Can my truck tow this?

[ksnider74]

So like any other new person that's bought a travel trailer I probably have put the cart before the horse. So ultimately the question is can I tow this...
I have a 2019 GMC Sierra Elevation DC 4x4 with the tow package and the L84 engine and a 3.23 gear ratio. The limitations are

9400lb Towing capacity
7000lb gvwr
15000 GCWR
3800 GAWR RR
940 tongue weight

The trailer I bought was a 2020 Venture Sport Trek 322VRL with
1010 dry hitch weight
7580 dry weight
8820 loaded weight

So I know that the owners manual for the truck gives specs and limitations and states any trailer must have a WDH and then shows 50%? So can I tow thing or what?

Thank you all in advance and will appreciate any feedback.

[8_1_Van]

If you don't have 8 lug wheels then fagetaboutit. I busted a 6 lug 1/2 ton axle @70mph on I-95 in SC in 1986 and have only used 3/4-1 ton 8 lug trucks since then for towing TTs.

[Grit_dog]

^ lol

[Jayco-noslide]

What the heck is that about "making up numbers and frozen children"?

[blt2ski]

valhalla360 wrote:

JRscooby wrote:
The ring and pinion in the rearend not only change the speed/power of rotation, they also change the direction. And I'm not a engineer, but I have rebuilt rearends that have different ratios moving the same loads. A higher speed ratio puts a lot more side force on the bearings. (And most of the "Bang! truck won't go" failures happen in reverse. Turning backward, the shape of teeth adds to the force"

But we are still back to...if you are within ratings, you shouldn't expect "bang! truck won't go".

They already addressed durability when setting the ratings.

Like ALL things great and small. No matter the tow rig too, you need to know WHAT the specs are for said ratings.just because you think you are under ratings, you may very well be way the heck over the ratings.
Examples.
Minimum gradability in first gear is 12%.if on a 13% grade, you may or may not be able to start, or if you hit said grade mid trip up a road, you may stall out.
Max frontal area for a given weight is 60 sq ft for smaller rigs, 80 sq ft for larger rigs. If maxed out weight Wise, but over the frontal area, you may not you may or may not make it to freeway speed, or hold the minimum speed required up a 5% freeway grade, over heat engine, trans, differential.
Minimum speed on said 5% freeway grade is 35 or 40 mph depending on gvw of the rig. Your minimum personal spec may be 50. You would consider said spec too low. You need more HP to go 50 mph, or lower the weight of trailer or frontal area, or make it more aerodynamic to meet your min speed spec.
I've had rigs under ratings, that di way worst than those OVER ratings. Depends on how the drivetrain is speced.

Marty

[JRscooby]

valhalla360 wrote:

But we are still back to...if you are within ratings, you shouldn't expect "bang! truck won't go".

They already addressed durability when setting the ratings.

You are right, a RVer is very unlikely to get over ratings far enough to hear the bang. But that does not change the fact that higher speed rear ends put more side force in the rear end. That friction must be overcome.

[valhalla360]

JRscooby wrote:
The ring and pinion in the rearend not only change the speed/power of rotation, they also change the direction. And I'm not a engineer, but I have rebuilt rearends that have different ratios moving the same loads. A higher speed ratio puts a lot more side force on the bearings. (And most of the "Bang! truck won't go" failures happen in reverse. Turning backward, the shape of teeth adds to the force"

But we are still back to...if you are within ratings, you shouldn't expect "bang! truck won't go".

They already addressed durability when setting the ratings.

[Grit_dog]

^LOL, and for the small small % of people who prioritize climbing a 30% grade at max gcvw or more from a dead stop with a 1/2 ton, AND drive 15-20mph UNDER the posted speed limit in some places, the new 1/2 ton gearing isn’t optimal or needed for you.
But mfgs don’t typically mass produce things that aren’t popular or wanted by the majority, so there’s that.
For the rest of us, we can have a machine that not only tows very well, but cruises very comfortably with low rpms at high speeds.

[blt2ski]

Grit dog wrote:
Gents, I don't think anyone is arguing that lower final drives multiply torque more and generally are better for towing.
What I am saying, is, now, with more powerful engines and more gears (super deep first, 5-7 more underdrive ratios and still a couple OD gears) we can now have our cake and eat it too compared to times of yore.

Grit,
WHile I agree with ALL that you are saying. Some of us do not drive over 60-65 mph.....at all! As such, these taller RA ratio's while nice from an MPG at freeway speeds....some of us never will literally use or need said DOD gear, UNLESS, we can get a lower RA, say a 3.73 or 4.10 to have a decent rpm at 60-62.

But as noted, one needs an overall ratio of 24-1, with 400 lb ft of torque, to move 20K lbs up a 30% grade. How you get there, does not matter, you can do a 4-1 axle, 6-1 trans. or a 3-1 axle, with an 8-1 in trans. Both will do an equal job. The 4-1 with a .75 OD, will net you a 3-1 final drive, if the 3-1 RA is running in direct, same 3-1 final ratio.

No right or wrong way to look at this issue, only what is BEST for whos reading my 02!

Marty

[MFL]

Grit dog wrote:
Gents, I don't think anyone is arguing that lower final drives multiply torque more and generally are better for towing.
What I am saying, is, now, with more powerful engines and more gears (super deep first, 5-7 more underdrive ratios and still a couple OD gears) we can now have our cake and eat it too compared to times of yore.

Yup, lots of bickering, lack of understanding of modern day drive trains. Getting the best of everything, low end torque for takeoff when towing, taller gears with double overdrive for mileage, when not towing, and the ability to lock out gears to lessen up/down shifts, while running in the middle gears, or uphill/downhill.

