GVWR ? can someone explain how I figure out how much I can tow ?

Discussion in 'Towing & Trailer Tech' started by JTward1, Jan 3, 2013.

  1. JTward1

    JTward1 Rockstar 100 Posts

    SANY0092.jpg SANY0080.jpg I've posted the weight door sticker and a picture of the Class 2 under bumper squar hitch that is on the truck. The RPO codes say it came from the factory with a 5600 lbs GVWR. But I'm still a little fuzzy on how you determine you useful towing load. Thank you !
  2. mfleetwood

    mfleetwood Epic Member 5+ Years ROTM Winner 5000 Posts

    Use the link below:

    Enter your VIN number and then click on the "Equipment" tab...it will tell you what your towing cap is.


    - - - Updated - - -

    I went ahead and entered your VIN # and it appears your truck did not come from the factory with the tow package or tow hitch receiver, thus it is not rated/listed using your VIN nor RPO code. The top link below is the link to your truck info, so please double check to make sure the data is a match for your truck.

    If it's not listed there, someone else may be able to provide you an answer if they are familiar with your truck, you can call a dealership/GM, or post your question the "Ask GM...." thread (bottom link).


  3. Jamm3r

    Jamm3r Member 2 Years 100 Posts

    The various methods of arriving at a safe towing weight are controversial.

    The conservative school of thought says that you take the lower of:

    a) The rating of the hitch. There should be a sticker but sometimes they fall off. If what you have is truly a class 2 hitch then it's 3500 pounds, but most 2" receivers are class 3 or 4 hitches that carry more than that.

    b) The rating of the vehicle as provided by the manufacturer, minus the weight of any passengers and cargo in the truck. Trailer life publishes a summary here:


    There is also a searchable database here:


    The data only goes back to 1991 but I see ratings from 4000-7500 depending on engine and axle ratio with most of the common combinations being around 6000 pounds.

    A few people further derate the towing capacity by 10-20% for mountainous areas.

    There is another school of thought that holds that during this particular period in history automakers were underrating the towing capacity of their trucks as a marketing strategy to sell powertrain upgrades. ::shrug::

    One thing is for sure, and that's that you don't want to exceed the GAWR for the rear axle, so if you're doing any heavy towing you should take a trip over the scales and check the weight on the rear axle.
  4. JTward1

    JTward1 Rockstar 100 Posts

    That's a pretty good tool. Mine has a 8' bed though. But most of all the rest is correct.

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    That's a neat tool, And I have wondered why the original owner ordered RPO code : C5G + GVWR of 5.600 Lbs. springs ? The sub frame towing frame is darn near identical to the Factory one. Or least it looks identical to the one in the brochure. I'd like to use it to haul cars with a modest trailer, one car trailer. But I'd sure feel more comfortable knowing what parameters I'm dealing with. I'd really like to know what 1990 RPO code : C5G The brochure isn't all that helpful as it have a lot of options and charts but I'm not astute to sort them out and be able to understand what it means equipment wise.

    I plan on replacing the rear springs and install a posi-Traction differential. I wonder what size or weight springs should I install to replace the pair I now have ? Any advice you can lend will be greatly appricated. I plan on hauling a single car auto transport trailer. Thank you !

    I do have a Pennsylvania "Class 2 sticker" for the truck, but I don't want to use it just yet because it is permenat and once on the windsheild I get charged a higher toll no matter if I'm towing or empty. Oh, on the top of the ball and on the side of the hitch where it attaches to the sub frame, 6,000 lbs.
    Last edited: Jan 4, 2013
  5. mfleetwood

    mfleetwood Epic Member 5+ Years ROTM Winner 5000 Posts

    Yeah..I saw the longer bed in your album and I picked the 8' because of that, but for some reason it keeps on displaying the shorter one.

    C5G is your gross vehicle weight, which is 5,600 lbs. You will be able to find that code and others using this link...http://www.rpocodes.com/GM-RPO-codes/gmrpocodesAthroughF.html

    I agree with you in fully knowing what your limits are.

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    I just realized that your thread was not the towing section of the forum, thus moved it. This will help in gathering more opinions/feedback.
  6. JTward1

    JTward1 Rockstar 100 Posts

    Thank you !

