shocks are the exact opposite of 1/2 & 3/4 tons. On 1-tons the R/R shock is on the back side of the axle and the L/R is on the front side.

    Here's a current picture of my rear axle and the position of the shocks. The second picture is of a C20 standard cab, not the 3+3. You can see the difference between the 2 set ups.

    Here's a link to a prior discussion. https://www.gmsquarebody.com/threads/3-4-ton-vs-1ton.5964/

    IMG_1665.JPG
    [​IMG]
     
  15. Craig 85

    Craig 85 Supporting Member Supporting Member

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    The other thing I just noticed is the bed is from the 70's as it exposed gas caps and doesn't have gas doors. I'm not sure when the actual change was made, but I know my '79 1/2 ton had fuel doors and so did my '80 C20 3+3. One other detail to look for is hydro boost on the brakes. 1 tons had them.
     

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