Haven't heard from the OP in many pages, but I think he figured it out, early on, that his modern day/new truck will work.

Jerry

[Grit_dog]

Gents, I don't think anyone is arguing that lower final drives multiply torque more and generally are better for towing.
What I am saying, is, now, with more powerful engines and more gears (super deep first, 5-7 more underdrive ratios and still a couple OD gears) we can now have our cake and eat it too compared to times of yore.

[twodownzero]

While downshifting may give you the same overall gear reduction as a lower gear ratio in the axles, it puts a lot more stress on the transmission to do that. Auto transmissions aren't getting much physically larger. The clutch plates still have similar surface area to what they had 30 years ago. Even if they were 100% bigger than they once were, all the heat from that gear reduction has to be dissipated over that surface area. I don't drive automatics, but if I did, I'd want to give them the best chance they could get at doing that job.

The driveshaft actually sees the most load/torque when taking off from a dead stop (torque peak of engine + max gear reduction). A driveshaft really doesn't care about what is downstream of it; its strength is a rating based on torque, of course over which there is a significant engineering factor, probably 2-3:1. Today's trucks have driveshafts that are MUCH stronger than trucks from 30 years ago. Just go to the parts store or catalog and look at the U-joints these days; they're very beefy.

I may be one to typically prefer overkill when it comes to this stuff, but when the weather is bad, the mountains are steep, etc., it certainly pays off to have more truck rather than barely enough. That doesn't mean everyone needs a 1 ton DRW to pull a pop up, but when trailers get in the 8k pound+ range, it's time for a heavy duty pickup, especially when lengths are long as well.

[JRscooby]

Grit dog wrote:
^ This is correct theory scooby. But in general, the same overall gear reduction or overdrive ratio is achieved, so the engine sees the same load for equal parameters.
Generally. Now one would have to calculate "minor losses". IE greater friction from greater stress in the 3rd member due to a smaller ring gear vs less friction/stress in the transmission at the same time.
Stress on the driveshaft is real. But that's easy and cheap to beef up (as a mfg).

The ring and pinion in the rearend not only change the speed/power of rotation, they also change the direction. And I'm not a engineer, but I have rebuilt rearends that have different ratios moving the same loads. A higher speed ratio puts a lot more side force on the bearings. (And most of the "Bang! truck won't go" failures happen in reverse. Turning backward, the shape of teeth adds to the force"
And yes, it is not hard to beef up a driveshaft, as a mfg. Larger tube or thicker walls. Beef up motor mounts? No issue. (Remember when GM had the recall to add a cable from engine to frame?) Make frame stiffer to reduce flex under power? Sure. But all that adds weight. And it takes fuel to move the weight. I'm sure they have worked out all the numbers, account for percentage of time the vehicle will be working at max, and are sure everything will last at least as long as the warranty.

[valhalla360]

Terryallan wrote:

What you are ignoring. Is the fact that with a lower gears the tow rating are increased. So what may be pushing the limits for a truck with a 3.15 rear, is well with in the limits of a truck with a 3.73 rear. The truck is rated on how it is equipped. Higher gears equals lower tow rating. Lower gears equal higher tow rating. It is simple physics. Lower gears deliver more power to the ground at lower speeds, and most important of all. From a stop. You only got one low gear / starting gear to choose from. and there is a HUGE difference in a 3.15, and a 3.73. Your TV will let you feel the difference by raising up on one side when you start off, if your gear is too high. Upper gears / 4th 5th 6th, mean nothing if first gear can't get you started.

No, I'm not ignoring it. If you are trying to tow a 9k trailer with an 8k rated truck...dropping the rear end to a lower gear to get 10k rating does change things (mostly limited to hard mountain runs...not so much on sea level flat land). But no one ever suggested it was a good idea to tow over the trucks limits and expect good performance towing...the presumption is always that both trucks are within ratings and everything except the rear end is identical.

Yes, gear ratios make a difference...with 10speed transmissions though, you can pick the ratio you want to get the performance you want...it's overall gear ratios that matter for performance and for most practical purposes, they will be the same.

As far as 0-60 acceleration...generally, most RVers don't do jack rabbit starts but....

If you look at the new 10 speed transmissions, 1st gear is far deeper than the old 4 speed transmissions. Example: 1990 Ford 1st gear was 2.84:1. 2019 1st gear 4.69:1...that will negate the issue you describe with needing more torque to start a truck while towing.

[valhalla360]

JRscooby wrote:

Is the engine the only part of the vehicle that takes a strain? Yes, the more verity of ratios in trans is better for engine. Just pulling numbers off the donkey, I don't know what would be real on a RV. If it takes 1000ft/lbs of torque at the wheel to move the load, with 4:1 rearend, the driveshaft is only carrying 250ft/lbs plus friction in rearend. But if the ratio is 2:1 the driveshaft must carry 500ft/lbs plus more friction in the rearend. And that increase in force is also applied to frame, motor mounts and more.

Again, assuming you are within the tow ratings...driveshaft and everything else is designed to handle the strains in both trucks.

Of course, you example is extreme...I've never seen a 2:1 rear end...certainly not put up against a 4:1 rear end in any kind of realistic scenario. With more normal comparative rear ends say 3.55 to 3.73...the extra strain and more importantly, internal friction changes are not that big to where it's likely to have a measurable impact on efficiency or parts failure.

Friction will be different in the rear end but you will get an opposite effect on friction in the transmission...Net effect is likely in the range of a rounding error.