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    I bought a 2" square hitch with a 3.5" drop and on top of the 2" ball is stamped 6000 so I'm assuming that is the load limit, and it has a 600 pound tongue limit ? ( and it was the only one 'Made In America). They may sell Chinese junk, but it don't mean I gotta buy it. One of the things that has me a little stymied is the truck came from the factory with all the equiped RPO in the glove box. And it has a GU6 RPO and that states it's a 5600 pound springs, (I assuming, I don't know but thats why I'm here, to learn) But the truck has what looks identical and is in the 1990 Chevrolet light truck brochure towing section calls a " Weight-Distributing Platform hitch Receiver" and it is attached to the truck frame by 6 -3/4"nut-bolts & lock washers on it, 3= to a side. and it looks like it was (Again I'm assuming) dealer installed. I found a complete listing of all RPO codes affecting 1990 Chevy /GMC RPO codes. I looked each one up and wrote them down on a 8"x11" pad.

    The thing that doesn't make any sense to me why would someone buy the truck and add the GU6 option (Heavy rear springs) only to go back to the dealership to have this weight dis.platform hitch receiver ( that's what it's called in the 1990 sale brochure I found on the auction place). Install and yet skip on the RPO for a Limited slip differential ? That's like installing a 7.4 liter engine in a car and then putting on a 2bbl carburetor ? But I'm new to the trailering crowd, so I am interested in all your opinions. My only goal is to hook up a aluminum or steel 1 car towing trailer. Not really for business but just to help out here and there. I am a real old time covert and love only Chevy/GMC trucks.

    And old trucks and Corvette have a lot in common: It's really hard to find one that's not beat to S*&^ and still runs on it's own power, with out $50.000 in power modifications, none of which your invested in owning.. belong to a Corvette club and pretty often someone somewhere needs to have a car towed and not have to pay $75.00 hook up fee and then a $1.00 a mile transport fee. These towing companies are just like the old westerns with cattle rustlers
  7. jake's silverado

    jake's silverado Epic Member 5+ Years 500 Posts

    So what We can know 100% is the most your truck can weigh is 5600#. So fill it full of fuel and put you and whomever rides with you and weigh the truck. This will give you what you have left for tongue weight. as well be mind full of your rear axle limit of 3404 lbs. the VIN decode stated the curb weight is 3700 so you have about 1900 Lbs left for payload (that includes you and the passenger) so lets take off about 300 and that leaves about 1600lbs. Looking on line the oldest truck towing rating I could find was for a 1998 with 3,73 rear end was 7000 lbs. I guess you don`t have the owners manual. I will keep looking to see if I can find more info.

    If you know what rear end you have that would help.

    99'HEARTBEAT MODERATOR Staff Member 5+ Years ROTM Winner 1000 Posts Platinum Contributor

    The RPO Code GU6, that you've posted in your reply, is not (Heavy Duty Springs)........RPO Code GU6.....is 3.42 REAR AXLE GEAR RATIO.....that your Truck came with from the Factory.
    Last edited: Jan 4, 2013
  9. JTward1

    JTward1 Rockstar 100 Posts

    Well I have the owners manual as well as the Chevy dealership light truck brochure and if I'm reading it right it says the truck can haul 10.500 pounds. The truck has a 305 V8 700R4 & 3:42 standard read. if I take the 4000 pounds away that leaves 6.500 pounds correct ? The rear end is a 3:42 ration and that is what is listed in the 10.500 pond payload. Thank you for any advice.
    Last edited: Jan 6, 2013
  10. jake's silverado

    jake's silverado Epic Member 5+ Years 500 Posts

    10500 lbs would mean you probably need some sort of HD trailering PKG on the truck. with the 3.42 that was in my 2009 that had the HD trail PKG only gave me 9600 lbs max trailer. So I think you rally need the RPO codes to see what if any trailering PKGs are on your truck.

    Your math "if I take the 4000 pounds away that leaves 6.500 pounds correct ?" is incorrect. What you need from your Owners Manual is the the GCWR (Gross Combined Weight Rating) which is the the total (actual) weight of the Truck and the trailer combined. So if it says for your truck it is 14,000# take away what your truck weighs (4000) that leaves 10,000#. (using your numbers) I'm not saying that your truck can't pull 10,500# but you still need to know what trailering packages your truck came equipped with, once you know then start looking at trailers and the tongue weights that will keep within the limits of the truck.

    Once you know what you have then the trailers info is key. When the tongue weights are posted you need to ask if that includes propane/batteries... FYI my 31' travel trailer has a posted tongue weight of 785# but with propane, batteries and a weeks worth of camping supplies wife and dog the tongue is 960# and GCWR was 15,000#. this is 1000# below my GCWR. The trailers GVWR 8000# and the shipped tongue weight (what the trailer manufacturer posted in the brochure) is at 785#. So the actual weights for the tongue could be a lot higher. As well the actual weight of your truck may be higher based on added options accumulation of dirt...
    So not a bad idea to weigh the truck with you and a full tank of fuel for an idea.

    Hope this helps a bit.

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