2015 Pentastar V6 Towing [SUPERCHARGER SUCCESS!]

[engineering]

My wife recently inherited a 2015 RAM 1500 3.6L V6 2WD with 3.21 rear end (9k miles). We also have a 22ft 4600lb travel trailer. When it is fully loaded with cargo and people - we are right at the sticker limits of towing and GVWR. Legal, but barely.

As anyone can guess, this is fine at sea level on flat roads in cool weather, but the V6 cannot deal with any grades or high altitude when fully loaded. This is no surprise.

Because this was handed down from my father-in-law, my wife REALLY wants to keep it and make it work for towing. So, don't bother with the typical "Get the HEMI" or "Get the Diesel". Somehow, I want to figure out how to configure this truck to better deal with towing at max weight in hills and high altitudes.

The truck needs torque. I don't really care about HP in this case. I only want to be able to hold my speed going up hill without downshifting 2-3 gears and planting the RPM's at some crazy number for long stretches. At the moment, I just slow down to a crawl to get up hills without needing WOT. Not good.

Initially, I just thought that I would change the rear-end form 3.21 to 3.92 which gets me about 22% more torque. That is pretty significant and not a ton of money - about $1200 or so.

Perhaps I could also do a performance tune, coil packs, etc. for a bit extra.

The all-in play is to get a Sprintex supercharger kit that puts the V6 into HEMI territory which would certainly solve the problem for my little trailer. The obvious downsides are the $$$ and the warranty is voided. Not sure if the 3.21 'cruising' rear gearing would be stressed. This is an option with wife's stamp of approval for her late dads truck.


Any ideas or experiences related to maximizing the 3.6L V6 Pentastar for long distance towing in hills and high-altitudes? Is just a gearing change a dramatic difference in real life? Supercharger offers a big torque gain and at very low RPM where I need it. Maybe both?

 

[tron67j]

Sounds like some work is already on your radar. One suggestion i would make is look at your weight when towing, that also plays into your experience. Don't fill water tanks, buy groceries when at destination, don't carry more gear than you need. Can't tell how much never-used stuff I have pulled out my parent's and sisters' motorhomes and trailers when they go to sell them. Reducing weight is a free fix that everyone can start with. Good luck, and enjoy your truck!

 

[NewBlackDak]

Supercharged towing on long grades can become a heat issue really fast. I wouldn’t want a generic performance tuned supercharger for towing.

Start with trying to find a Hemi just like it, and sneak it past your wife… I know, I know.

Gears are the best bang for buck towing upgrade. Ported throttle body and a tune could help too.


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[engineering]

Supercharged towing on long grades can become a heat issue really fast. I wouldn’t want a generic performance tuned supercharger for towing.

As for the supercharger idea - there is only one practical option that I know of: Sprintex. Mainly because it is CARB legal (this is a California truck) and it is in-stock available.
It does use a twin screw compressor and an intercooler. It runs at rather modest boost so perhaps it would manage heat fairly well. I don't know and I don't know how to find out without buying it and towing up a long hill.
It is a very good topic to bring up. Maybe Sprintex can provide an answer. It appears to be a middle of the road design that is pretty conservative.

Start with trying to find a Hemi just like it, and sneak it past your wife… I know, I know.

A HEMI swap may be cheaper than trying to milk more power from the V6 - technically still the same truck sooooo......
Sounds like a fun project for another day.

Gears are the best bang for buck towing upgrade. Ported throttle body and a tune could help too.

Indeed - I am having a hard time anticipating just how much the jump from 3.21 to 3.92 will be. It is a 22% increase in wheel torque and maybe that is all I really need. Obviously gearing is FAR more simple and does not risk engine damage like an aftermarket supercharger kit.

 

[csuder99]

Keep in mind the transmission in the V6 is different from the Hemi or even the Ecodiesel. That might turn out to be the weak point when towing with a supercharged Pentastar.

Two devious ideas:
- Show her a smaller travel trailer that the V6 can easily handle
- Find a Hemi in the same color and trim and switch it out

 

[tidefan1967]

I like the gear swap as a starting point. I've had many a ride that was sluggish off the line that with just a gear swap turned into a "race" car. Start with that and if its not enough get a tuner(Does anybody do custom tunes for the 3.6? Hopefully somebody knows), a cold air intake and catback exhaust might help a little bit and who knows with all the changes it might be enough to satisfy you. I might also consider running a notch higher octane fuel when towing too just in case she pulls a little timing since every horse counts.

