2015 Pentastar V6 Towing [SUPERCHARGER SUCCESS!]

[RamInfo]

Putting that much mod money into a 5yr old truck is hard to justify from both a towing functionality and sentimentality standpoints. Mod up the truck and it will no longer really be the truck her father selected and enjoyed.

Keep the truck as is, make it your wife’s daily driver, then tow the camper with whatever you were using before OR sell that vehicle and find a nice late-model 1500 w/5.7 and 3.92s, or a 2500 with 6.4 and 3.73s. The latter will have you ready for the bigger trailer you’ll eventually want. And you won’t have to deal with issues from an aftermarket blower setup.

Best,
DG

 

[engineering]

I have the very same truck configuration and I'm planning on pulling 22' TT at 3800 lbs. dry and roughly at 4500 lbs. fully loaded. On paper this total weight shouldn't be a problem for this truck since I know people pulling similar trailers with SUVs or small pickup trucks.
Is the 4600 lbs. weight you stated a dry weight or fully loaded total weight?
Thanks.

I estimate that it is about 4900 fully loaded. It has not been on a scale yet but that is pretty close.
The weight is part of the equation, the horrible coefficient of drag (wind resistance) adds a LOT to the power requirements. A short utility trailer of the exact same weight is much easier to tow.

It does? It's more like the engine
Isn't far enough into the torque band to upshift. When your not towing, use the Tow/Haul and see how far it up shifts at 80 mph

I would not bet my life on it, but it never shifts into 7th even when gong 65mph on a down grade. I have not really experimented that much with this either and a lot of the time, I have the transmission on manual as well. The fastest I have pulled the trailer is 65. No way I would attempt 80mph even if I had the power to do it.

The engine will hold those rpms all day long, the bigger concern is overheating if there too much load and lugging and engine at too low of rpms. Most people overlook wind as part of the load, they focus on the actual weight. I've towed an enclosed car hauler(3K lbs actual) in high enough wind gusts it would make my EcoD downshift, under normal conditions I don't know it's back there.
Gassers like to brag about their HP and torque numbers but get gun shy when it come to using it. If you want to be able to tow in the 2K rpm range: your running the wrong fuel, missing a turbo and have spark plugs.

There is no question that wind resistance is a BIG factor which is not overlooked at all. I am just going by the combination of weight (rolling resistance) and coefficient of drag (wind resistance) and on hills we also get gravity increasing the drag. I have no expectation to avoid all downshifting or maintain 2k RPM in every situation. After I trip from LA to Dallas and back - which is very mild hills, I was disappointed with how it handled very slight grades. There were a lot of stretches where 60mph pushed it into 3rd gear which is about 4300 RPM @ 60mph. For brief stretches, maybe that is ok but seems excessive for long periods.
A trip we took to Death Valley was really dramatic going through the mountains, we were going very slow and still something like 4k+ RPM for a long time.

Putting that much mod money into a 5yr old truck is hard to justify from both a towing functionality and sentimentality standpoints. Mod up the truck and it will no longer really be the truck her father selected and enjoyed.

Keep the truck as is, make it your wife’s daily driver, then tow the camper with whatever you were using before OR sell that vehicle and find a nice late-model 1500 w/5.7 and 3.92s, or a 250p with 6.4 and 3.73s. The latter will have you ready for the bigger trailer you’ll eventually want. And you won’t have to deal with issues from an aftermarket blower setup.

Best,
DG

I totally agree. Trust me when I say that I am struggling to inject logic into this effort. As far as I my wife is concerned, if she cannot see it - it is not there. A supercharger is out of sight. Even an over-the-top full engine swap would be out of sight [which I would never consider].
She loves her daily driver and does not want to get rid of it. Her father definitely chose this truck based on economics and only wanted it for the occasional trip to the lumber yard to get a few pieces for his woodworking projects. He never thought it would be used for cross country towing. Kind of a crazy situation trying to put a square peg in a round hole. If this was solely up to me, I would have sold the truck immediately and purchased a more task appropriate model that does not need any mods.

