K20 vs. K30 Difference

[SquareRoot]

I don't see any K30 pieces (frame, differentials) in the pics supplies in the post. Another poster had replied that it was the HD K20 and that is not is what is in the pics supplied. I have a '79 K20 now that is a 10 bolt front and 14FF rear and have never seen a K20 with a front Dana 60. Dodge, Ford, IHC and even Jeep do this on 3/4 tons but I've never seen one from the General. Ford even had a few F-150's with 5 lug Dana 60's on both ends. Here we go down the rabbit hole...

Yup...gone!

 

[Strick]

Yup...gone!

I couldn't remember who had the "rabbit-hole" background. I know now! Thanks.

HS

 

[Blue Ox]

I don't see any K30 pieces (frame, differentials) in the pics supplies in the post. Another poster had replied that it was the HD K20 and that is not is what is in the pics supplied. I have a '79 K20 now that is a 10 bolt front and 14FF rear and have never seen a K20 with a front Dana 60. Dodge, Ford, IHC and even Jeep do this on 3/4 tons but I've never seen one from the General. Ford even had a few F-150's with 5 lug Dana 60's on both ends. Here we go down the rabbit hole...

I think you misread my post. There are two K20s after 1980. Std and HD (C6P). Full float rears are not definitive of a C6P heavy duty package after '80. The 14 bolt SF became standard on 20s with 11" drums for the std and 13" on the HD. Unless the buyer optioned it the FF was in K30 territory at that point. Also, I didn't mean to imply that D60 fronts were on K20s, although I wasn't clear.

 

[Strick]

I think you misread my post. There are two K20s after 1980. Std and HD (C6P). Full float rears are not definitive of a C6P heavy duty package after '80. The 14 bolt SF became standard on 20s with 11" drums for the std and 13" on the HD. Unless the buyer optioned it the FF was in K30 territory at that point. Also, I didn't mean to imply that D60 fronts were on K20s, although I wasn't clear.

No problem at all. Someone else posted that the truck in the pic was HD but it's the opposite. That's what I pointed out.

HS

 

[Blue Ox]

No problem at all. Someone else posted that the truck in the pic was HD but it's the opposite. That's what I pointed out.

HS

The current pics look like a K20 chassis. I couldn't tell if it's an HD or not without measuring the frame thickness or the brakes. Maybe the spring pack count would tell you. Otherwise I have to go by the info he's giving us. If the VIN says it's a J engine it's an HD chassis. Assuming everything is original.

 

[Strick]

The current pics look like a K20 chassis. I couldn't tell if it's an HD or not without measuring the frame thickness or the brakes. Maybe the spring pack count would tell you. Otherwise I have to go by the info he's giving us. If the VIN says it's a J engine it's an HD chassis. Assuming everything is original.

Those pics supplied were a short frame, a 14SF rear and 10 bolt front. Another post came in and said it was an HD. Square root replied back as well as me to this post.

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[Frankenchevy]

Axles can always be swapped. You can tell the frame isn’t a k30 frame by the rear leaf hangers and outboard shocks. The shocks are inside the frame rails on a k30.

 

[Blue Ox]

Those pics supplied were a short frame, a 14SF rear and 10 bolt front. Another post came in and said it was an HD. Square root replied back as well as me to this post.

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Okay. I'm utterly lost here as to where this is going. It seems like people are confusing a 20HD with a 30 or don't understand that there were two versions of the 20.

 

[bucket]

Okay. I'm utterly lost here as to where this is going. It seems like people are confusing a 20HD with a 30 or don't understand that there were two versions of the 20.

The way I'm reading it, you and Strick are both correct. You are correct that for the time frame, it could be the heavier version of the 3/4 ton. Strick is correct that it basically shares none of the heavier suspension and brake components with a 1 ton truck, like that other guy had suggested.

 

[Strick]

The way I'm reading it, you and Strick are both correct. You are correct that for the time frame, it could be the heavier version of the 3/4 ton. Strick is correct that it basically shares none of the heavier suspension and brake components with a 1 ton truck, like that other guy had suggested.

Thanks. No more rabbit-hole!

HS

 

[Dano500]

What you likely purchased is a 3/4 ton heavy duty. It would have the big brakes and it is rated as 8600 GVW. I have an 85 3/4 heavy duty that is all stock except for a 3 in. Body lift I put on it. The door label shows it has the 8600 GVW rating too. What this means to you is much of the drivetrain is 1ton without the dually wheels.

So, did we determine if there is such a thing as the K20 HD? I have the 14SF and 13" brakes and 8 leaf pack. I have the G brake code for 8001 to 9000. According to what I can find a 350 mated to the th400 is the heavier towing package and comes with 4.10s...

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Yes, I know the u-bolts *were upside down and has since been corrected. lol

Up to a point....

I own a 1985 3/4 ton and it was built with the C6P 8600 GVW package. So it was heavy duty emissions with a "J" code diesel engine with a 10" GM front and a 14 bolt semi floater rear with 13" drums and the heavier frame modulus that went with a heavy 3/4 ton truck as opposed to a "light" 3/4 ton.

There's a frame spec thread somewhere in the library that covers it.

There's a split in the 3/4 ton trucks from the 1973 to 1980 truck vs the '81 & up trucks where the components got lighter. A D60 front and 14 bolt full-float rear was 1 ton territory at that point.

Is it only the J code, or diesels that were heavy k20s? I ask because mine is a 350.

 

[Blue Ox]

So, did we determine if there is such a thing as the K20 HD? I have the 14SF and 13" brakes and 8 leaf pack. I have the G brake code for 8001 to 9000. According to what I can find a 350 mated to the th400 is the heavier towing package and comes with 4.10s...

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Yes, I know the u-bolts *were upside down and has since been corrected. lol

Is it only the J code, or diesels that were heavy k20s? I ask because mine is a 350.

Any 20 series truck with a C6P RPO and GVW over 8500 lbs would be considered Heavy Duty. 13" drums are a giveaway.

 

[vr1967]

Another thing to remember is that the k30 frame has the shock mounted inside the frame instead of outside.

 

[Dano500]

@Blue Ox i have no idea if it has code C6P. It’s not original glove box and I don’t know what the frame modulus is to check that. I was just wondering if there was another way to tell, like the larger brakes you mentioned. Is the HD payload 2800?

Another thing to remember is that the k30 frame has the shock mounted inside the frame instead of outside.

This thread was referencing a k20 frame with heavier components like the larger brakes and frame modulus for a heavier GVW.

 

[Blue Ox]

@Blue Ox i have no idea if it has code C6P. It’s not original glove box and I don’t know what the frame modulus is to check that. I was just wondering if there was another way to tell, like the larger brakes you mentioned. Is the HD payload 2800?


This thread was referencing a k20 frame with heavier components like the larger brakes and frame modulus for a heavier GVW.

Payload would vary a lot depending on the truck's options. GVW is the only way I can think of to determine if it's HD or not. The 8500 lb threshold is a gov't thing, not GM. It applies to emissions probably more than anything else. So your engine VIN may be a clue.

You could try looking at the GM Heritage center for the literature on your year truck. It will have the full listing of options, engines etc. that make up the various packages.