Tow/Haul for a Uhaul 6x12?

[Dookie]

No.

I use tow/haul often, when I go on Sunday drives up in the mountains. It doesn't wait until it's lugging to downshift that way. It also compression brakes better on the downgrades. It will go into 8th gear if conditions are right and it does disable the MDS. I don't see how it's going to hurt anything. It's not like I'm locked down in 1st gear and winding it up to 60 mph

Agreed, and it turning off MDS is an added plus, I for one do not like MDS, the change in exhaust tone, the sluggish squishy pedal feel, the fact that 4 of the 8 cylinder temps are drastically different leads me to believe it may be a contributor to the exhaust manifolds cracking and/or manifold bolts breaking. Thermal cycling differentiation on a common piece is never a good thing, especially something cast iron. If I can easily disable (push a button) MDS I do, plus get the added benefit of holding the gear longer into the RPM range, engine braking (big benefit with 22's and oversized tires), added line pressure in the trans. for a less slip and cooler running trans., more nimble feel overall, the truck just feels quicker and lighter with tow/haul enabled.
MDS is there for the EPA, lawyers, and advertising numbers for MPG, I don't give a single F*ck about any of that, I just want my Hemi-powered Ram to feel like a Hemi-powered Ram.

 

[SpeedyV]

Agreed, and it turning off MDS is an added plus, I for one do not like MDS, the change in exhaust tone, the sluggish squishy pedal feel, the fact that 4 of the 8 cylinder temps are drastically different leads me to believe it may be a contributor to the exhaust manifolds cracking and/or manifold bolts breaking. Thermal cycling differentiation on a common piece is never a good thing, especially something cast iron. If I can easily disable (push a button) MDS I do, plus get the added benefit of holding the gear longer into the RPM range, engine braking (big benefit with 22's and oversized tires), added line pressure in the trans. for a less slip and cooler running trans., more nimble feel overall, the truck just feels quicker and lighter with tow/haul enabled.
MDS is there for the EPA, lawyers, and advertising numbers for MPG, I don't give a single F*ck about any of that, I just want my Hemi-powered Ram to feel like a Hemi-powered Ram.

I don't disagree with the "nimble feel" of Tow/Haul mode when unloaded; it is definitely more aggressive. I don't like that it kicks me out of Aero mode on the air suspension. I have also noticed zero difference (over hundreds of miles) in transmission temps when towing with or without T/H enabled, but I tested this only at highway speeds in cool weather. Stop-and-go in the summer might produce a different result, and I know I'd like the engine braking in that scenario.

As for MDS, the engine was designed for it from the beginning, and the 2009 revisions addressed potential long-term concerns. This is a quote about MDS from a Stellantis (then Chrysler) engineer at the time (sourced from Allpar): "The modern Hemi always shuts off the same four cylinders. In our durability test cycle (150,000 customer equivalent miles driven at the 95th percentile, meaning that only 5% of our owners are more abusive than our testing), we have not found any adverse wear patterns."

 

[Bt10]

I don't disagree with the "nimble feel" of Tow/Haul mode when unloaded; it is definitely more aggressive. I don't like that it kicks me out of Aero mode on the air suspension. I have also noticed zero difference (over hundreds of miles) in transmission temps when towing with or without T/H enabled, but I tested this only at highway speeds in cool weather. Stop-and-go in the summer might produce a different result, and I know I'd like the engine braking in that scenario.

As for MDS, the engine was designed for it from the beginning, and the 2009 revisions addressed potential long-term concerns. This is a quote about MDS from a Stellantis (then Chrysler) engineer at the time (sourced from Allpar): "The modern Hemi always shuts off the same four cylinders. In our durability test cycle (150,000 customer equivalent miles driven at the 95th percentile, meaning that only 5% of our owners are more abusive than our testing), we have not found any adverse wear patterns."

So you're saying 5% is the number of wiped cam lifters?

 

[SpeedyV]

So you're saying 5% is the number of wiped cam lifters?

Haha…fortunately those were improved after 2008, long before our trucks were a twinkle in a truck designer’s eye!

 

[Dookie]

I don't disagree with the "nimble feel" of Tow/Haul mode when unloaded; it is definitely more aggressive. I don't like that it kicks me out of Aero mode on the air suspension. I have also noticed zero difference (over hundreds of miles) in transmission temps when towing with or without T/H enabled, but I tested this only at highway speeds in cool weather. Stop-and-go in the summer might produce a different result, and I know I'd like the engine braking in that scenario.