 

[Fishstickz]

Putting that much mod money into a 5yr old truck is hard to justify from both a towing functionality and sentimentality standpoints. Mod up the truck and it will no longer really be the truck her father selected and enjoyed.

Keep the truck as is, make it your wife’s daily driver, then tow the camper with whatever you were using before OR sell that vehicle and find a nice late-model 1500 w/5.7 and 3.92s, or a 250p with 6.4 and 3.73s. The latter will have you ready for the bigger trailer you’ll eventually want. And you won’t have to deal with issues from an aftermarket blower setup.

Best,
DG

I kinda agree here. Thats a great setup for a daily driver or for long travels when you don’t take your camper. I would personally would spend that money on a better-equipped tow rig

With all the money spent on upgrades you would have to make, you could probably put down a hefty down payment on a truck built for towing heavier from the factory. I see gas prices going through the roof in the near future, and if thats the case you might enjoy having that V6-3.21 combo


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[392DevilDog]

These trucks are designed to run at peak horsepower and torque all day long.

They have to rev. That is were the power is

Manually put it in 3rd gear and let her sing. That is were she needs to be to even get close to the power.

• 305 @ 6,400 rpm Horsepower
• 269 @ 4,175 rpm Torque

You need to be here to notice the power. You have to rev that girl. She loves it.

 

[engineering]

I kinda agree here. Thats a great setup for a daily driver or for long travels when you don’t take your camper. I would personally would spend that money on a better-equipped tow rig

With all the money spent on upgrades you would have to make, you could probably put down a hefty down payment on a truck built for towing heavier from the factory. I see gas prices going through the roof in the near future, and if thats the case you might enjoy having that V6-3.21 combo

It is a great daily driven eco-truck with excellent MPG. Pushing it into towing duty is counter intuitive.

These trucks are designed to run at peak horsepower and torque all day long.

They have to rev. That is were the power is

Manually put it in 3rd gear and let her sing. That is were she needs to be to even get close to the power.

• 305 @ 6,400 rpm Horsepower
• 269 @ 4,175 rpm Torque

You need to be here to notice the power. You have to rev that girl. She loves it.

3rd gear at peak torque is about 60mph which is a reasonable speed. The question is does this put me into a 60k mile engine rebuild? 80k if I am lucky? Maybe it makes very little difference as long as I keep the fluids and filters fresh? Hard to say.
What about the constant shifting of the transmission? On a regular trip the number of gear changes is kinda crazy as the truck tries to stay in a workable power band. Even if the engine lives a long life, the transmission may go early because it shifts 6x more than when it is not loaded.

A supercharger increases the pressure load on the engine but keeps it slower and the transmission is shifting a LOT less. I am not sure if that is a net gain in longevity/reliability or not. Maybe it is all the same and I should just run it at 4200 RPM all day long as you suggest.

I am an engineer (not automotive) and all of my machines predictably wear faster when they move faster. How much faster is the question and it is complicated to answer.

 

[392DevilDog]

You trying to run at low RPMS. And lugging that engine. That will cause the issue.

REV THE ENGINE. IT HAS TO IN ORDER TO MAKE POWER.

and that is why i said to select 3rd gear. So the transmission will not shift as much. You do mot want the transmission shifting all thr time. Rev thr engine

Here in Pennsylvania when I am going up and down the grades I put my 392 Hemi 2500 into 2nd gear. Throttle control instead of transmission input.

Hell. Select 2nd gear run it til you get to the flat and then select 3rd.

Did you see peak horsepower is at 6400 RPM. YOU NEED TO SPIN THAT ENGINE

 

[Quyonmob]

I would look at going deeper than 3.92 for that weight just for the torque multiplication. Don’t fear the gear, the pentastar is happy to rev.

FWIW, my 17 crew 3.6 with 3.21 sounds like it tows the exact same as yours, and I generally have a lighter load.

