GMC Sierra 3500 HD (4X4) Question

[WhiteEagle]

Hi Folks,

My truck differential ratio, according to GMC towing documentation, is 3.73 with a maximum GCWR of 16,000 lbs. This is a gas engine, 6.0l Vortec. This is the extended cab, long box version.

I see from the same chart that if my differential ratio was 4.1 (some model came with this) then my maximum GCWR would be 20,500 lbs.

I weighed my truck and trailer at a CATS weigh scale, and it comes out close to 18,400 lbs (2,400 lbs over the GMC GCWR rating), and I still have about 400 lbs of gear to load in the trailer. These weights were without any water in the holding tanks!

I got a quote for changing the front and rear differentials to a 4.10 ratio, and it comes out to $4500.

So my question is this: If everything else is equal (brakes, suspension, etc) except for the front and rear differential ratios, will I be legal towing my trailer with this truck/trailer combination? Setting aside the legal question for a moment, will my truck/trailer be unsafe with a 3.73 ratio? According to the shop that quoted me the work, my engine will run about 200 RPM higher all the time (straight and level or uphill).

Side note: The CATS printout shows that my truck, with trailer hitched is 9,900 lbs (GVWR is 11,000 lbs) and the weight on the trailer wheels is 8,500 lbs. Both of these weights are below the axle ratings, so this isn't my burning issue. I'm more concerned about getting a $16,000 fine for being over weight. I hope this all makes sense....

[spock123]

Tell me how you are going to get a fine, are you commercial. Most people say it’s what’s on the yellow sticker on your door jam. But you aren’t ever going across a scale. Not a DOT scale

[WhiteEagle]

Originally Posted by spock123

Tell me how you are going to get a fine, are you commercial. Most people say it’s what’s on the yellow sticker on your door jam. But you aren’t ever going across a scale. Not a DOT scale

I'm not sure.... I read a forum post here a few weeks back about someone getting a $16,000 fine for being overweight. The details were a little sketchy to say the least.

[valleyduo]

To my knowledge there isn't a way to increase your factory sticker weights unless you would take it to a custom fab shop that can engineer it. I've also heard it can't be done at all. I'm not one to endorse pulling overweight, but I've never heard of an RVer getting weight fines. Most important things would be making sure everything looks good. If the back end of your truck is dragging, that would be pretty obvious.

[Kimber45]

don't know were you live, but in no state I have ever heard of does DOT have authority over a private non business vehicle. And im sure the civil police will weigh in, but in over 20 years of working with law enforcement I have never seen or heard of your average police officer responding to accidents have the ability to weigh a vehicle. The big question is what is the dry weight of your trailer? what is your truck rated to pull? what is the pin weight of your trailer? and what is the pay load of your truck? all those other numbers are for over thinkers.

[HangDiver]

OP is from Canada and up there LE can pull you over and check tow vehicle and trailer weights.

[KEliasz]

Also changing the axle ratio changes the torque of your vehicle NOT how much weight your rated for. To carry more weight you would need extra helper springs or much heavier springs. Dual axles for weight distribution etc... changing gear ratios would give you higher torque ie. More pulling power at lower speeds with a higher rpm and a lower top speed.

[KEliasz]

Also since I've done this before to my jeep for off road wheeling trips, 16 grand to swap gear ratios seems really high. It's basically a ring and pinion swap front and rear. I just blew and replaced my rear for less than 2 grand at a shop.

[valleyduo]

Originally Posted by KEliasz

Also since I've done this before to my jeep for off road wheeling trips, 16 grand to swap gear ratios seems really high. It's basically a ring and pinion swap front and rear. I just blew and replaced my rear for less than 2 grand at a shop.

$4500 was his gear swap quote. 16 grand is the fine he's trying to avoid.

[WhiteEagle]

Originally Posted by Kimber45

don't know were you live, but in no state I have ever heard of does DOT have authority over a private non business vehicle. And im sure the civil police will weigh in, but in over 20 years of working with law enforcement I have never seen or heard of your average police officer responding to accidents have the ability to weigh a vehicle. The big question is what is the dry weight of your trailer? what is your truck rated to pull? what is the pin weight of your trailer? and what is the pay load of your truck? all those other numbers are for over thinkers.

Hi Kimber,

Oddly enough, all my weights are below the sticker amounts. The GCWR rating is not on the vehicle sticker, and I had to do an exhaustive search to find it for my year, make and model. What's interesting is that according to GM, the only difference between my truck and one rated for the combined weight was the rear differential ratio (3.73 = 16,000 lbs, 4.10 = 20,500 lbs). I have heavy duty springs, shocks, air lift, etc. and my truck with trailer attached doesn't even rest on the springs (only the air lift bags). I have Kevlar tires which are overkill for this truck. The only concern I really have is whether law enforcement would give me the gears about the GCWR rating (again, not even posted on the truck door).

Maybe I'm over thinking this, but I do want to be safe....