 

[crash68]

Somehow, I want to figure out how to configure this truck to better deal with towing at max weight in hills and high altitudes.

The truck needs torque. I don't really care about HP in this case. I only want to be able to hold my speed going up hill without downshifting 2-3 gears and planting the RPM's at some crazy number for long stretches. At the moment, I just slow down to a crawl to get up hills without needing WOT. Not good.

Initially, I just thought that I would change the rear-end form 3.21 to 3.92 which gets me about 22% more torque. That is pretty significant and not a ton of money - about $1200 or so

Your problem with low end torque is the spark plugs...you have them. To get to any of gassers torque band your going to need to rpms to get into the torque band, so climbing hills you'll be pushing 4K rpms.
I would try going with 3.92. Being it's a 2WD it might be cheaper to look at salvage yards to find a complete 3.92 rear axle and just swap.
Going with forced induction will help with power loss when climbing in altitude with naturally asperated engines. You'll probably probably have extra heat to deal with depending on how much boost.

 

[PoMansRam]

Given this is a 2wd, the gear swap is relatively simple and not invasive.

I would not try to mod the pentastar given the 8HP45 transmission like mentioned above. There's nothing bad about them, it's just they are rated to have less torque run through them than the 8HP70.

 

[2003F350]

As said above, if you (your wife) is dead-set on keeping the truck and using it for towing, your first step is gears. It's going to be the biggest bang for the buck, and it's going to make that little V6 scream out of the hole. Since you're a V6, it won't be as big of a hit to mileage either.

Having had a Grand Prix GTP with the M90 Eaton on top of a 3800, and playing around with the whole 'make it faster' crowd, a blower is going to make heat, and a lot of it, during climbing, especially if you can't get good airflow. We visited my sister and BIL in Washington State once in that car, and my ******* BIL decided to go slow up a twisting mountain road (we're talking like...15 mph). I had to stop halfway up because my temp gauge was up over 230° and wasn't coming down, even with my radiator fans running full speed. Mind you, this was a 3k-ish lb car, not towing, with 3 people in it. Granted I didn't have an intercooler yet, but even so, airflow is important.

If you do decide to go with a power adder, you're going to want the intercooler no question, but you're also going to need to make sure you can get as much airflow as possible to help with the cooling. I don't know if kits are available, but it may be better to go turbo - you'll get lag, but from my experience they don't heat up the engine compartment nearly as much.

 

[likes2build]

What did you pull the trailer with before? It's great to inherit a vehicle and love it because it is sentimental , especially only having 9k miles. Why can't you tow the trailer with the vehicle that towed it before? That way there you won't burn up the truck she loves. I have a Pentastar with a 3.21 rear so I feel the pain.

 

[ramffml]

I don't see how gears are going to help you out on the highway. Just downshift yourself one gear, and now you're sitting at the same gear you would have been in the 3.92.

Gears are not magic. You have 3 variables: speed (mph), rpm, and gear ratio. On the highway With either the 3.92 or the 3.21, you will be able to downshift and choose a better gear ratio to put your RPMs at the level you need, to maintain speed.

With the hemi and 8spd, the 3.92 in 8th has the exact same gear ratio as the 3.21 in 7th. Most of us with the 3.21 run around towing in 6th, and that is the same gear ratio as the 3.92 in 7th.

Now taking off from a dead stop, that is where the 3.92 will help. But on the highway, that's the whole point of a transmission, to put your RPMs where you need them.

If two trucks are going down the road at the same speed, and at the same RPM, then they are both running the same gear ratio (though they may be in a different numerical gear number which is completely unimportant).

You seem to be wanting to negate the need for downshifting, but the 3.92 won't help you there. If your engine needs 4000 RPMs to travel up a hill at load, your transmission will downshift as many gears as needed to get you there, that's the same for both 3.21 and 3.92. If the 3.21 needs 4000 rpms to get over the hill, the 3.92 will need the same rpms.

 

[Fishstickz]

As others have said, gears are one of the things you can do. But with y’alls 8 speed transmissions, differential gears are less important since you could just lock out 7th and 8th and be running the same RPM as you would in 8th with 3.92s or 4.10s.

