Finding Towing Capacity

rgeisler wrote:
Does anyone know how to find the actual towing capacity of a vehicle? Every source that I look at gives a different answer. I have a 2004
GMC Sierra 2500 HD 6.0 Liter, 5 speed automatic (I think), with Tow/Hauling button, Extended Cab/Long bed. When I look at the 2004 Towing Guide it gives several different ratings, I think based upon the Axle ratio, which I don't know, but it appears to be listed as 10,100 lbs. When I look up the VIN # at a site called Decodethis.com, it shows a maximum of 15,500 and a standard tow rating of 9900 lbs. I have no idea what the difference between the maximum and standard towing capacity is.

Nearly Identical truck to mine. You will have a 10.5" AAM full floating axle with 4.10 gears (RPO code GT5) and a 4L80E 4-speed transmission. That was the only gear and axle combo offered with the 6.0L/auto tranny.

Your GVWR will be 16,000 lbs, so yes, go weigh the truck and subtract that amount from 16K to find your max tow capacity. My truck is 2WD crew cab. Empty bed with a full tank and 2 adults it weighs 6,300 lbs. so I have about 9,700 lbs tow capacity.

The RAWR (rear axle weight rating) is 6,084 lbs, which is a limit of the OEM tires. These tires are rated at 3,042 lbs per tire @ 80 PSI. AAM rates the axle itself at 10,000 lbs, so that means your only limitation is the tires and/or the springs GM put on the rear.

If you're getting a ball-tow trailer be sure you ARE NOT using the OEM hitch receiver that came with the truck. These are a known poor design and there was much discussion about these years ago. Get a good Class V Receiver that has the receiver welded into the cross tube. When I towed with my OEM receiver I had a lot of porpoising and poor weight distribution even when using my WD hitch. After installing a Curt Magnum V receiver the towing experience was vastly improved.

The 6.0L engine needs to rev to make good power. There is a great torque band between 3200 RPM and 4400RPM where the engine pulls extremely well. I've towed all over central Illinois (yes very flat), southern Indiana, and made multiple trips to Bristol TN. You have to let it rev, but I've never felt outmatched by our 7,500 lbs TT.

Oh, one final thing, watch the exhaust manifold bolts. After making hard pulls the front and rear bolts on both sides tend to snap. You'll eventually develop an exhaust leak and will notice significantly reduced power. You can fix the problem by swapping in hardened bolts. I chose to install stainless steel shorty headers from Gibson and the kit came with new hardened bolts. I didn't take any measurements for power output pre or post installation, but it does seem the engine will rev a little quicker with the headers. That faster revving means I reach that magical 3200 RPM quicker so I'm hitting that torque curve faster.

I hope this info helps.

KJ