The load of the wind is the killer, my truck happily tows up grades on slow roads (50-55mph). It hates long grades on fast highways (65+mph).

We seem to have this odd fear of constant higher rpm in vehicles, but anybody from the boat world has run 300+HP motors at a static 4500+rpm for hours on end.

 

[engineering]

You trying to run at low RPMS. And lugging that engine. That will cause the issue.

REV THE ENGINE. IT HAS TO IN ORDER TO MAKE POWER.

Did you see peak horsepower is at 6400 RPM. YOU NEED TO SPIN THAT ENGINE

The peak HP and the best RPM for a reasonable life are NOT the same number. There is a reason there are 2 overdrive gears and the engineers are pushing for the lowest possible RPM at a given speed. Part of it is directly related to fuel economy and part of it is longevity/reliability.

I would look at going deeper than 3.92 for that weight just for the torque multiplication. Don’t fear the gear, the pentastar is happy to rev.

FWIW, my 17 crew 3.6 with 3.21 sounds like it tows the exact same as yours, and I generally have a lighter load.

The load of the wind is the killer, my truck happily tows up grades on slow roads (50-55mph). It hates long grades on fast highways (65+mph).

We seem to have this odd fear of constant higher rpm in vehicles, but anybody from the boat world has run 300+HP motors at a static 4500+rpm for hours on end.

True but boats never (very rarely) get the time that road vehicles get. They tend to get pounded hard for a few hours here and there and then sit in the slip or trailer for weeks and months.

I am a pilot and the piston planes I have owned/flown can make 300hp at very low RPM around 2200-2500. This is the ultimate need for reliability and the goal is always to run at lowest possible RPM for longest engine life even if that means using turbos to increase manifold pressure to make that happen.

 

[ramffml]

I don't need or expect any increase in the ratings of the truck - I just want it to do better when legally fully loaded.





Here is what I see.
With 3.21 rear in 6th gear which is 1:1 gives 60mph at 2000 RPM with the tires I am running.
Lets pretend the engine is delivering a round number of 200ft/lbs of torque at this RPM (accuracy is not important at this point)
That will deliver about 320 ft/lbs to the contact patch of the tire.


With a 3.92 rear in 6th gear which is 1:1 gives 60mph at 2500 RPM with the tires I am running.
That will deliver about 391 ft/lbs to the contact patch of the tire but at 500 RPM higher (not bad at all).

When the 'Tow Mode' is active, the overdrive gears are locked out and the truck never goes past 6th. The gear change from 3.21 to 3.92 puts 22% more torque on the ground at the expense of 500 RPM (which the engine delivers a little more torque as well).
This will reduce the need for the transmission to downshift to 5th, staying in 6th on the modest grades that are now requiring a shift to 5th. The steeper grades go from 6th to 5th to 4th where perhaps the gear change can keep it in 5th.
I think the rear gear change has a real benefit on the highway - not just a low speed thing.

There is no more torque on the ground, if you're going the same speed at the same RPM. Yes you may get more torque out of a specific gear number, but don't forget the gear ratio is what matters.

If two otherwise identical trucks have different rear ends, but are driving the same speed at the same RPM, then by definition they HAVE to be putting down the same torque. The 3.92 will be in (say) 7th, whereas the 3.21 has to do it in 6th, but who cares what numerical gear you are in? The transmission will pick the gear you need to get your RPMs up.

Here is the best way to think of it.


3.21 B C D E F G H
3.92 A B C D E F G

Note how the first gear of 3.92 (A) doesn't have a match. But first gear of 3.21 = second gear of 3.92 (Both have a gear ratio = B). Last gear of 3.92 = 7th gear of 3.21 (G), and then 3.21 has an additional gear (H) after that.

That's all the gear ratios are doing for you. The 3.92 is giving you a bottom gear and taking away one from the top end, but when you're in the middle of the gears, towing on the highway, both trucks have the exact same gear ratios to choose from (D - G), even though the numerical gear number might be different it's irrelevant.

