68RFE Towing Guide: Tow/Haul Mode, Temperatures, Overdrive, Tire Size & Reliability
The 68RFE transmission can be a good towing transmission when it is healthy, properly maintained, correctly operated, and matched to the truck's rated towing capacity. However, towing places substantially more demand on the 68RFE's torque converter, valve body, hydraulic system, Overdrive clutches, and cooling system than unloaded driving.
For Ram 2500 and Ram 3500 owners who tow regularly, the way the transmission is operated can have a major effect on its longevity.
At Next Gen Drivetrain, our in-house engineering department pays particular attention to the 68RFE's hydraulic system because towing increases the amount of clutch holding force the transmission requires.
A clutch cannot hold additional towing load simply because the engine has enough power to pull the trailer.
It also needs sufficient hydraulic apply pressure.
That is why, for an otherwise healthy 68RFE that will regularly tow heavy loads, Next Gen Drivetrain recommends an upgraded valve body as one of the most valuable preventative transmission upgrades.
Quick Answers: 68RFE Towing Questions
| Question | Short Answer |
|---|---|
| Is the 68RFE good for towing? | Yes, within the truck's rated capacity and when properly maintained and operated. |
| How much can I tow? | Follow the specific truck's GVWR, GCWR, axle, payload and trailer ratings—not a generic transmission limit. |
| Should I tow in sixth gear? | Yes when the truck can hold sixth steadily without lugging, hunting or excessive heat. |
| Should I lock out Overdrive? | Not automatically. Limit upper gears when the transmission repeatedly hunts or struggles on grades. |
| Should I use Tow/Haul? | Yes for heavy towing, hills and conditions that cause frequent shifting. |
| What temperature is too hot? | Sustained temperatures substantially above normal deserve attention; Next Gen considers 220°F+ a reason to watch closely and 240°F+ a serious warning condition. |
| Should I manually downshift on grades? | Yes when needed to reduce hunting, converter slip and heat, while staying within safe engine RPM. |
| Do larger tires hurt the 68RFE? | They can increase effective drivetrain load and heat. |
| Should I regear for 35s or 37s? | Often yes, particularly on a truck that tows heavily. |
1. Is the 68RFE Good for Towing?
Yes. The 68RFE can tow very effectively when used within the vehicle's ratings.
Ram specifically designed the transmission control strategy to accommodate towing, and the owner's manual recommends using Tow/Haul mode or a lower Electronic Range Select gear limit when heavy loading causes excessive shifting. Ram states that doing so can reduce heat buildup and help extend transmission life.
The issue is not that the 68RFE is incapable of towing.
The bigger issue is what sustained towing does to the transmission.
Heavy trailers increase:
- Torque converter load
- Clutch holding requirements
- Hydraulic demand
- Transmission temperature
- Shift frequency
- Overdrive clutch loading
- Cooling-system demand
A completely stock truck towing occasionally presents a much easier environment than a tuned Cummins on 37-inch tires pulling a large fifth wheel through the mountains.
What is the biggest concern when towing with a 68RFE?
From Next Gen Drivetrain's engineering perspective, hydraulic integrity is extremely important.
The pump creates transmission pressure, but the valve body must accurately regulate and route that pressure to the clutch circuits.
As towing load rises, clutch holding requirements increase.
If internal hydraulic leakage reduces the effective pressure reaching a clutch, the clutch can begin slipping.
That creates the failure sequence:
Heavy load + inadequate clutch pressure → slip → heat → friction damage → transmission failure
This is one reason our in-house engineering department recommends improving the 68RFE valve body before regularly subjecting the transmission to severe towing duty.
2. How Much Weight Can I Tow With a 68RFE?
There is no single trailer-weight rating for every 68RFE-equipped truck.
Your transmission alone does not determine towing capacity.
Towing capacity depends on:
- Ram 2500 versus Ram 3500
- 2WD versus 4WD
- Cab configuration
- Bed length
- Axle ratio
- GVWR
- GCWR
- Curb weight
- Payload
- Hitch type
- Trailer tongue or pin weight
- Factory equipment
For example, Ram's 2024 Heavy Duty towing chart shows 6.7L Cummins/68RFE combinations with maximum trailer ratings ranging considerably by configuration. Certain Ram 2500 combinations approach 20,000 pounds, while properly configured Ram 3500 trucks equipped with the standard-output Cummins and 68RFE were rated as high as approximately 22,660 pounds.
That does not mean every 68RFE truck can tow 22,660 pounds.
The same factory chart specifically states that GVWR, GAWR and GCWR must not be exceeded and that trailer and payload ratings depend on vehicle configuration.
So how much can your 68RFE truck tow?
Use the rating for your exact vehicle configuration.
Do not choose trailer weight based on what another Cummins owner with a different cab, axle, chassis or transmission is towing.