As for MDS, the engine was designed for it from the beginning, and the 2009 revisions addressed potential long-term concerns. This is a quote about MDS from a Stellantis (then Chrysler) engineer at the time (sourced from Allpar): "The modern Hemi always shuts off the same four cylinders. In our durability test cycle (150,000 customer equivalent miles driven at the 95th percentile, meaning that only 5% of our owners are more abusive than our testing), we have not found any adverse wear patterns."

I wouldn't call a cracked manifold or broken manifold bolt a wear pattern either, but it was/is happening, it's not an if thing, it's a when thing. Something is causing it, the MDS and thermal cycling is JMO on the cause. I may be wrong, no shame in that, but I'll keep MDS off if I can for my personal reasoning.

 

[sdramsey24]

Do all of the new trucks have MDS? I've thought I felt it in the gas pedal but is there an indicator somewhere that tells when it's engaged or not? I haven't seen that idiot light on my dash yet!

 

[nc_beagle]

I understand what MDS does but not fully how. Why couldn't it alternate which four cylinders are cut off?

 

[SpeedyV]

I understand what MDS does but not fully how. Why couldn't it alternate which four cylinders are cut off?

You may want to search Google for "Hemi MDS", as there's a lot of info out there.

Long story short, it isn't designed that way (and doesn't really need to be, based on how it works). There are systems developed by other manufacturers that vary the cylinder deactivation process (different number of cylinders, different order of deactivation). The Chrysler/FCA/Stellantis method is actually fairly simple and robust—although a LOT happens in this "simple" approach.

Now that I think about it, there's a good article from Motortrend / Hot Rod that covers the details of MDS (and includes a POV about eliminating the system in older Hemis (up to 2011) intended for high-performance use. Check it out here: https://www.motortrend.com/how-to/chrysler-5-7l-hemi-mds-lifters/

 

[Dookie]

Do all of the new trucks have MDS? I've thought I felt it in the gas pedal but is there an indicator somewhere that tells when it's engaged or not? I haven't seen that idiot light on my dash yet!

All that are Hemi equipt have it, and as default the green "Eco" light in the dash cluster is disabled and you have to go into the settings to enable it if you want to see it in the cluster.

 

[sdramsey24]

You may want to search Google for "Hemi MDS", as there's a lot of info out there.

Long story short, it isn't designed that way (and doesn't really need to be, based on how it works). There are systems developed by other manufacturers that vary the cylinder deactivation process (different number of cylinders, different order of deactivation). The Chrysler/FCA/Stellantis method is actually fairly simple and robust—although a LOT happens in this "simple" approach.

Now that I think about it, there's a good article from Motortrend / Hot Rod that covers the details of MDS (and includes a POV about eliminating the system in older Hemis (up to 2011) intended for high-performance use. Check it out here: https://www.motortrend.com/how-to/chrysler-5-7l-hemi-mds-lifters/

Great read! Thanks for sending that along!

 

[AV8OR]

Crazy to think we used to tow things without a tow/haul button.

We used to have four on the floor and between the tach and our left foot we chose the shift points up and down hills.

 

[kymts]

I understand what MDS does but not fully how. Why couldn't it alternate which four cylinders are cut off?

Very good explanation here and also a possible cure for lifter/camshaft failure.

 

[SpeedyV]

We used to have four on the floor and between the tach and our left foot we chose the shift points up and down hills.

My dad taught me to drive stick on dump trucks and tractor-trailers. If you knew what you were doing, you’d rarely even need the clutch. Something satisfying about “knowing the machine” that is lost today.

 

[devildodge]

Why I will never sell my 99 8.0l V10 with NV4500

I hate that They program new trucks for comfort shifting and fuel mileage

These HEMI trucks need to spin near 4000RPM to be in the power. Everyone driving around in 7th and 8th gear...which are both overdrive never get to enjoy the engine.

Tow/haul mode is the way a truck used to be set up.

I then select 4th gear...which is direct drive(6th for you 8 speeders).

Then when i really want to feel like I am driving my ole trusty V10 Magnum...i select third...and the truck never shifts again...

The new trucks are worlds better than my 85,99 and 03...but man shifting gears and feeling the truck...priceless