Gear swaps were one of the best things to do with the old RFE’s in the 4, 5, or 6 speed flavor, but now with the 8 speed and being able to manually lock out some of those OD gears you have a lot more flexibility in highway driving. The main advantage you’d still get from a gear swap is better acceleration from a stop which would at least help getting that load moving a little easier


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[yillbs]

Is the truck able to GET up the hills safely? Dropping some gears isn't a bad thing, the engine is designed to be loud and obnoxious in the high rev band.

 

[likes2build]

@engineering input your vin into the link below and it ill give you your exact vehicle specs.

https://www.ramtrucks.com/towing/towing-guide.html

If I understand GVWR correctly it's tied to the VIN# and swapping gears won't ever increase it as far as LEO and tickets is concerned. Gears will help taking off from a dead stop, that's all with an 8 spd.

 

[rule18]

Your problem with low end torque is the spark plugs...you have them. To get to any of gassers torque band your going to need to rpms to get into the torque band, so climbing hills you'll be pushing 4K rpms.
I would try going with 3.92. Being it's a 2WD it might be cheaper to look at salvage yards to find a complete 3.92 rear axle and just swap.
.

^This. I have a 3.6 with 3.92 gears and when I tow (not that often) it's less weight than you pull. Expect to be in the 3k to 4k range for power, which for the Pentastar is not necessarily a bad thing. Oh, and welcome to RamForum!

 

[engineering]

@engineering input your vin into the link below and it ill give you your exact vehicle specs.

https://www.ramtrucks.com/towing/towing-guide.html

If I understand GVWR correctly it's tied to the VIN# and swapping gears won't ever increase it as far as LEO and tickets is concerned. Gears will help taking off from a dead stop, that's all with an 8 spd.

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.

I don't see how gears are going to help you out on the highway. Just downshift yourself one gear, and now you're sitting at the same gear you would have been in the 3.92.

Gears are not magic. You have 3 variables: speed (mph), rpm, and gear ratio. On the highway With either the 3.92 or the 3.21, you will be able to downshift and choose a better gear ratio to put your RPMs at the level you need, to maintain speed.

With the hemi and 8spd, the 3.92 in 8th has the exact same gear ratio as the 3.21 in 7th. Most of us with the 3.21 run around towing in 6th, and that is the same gear ratio as the 3.92 in 7th.

Now taking off from a dead stop, that is where the 3.92 will help. But on the highway, that's the whole point of a transmission, to put your RPMs where you need them.

If two trucks are going down the road at the same speed, and at the same RPM, then they are both running the same gear ratio (though they may be in a different numerical gear number which is completely unimportant).

You seem to be wanting to negate the need for downshifting, but the 3.92 won't help you there. If your engine needs 4000 RPMs to travel up a hill at load, your transmission will downshift as many gears as needed to get you there, that's the same for both 3.21 and 3.92. If the 3.21 needs 4000 rpms to get over the hill, the 3.92 will need the same rpms.

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.

 

[engineering]

^This. I have a 3.6 with 3.92 gears and when I tow (not that often) it's less weight than you pull. Expect to be in the 3k to 4k range for power, which for the Pentastar is not necessarily a bad thing. Oh, and welcome to RamForum!

Thanks for having me - it seems like a well informed and respectful community.

Do you think that continuous 3.5k RPM is ok for this engine? I only have gut feelings to go on, but it sounds like it is only ok with those RPMs during initial acceleration. Driving it what way for 10's of thousands of miles makes me nervous about the longevity.

 

[rule18]

Thanks for having me - it seems like a well informed and respectful community.

Do you think that continuous 3.5k RPM is ok for this engine? I only have gut feelings to go on, but it sounds like it is only ok with those RPMs during initial acceleration. Driving it what way for 10's of thousands of miles makes me nervous about the longevity.

I do think so but conversely, I don't think you'd be in that range all the time. Go here and ask some questions, there are lots of 3.6 owners here. https://www.ramforum.com/forums/v6-engine-performance.206/

 

[MVM1]

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.

 

[crash68]

When the 'Tow Mode' is active, the overdrive gears are locked out and the truck never goes past 6th.

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

Do you think that continuous 3.5k RPM is ok for this engine? I only have gut feelings to go on, but it sounds like it is only ok with those RPMs during initial acceleration. Driving it what way for 10's of thousands of miles makes me nervous about the longevity.

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.