In short, you're not getting anymore torque on the highway whatsoever.

(Actually it's a little bit different in the lower gears, they're not exact matches, but close enough. The higher gears are almost 100% identical)

 

[Quyonmob]

True but boats never (very rarely) get the time that road vehicles get. They tend to get pounded hard for a few hours here and there and then sit in the slip or trailer for weeks and months.

I’m talking commercial boats.

 

[392DevilDog]

The peak HP and the best RPM for a reasonable life are NOT the same number. There is a reason there are 2 overdrive gears and the engineers are pushing for the lowest possible RPM at a given speed. Part of it is directly related to fuel economy and part of it is longevity/reliability.

I am not an engineer. So I will not argue with you.

The engine needs to rev to make power. There are 2 overdrive gears because people have made fuel efficiency more important than perfor.ing work

The engines are made to work. That is why you will see different ratings for the same engine across the Mopar brands.

You want to not rev an engine get a diesel
You want to keep the truck and have it perform the towing task. Rev the engine.

Why do you think tow/ Haul mode changes shift points and locks out 8th gear. Because the truck needs to rev

Trucks used to be built to work...they are now sedans and drive by people who want MPG.

I have a jeep Cherokee also with the 9spd transmission. Put it in sport mode at the 3.2l v6 in it surprises me with power. Put it in auto and it lags and tries to stay in the high gears for MPG.

I use sport mode a lot.

To each their own

 

[Quyonmob]

There is no more torque on the ground, if you're going the same speed at the same RPM. Yes you may get more torque out of a specific gear number, but don't forget the gear ratio is what matters.

If two otherwise identical trucks have different rear ends, but are driving the same speed at the same RPM, then by definition they HAVE to be putting down the same torque. The 3.92 will be in (say) 7th, whereas the 3.21 has to do it in 6th, but who cares what numerical gear you are in? The transmission will pick the gear you need to get your RPMs up.

Here is the best way to think of it.


3.21 B C D E F G H
3.92 A B C D E F G

Note how the first gear of 3.92 (A) doesn't have a match. But first gear of 3.21 = second gear of 3.92 (Both have a gear ratio = B). Last gear of 3.92 = 7th gear of 3.21 (G), and then 3.21 has an additional gear (H) after that.

That's all the gear ratios are doing for you. The 3.92 is giving you a bottom gear and taking away one from the top end, but when you're in the middle of the gears, towing on the highway, both trucks have the exact same gear ratios to choose from (D - G), even though the numerical gear number might be different it's irrelevant.

In short, you're not getting anymore torque on the highway whatsoever.

(Actually it's a little bit different in the lower gears, they're not exact matches, but close enough. The higher gears are almost 100% identical)

It’s where the torque multiplication occurs, taking the load off the trans. Hence why the exact same truck is rated for 2500lbs more towing with 3.92 than with 3.21.

The 8hp45 is barely an 8spd with 3.21, as 8th is nearly useless.

 

[dhay13]

That motor is going to rev. Different truck and engine but I had a 2007 1500 with the 4.7 and 3.92s and towed my 14x7 enclosed trailer (weighed about 3500lbs loaded) and at about 65 MPH on the highway I was in 3rd gear the whole time and turning about 3500 RPM. This was a trip from Pittsburgh to Indianapolis so all flat. The truck just didn't have the power to push that trailer through the wind. I think it stayed in 3rd gear the whole 4 hour trip. Either way, expect that engine to rev higher even on the highway at speed. A flat trailer doesn't strain it as much because it is easier to get through the wind.

3.92s will help on hills. Yes you can downshift to achieve the same RPM but heat is a transmissions biggest enemy and constant shifting will build heat.

 

[engineering]

There is no more torque on the ground, if you're going the same speed at the same RPM. Yes you may get more torque out of a specific gear number, but don't forget the gear ratio is what matters.

This is starting to smell like a supercharger.


Thanks for the details.