[cmysstailights]

The only reason why the tow number are higher with the 4:11 gears is because it produces more torque. Same reason why a 3:08 silverdo tows less than 3:42. Do the gear swap and the truck will pull the bigger load easier. Your 3:73 setup will pull it just might take you longer to get up to speed.

[KEliasz]

I missed the $4500 part. That seems more reasonable. And like Kimber45 said, theres no where in the united states that I know of that would stop you for overweight unless your a registered commercial truck. I am in law enforcement for 15 years and I can honestly say I have NEVER done that or even thought about doing that

[swampdonkey772]

Theres only two times i know you will get weighed. If your in an accident and someone dies they weigh your rig and if your overweight your looking at vehicular manslaughter. Or if your three kind of guy to haul a 3 axel toy hauler fully loaded with a 3/4 ton truck. I frequent Pismo Beach Cali quiet often and CHP loves looking for those guys

[Kimber45]

as a side note I have the same issue with my ram 2500. Purchased it and a new 11k pound 5th wheel thinking the max tow was close to 16k. found out I have the other gears and my max tow is closer to 13k. the only difference is the gears. engine trans and suspension is all the same. I briefly looked into changing the gears and quickly changed my mind when I found out the cost and all ready awful gas mileage would get worse.

[swampdonkey772]

Ha. I'm in the same boat I bought the horse then my wife decided to change the cart. Now i have a 14mpg F250 that gets 8.5 towing

[cmysstailights]

Originally Posted by Kimber45

as a side note I have the same issue with my ram 2500. Purchased it and a new 11k pound 5th wheel thinking the max tow was close to 16k. found out I have the other gears and my max tow is closer to 13k. the only difference is the gears. engine trans and suspension is all the same. I briefly looked into changing the gears and quickly changed my mind when I found out the cost and all ready awful gas mileage would get worse.

How does ur setup pull. Only thing gears would help is getting up to speed and guessing little more ooomph on mountain pulls

[moose074]

You can go see look up the sae j 2807 standard it’s not a government standard not all vehicles manufacturers comply completely with this standard and most use a loaded flat bed trailer not a 5th wheel with the added wind catching 8x13 parachute

[Kimber45]

Originally Posted by cmysstailights

How does ur setup pull. Only thing gears would help is getting up to speed and guessing little more ooomph on mountain pulls

I have had zero issues. seems to handle it quiet well. 95 percent of my camping is within 30 minutes from home. longest trip was red river gorge last fall from Michigan and was very happy with it, even in the mountains.

[spock123]

Originally Posted by WhiteEagle

Hi Folks,

My truck differential ratio, according to GMC towing documentation, is 3.73 with a maximum GCWR of 16,000 lbs. This is a gas engine, 6.0l Vortec. This is the extended cab, long box version.

I see from the same chart that if my differential ratio was 4.1 (some model came with this) then my maximum GCWR would be 20,500 lbs.

I weighed my truck and trailer at a CATS weigh scale, and it comes out close to 18,400 lbs (2,400 lbs over the GMC GCWR rating), and I still have about 400 lbs of gear to load in the trailer. These weights were without any water in the holding tanks!

I got a quote for changing the front and rear differentials to a 4.10 ratio, and it comes out to $4500.

So my question is this: If everything else is equal (brakes, suspension, etc) except for the front and rear differential ratios, will I be legal towing my trailer with this truck/trailer combination? Setting aside the legal question for a moment, will my truck/trailer be unsafe with a 3.73 ratio? According to the shop that quoted me the work, my engine will run about 200 RPM higher all the time (straight and level or uphill).

Side note: The CATS printout shows that my truck, with trailer hitched is 9,900 lbs (GVWR is 11,000 lbs) and the weight on the trailer wheels is 8,500 lbs. Both of these weights are below the axle ratings, so this isn't my burning issue. I'm more concerned about getting a $16,000 fine for being over weight. I hope this all makes sense....

If I was as heavy as you are I would get a diesel dually to pull the camper. First and foremost you want camper and truck to be safe for your family. My SRW Silverado is rated to pull 16,700lbs loaded. I want to keep my SRW so if I should ever trade I’ll look for a camper that is 16,000lbs or less loaded. I don’t really want a dually besides my 2012 Silverado SRW is paid off and I don’t want another truck payment. If I was pulling that heavy camper I would first have safety for my family or you could buy a lighter camper. No US State DOT is going to stop you and weigh you. If it was me and I loved the camper I would get the dually, piece of mind. Your SRW will pull the camper fine and I have seen smaller trucks pulling bigger campers. It’s your camper and your truck, it’s your decision. I went to Alaska last year and I never saw any camper pulled over to get weighed, Alaska or Canada

[Brewhedd]

$4500 to change the gears in 2 diff's seems very high to me. Figuring parts at $1500, which is probably high, that leaves $3000 for labor. So it's going to take 30 hours to change gearing in both diff's?