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[77 K20 Trl Spec]

[updated:LAST EDITED ON Mar-27-03 AT 05:41 AM (CST)]I just bought a 77 K20 Trailering Special. I was wandering if anyone knew what is differant about this than other K20's? Also has a 454 from 73 passanger car what does that do for low end torque?

 

[DrMaserati]

Trailering package generally included things like heavy duty battery and alternator, power steering, trailer/camper wiring, and sometimes heavier radiator and trans cooler. Back then I don't believe it included a hitch.

 

[77 K20 Trl Spec]

I was told by the guy I bought it off of that it was basically a 1 ton. How could a person tell?

 

[DrMaserati]

That's kind of an old wive's tale. A one ton pickup of that era will have a GVW rating of at least 8600 pounds with single rear wheels, and 10,000 pounds with dual rear wheels. Both will have a full floating rear axle. A 3/4 ton will have a GVW rating of 8400 pounds or less. Making the jump from a 3/4 to a 1 ton will mean not just heavier springs, but heavier axles, bigger bearings and gears, bigger brakes, etc. It's much more than just springs. And a 1 ton will probably have TH400 transmission while a 3/4 will likely have a TH350. And putting a bigger engine in will not up the GVW rating.

If it's a K20, it's 3/4 ton and probably has a GVW rating of around 7200 pounds. With the camper package, it could be 8400 pounds. You'll find the GVW rating on a plate or sticker in one of the door openings, probably driver side. Think about it. GM is not going to take a 1 ton truck, which costs more to build, and call it a 3/4 ton and sell it for less. They're not that generous. Bottom line is, the guy lied to you. But the fact is, you still have a very good truck. As long as it meets your needs, it doesn't matter what it's rated at, unless you're just looking at the rating as a status symbol.

Back to your question about the engine in your first post. A passenger car engine generally won't have as much low end torque as one from a truck. It will probably have a higher horsepower rating. But the 454 in your truck will probably have more low end torque than the 400, which was the largest engine available in a K series at that time.

 

[77 K20 Trl Spec]

Thanks it has a gvw 8400 frt. 3700 rear 5560. The trailering special plate says 10000 gcwr. It has the larger brakes, a dana 44 front diff. and th400 tranny.

Larry H.

 

[DrMaserati]

What you have is probably what was called the Camper Special. The front and rear axle ratings will always total more than the GVW, but the GVW is still 8400. The Dana 44 is the standard front axle for a 3/4 ton, and the TH400 would be typical of a heavy duty application, such as the camper special or towing package.

The 10,000 rating you see is not the GVW rating, it is the Gross Combined Weigth Rating(GCWR) which means the weight of the pickup plus the towed load. But you would still not want to exceed the 8400 pounds on the pickup itself, including hitch weight. As an example, a pickup with a 10,000 pound GVW would typically have a GCWR of 13,500 to 16,000 pounds. If the total, loaded weight of your pickup is 6500 pounds, you will have 3500 pounds of towing capacity without exceeding the rated limit. However, while the bigger engine doesn't change the GVW, it WILL increase you GCWR, as would changing to a lower numerical axle ratio. A pickup with a 4.10 axle will have a higher GCWR than an identical truck with a 3.73 axle, even though their GVW ratings are the same.

What you have is the heaviest duty 3/4 ton pickup Chevy made at that time. And it's got a better engine than the original 400 small block, because it has better low end torque and doesn't have the 400's tendency to have overheating problems. Just make sure you have enough radiator to cool the larger engine in hot weather. You have an excellent truck.