Yes you can downshift to achieve the same RPM but heat is a transmissions biggest enemy and constant shifting will build heat.

Yeah, I am certainly concerned about the non-stop shifting.

 

[NewBlackDak]

That motor is going to rev. Different truck and engine but I had a 2007 1500 with the 4.7 and 3.92s and towed my 14x7 enclosed trailer (weighed about 3500lbs loaded) and at about 65 MPH on the highway I was in 3rd gear the whole time and turning about 3500 RPM. This was a trip from Pittsburgh to Indianapolis so all flat. The truck just didn't have the power to push that trailer through the wind. I think it stayed in 3rd gear the whole 4 hour trip. Either way, expect that engine to rev higher even on the highway at speed. A flat trailer doesn't strain it as much because it is easier to get through the wind.

3.92s will help on hills. Yes you can downshift to achieve the same RPM but heat is a transmissions biggest enemy and constant shifting will build heat.

Anyone else remember towing with a small block before overdrive transmissions in trucks?


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[Quyonmob]

Anyone else remember towing with a small block before overdrive transmissions in trucks?


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Yessir. Cross your fingers and pray your way to the top in 2nd while staring at the temp gauge, or hit the 4way hazard lights and ride the shoulder in first.

 

[dhay13]

Anyone else remember towing with a small block before overdrive transmissions in trucks?


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Yep. Back in the late 80's early 90's I had a 1979 GMC Sierra 1500 with a mildly built 350 with 3.73's. Towed my 1969 Chevelle on an 18' Owens Classic open trailer back and forth to local drag strips.

 

[2003F350]

To make power, modern gas engines need to spin. I'm STILL trying to make my wife understand that - she and her dad are both used to the old days where big blocks made max torque at around 1800 RPM and max horsepower at 4500 RPM, with a redline around 5500-6000.

Modern gas engines, regardless of size now, need to spin up to hit their max torque and horsepower. Hell on my 6.4 max torque isn't until 4000 RPM, and my max horsepower is where most old big blocks redlined. She gets nervous when we're pulling hills at 4-5000 RPM with a trailer, while I'm just letting the thing run.

All that said, lower RPMs with a light/no load are better for longevity of a gas engine, as well as fuel mileage. This is where the overdrive gears and high gear ratios come into play - they let you get the motor down to really low RPMs while still keeping enough power to hold highway speeds.

I still say OP should look at gears if they plan on keeping the truck. They're relatively inexpensive, will wake the truck up a LOT out of the hole even pulling, and won't be a big hurt to the mileage.

If OP does go for a new truck to pull, but wants to stay gasser, I say grab a 6.4 truck but look for 4.10 gears at a minimum - skip the 3.73's as you'll be wanting to swap those out right away anyway. They're a capable enough gear but you're going to want more if you upsize your camper in the future.

 

[CamperMike]

As others have said let the engine rev when going up hills. Heck my hemi equipped truck has to rev when towing my similar sized tt through mountains and it doesn't scare me at all. Just use the gas pedal and watch temps. Especially oil temps as that is what heats up when towing up hills at least with my hemi.

 

[engineering]

The latest update:

A Sprintex supercharger is on the way for this truck.

I did quite a but of research on the components and stock engine. Cooling was my primary concern, but I think that has been addressed with this kit. The twin screw compressor (rather high efficiency) and front mounted intercooler along with it's conservative boost should keep the whole system in a good temp range even on hot days.

I think I will install the RIPP coilpacks while I have everything apart but otherwise no additional changes. The torque gain is significant and begins at very low RPM. I believe it is still within the torque handling capability of the transmission.

We have some mountain driving trips coming up with a total of about 3500 miles so it will be put to the test soon. I will do a few small test drives up some local mountains ahead of time just to make sure there are no surprises when the family is counting on it. Hoping that the provided tunes behave well out of the box. It will never see anything remotely resembling aggressive or race driving - pretty much just towing and hauling.

If it has any problems, it is modest task to pull it out and go back to bone stock.