70 C30 dually combined towing capacity GCWR? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

jarrodblake · 03-19-2018, 03:21 AM

I am trying to calculate the combined towing capacity for my 70 C30. The truck has a maximum gvw rating of 14,000lbs. The truck is a dovetail flatbed truck. the bed is 13 feet with a 4 foot dove tail. My plan is to make the dove tail removible and add a hidden GooseNeck hitch. I would like to be able to pull a GooseNeck camper. Or even a flatbed GooseNeck trailer with a small camper and a vehicle on it. However I do not know what size trailer I can pull or how to calculate it.

I know modification do not increase factory towing capacity ratings. But I am in the middle of converting it to disk brakes all around. hydro boost and air suspension. The truck already has a trailer brake controller but I plan on upgrading it. I also have a nv4500 for it.

I have read a few threads but they are all dead ends. I can not find anything on google it looks like all chevys until like 89 did not have a GCWR.

Richard2112 · 03-19-2018, 10:17 AM

I am sort of interested in this also as I too have a 70 C30. But regardless of it's rating, (I have been told that the rear tire load rating is key), I consider axle wrap to be a primary consideration, leaf spring capacity, axle cap, shock absorbed "down travel" and brake capacity/function to be relevant considerations. An anti-sway or anti-roll bar would also be a consideration as mine didn't come with one.

I am running HD shocks, a traction kit, leaf over-load springs and a 14 bolt w/3.73's, 32 inch tires (I think load cap is 2600 each), 3.50 brake rear shoes in 13 inch drums and front discs. Recently rebuilt/installed an NV4500 (added mechanical speedo gears from sm465). Have yet to add anti-sway bar and am considering additional set of air shocks to adjust height.

My concerns are what size trailer I can control. Wet or dry pavement.

**kwmech** · 03-19-2018, 10:37 AM

Finishing up my 69 flatbed C30 14k rated. I'm not worried about anything in the future I may tow. I'm setting up the flatbed with a goose plate and a 5th plate along with a class IV receiver on the apron. Big block, T400 with a gear vendor Dana 70 HD rear with 4.10s and a detroit. 235/85r-16 10 ply tires. I figure I can pull anywhere up to a 15k trailer with electric brakes

03-19-2018, 03:21 AM	#1
jarrodblake Registered User Join Date: Sep 2017 Location: Patriot IN Posts: 163	70 C30 dually combined towing capacity GCWR? I am trying to calculate the combined towing capacity for my 70 C30. The truck has a maximum gvw rating of 14,000lbs. The truck is a dovetail flatbed truck. the bed is 13 feet with a 4 foot dove tail. My plan is to make the dove tail removible and add a hidden GooseNeck hitch. I would like to be able to pull a GooseNeck camper. Or even a flatbed GooseNeck trailer with a small camper and a vehicle on it. However I do not know what size trailer I can pull or how to calculate it. I know modification do not increase factory towing capacity ratings. But I am in the middle of converting it to disk brakes all around. hydro boost and air suspension. The truck already has a trailer brake controller but I plan on upgrading it. I also have a nv4500 for it. I have read a few threads but they are all dead ends. I can not find anything on google it looks like all chevys until like 89 did not have a GCWR.

03-19-2018, 10:17 AM	#2
Richard2112 Registered User Join Date: Jul 2014 Location: South East Ohio Posts: 644	Re: 70 C30 dually combined towing capacity GCWR? I am sort of interested in this also as I too have a 70 C30. But regardless of it's rating, (I have been told that the rear tire load rating is key), I consider axle wrap to be a primary consideration, leaf spring capacity, axle cap, shock absorbed "down travel" and brake capacity/function to be relevant considerations. An anti-sway or anti-roll bar would also be a consideration as mine didn't come with one. I am running HD shocks, a traction kit, leaf over-load springs and a 14 bolt w/3.73's, 32 inch tires (I think load cap is 2600 each), 3.50 brake rear shoes in 13 inch drums and front discs. Recently rebuilt/installed an NV4500 (added mechanical speedo gears from sm465). Have yet to add anti-sway bar and am considering additional set of air shocks to adjust height. My concerns are what size trailer I can control. Wet or dry pavement.

03-19-2018, 10:37 AM	#3
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,650	Re: 70 C30 dually combined towing capacity GCWR? Finishing up my 69 flatbed C30 14k rated. I'm not worried about anything in the future I may tow. I'm setting up the flatbed with a goose plate and a 5th plate along with a class IV receiver on the apron. Big block, T400 with a gear vendor Dana 70 HD rear with 4.10s and a detroit. 235/85r-16 10 ply tires. I figure I can pull anywhere up to a 15k trailer with electric brakes



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