At Next Gen Drivetrain, we would also separate two questions:
What is the truck legally/factory rated to tow?
and:
How severe is that load on the transmission?
A truck may be within its published tow rating while still spending much of its life under severe transmission duty.
3. Should I Tow in Sixth Gear With a 68RFE?
Yes—when operating conditions allow the transmission to remain comfortably in sixth gear.
The 68RFE does not need to be prevented from using sixth gear simply because a trailer is attached.
Ram's owner's manual allows the transmission to remain in DRIVE while towing and relies on the transmission's towing strategy to select appropriate gears.
Sixth gear is generally appropriate when:
- The road is relatively flat
- Vehicle speed is stable
- The torque converter remains properly controlled
- The truck is not lugging
- The transmission isn't repeatedly downshifting
- Transmission temperature remains controlled
When should you stop forcing the 68RFE to stay in sixth?
If you notice:
6th → 5th → 6th → 5th → 6th
every time the grade or throttle position changes, sixth is no longer helping.
Repeated gear changes increase hydraulic activity and clutch cycling and can add heat.
Ram specifically advises using Tow/Haul or selecting a lower gear range when heavy loads or hills cause frequent shifting.
Let the engine operate at a slightly higher RPM rather than forcing the transmission to constantly hunt for the highest possible gear.
4. Should I Lock Out Overdrive While Towing?
Not automatically.
There is no need to permanently eliminate the upper gears every time you connect a trailer.
Instead, use the Electronic Range Select (ERS) system intelligently.
ERS lets the driver choose the highest gear the transmission is allowed to use. For example, selecting 5 allows gears 1 through 5 while preventing sixth gear; selecting 4 restricts the transmission to gears 1 through 4.
Lock out sixth when:
- The transmission repeatedly shifts between fifth and sixth
- The truck struggles to maintain speed
- Engine RPM becomes excessively low under heavy load
- Transmission temperature begins climbing
- You are climbing a significant grade
On a steeper grade, limiting the transmission to fourth or another appropriate gear can be beneficial.
Ram specifically states that selecting a lower gear under heavy load can reduce excessive shifting and heat buildup and improve transmission life.
The goal isn't the lowest RPM possible.
The goal is efficient torque transfer with minimal unnecessary clutch and converter slip.
That distinction is important when trying to keep a 68RFE alive.
5. Should I Use Tow/Haul Mode With the 68RFE?
Yes. Tow/Haul mode should generally be used when towing a substantial trailer, particularly in hilly terrain or whenever the transmission begins shifting frequently.
Ram specifically recommends Tow/Haul when:
- Towing
- Carrying heavy loads
- Driving in hilly terrain
- Frequent shifting occurs
Tow/Haul alters transmission operation by delaying upshifts and providing more aggressive automatic downshifting for engine braking. Ram states that this helps improve performance and reduces the potential for overheating or transmission failure caused by excessive shifting.
Why does Next Gen Drivetrain recommend Tow/Haul?
Because constantly shifting in and out of gears creates additional clutch application events.
Fewer unnecessary shifts generally mean:
- Less clutch cycling
- Less heat generation
- Better engine braking
- More stable operating temperature
For diesel trucks equipped with the factory exhaust brake, Tow/Haul becomes even more useful.
Ram states that the automatic transmission downshifts more aggressively with the exhaust brake enabled in Tow/Haul mode, and recommends combining the two for optimum braking performance.
6. What Transmission Temperature Is Too Hot for a 68RFE?
There is an important distinction between normal operating temperature and damaging sustained heat.
Ram does not give owners a simple universal number such as:
“At exactly 225°F the transmission is overheating.”
Instead, the control system monitors temperature and changes transmission behavior when temperatures exceed its normal operating limits. If conditions become severe enough, the Transmission Temperature Warning Light illuminates. Ram warns that continuing to drive with that warning illuminated can cause severe transmission damage or failure.
Next Gen Drivetrain's practical temperature guidance
For owners monitoring transmission temperature while towing, our approach is conservative:
Under approximately 200°F: Generally a comfortable operating range during normal towing.
200–220°F: Not automatically a failure condition, especially during a temporary grade, but monitor the trend.
Sustained 220°F+: We would begin asking why the transmission is producing or retaining that much heat.
Around 240°F or higher: Treat this as a serious condition and reduce the load on the transmission rather than accepting it as routine operation.
Transmission temperature warning illuminated: Follow the manufacturer's cool-down procedure immediately.
The trend matters as much as the number.
A truck that has always towed the same trailer at 180–195°F and suddenly begins reaching 220–230°F under identical conditions may be telling you something has changed.
Possible causes include:
- Torque converter clutch slip
- Transmission clutch slip
- Low fluid
- Hydraulic pressure loss
- Restricted cooler flow
- Increased load
- Cooling-system problems
Don't automatically solve overheating with a bigger cooler.
A larger cooler can remove additional heat.
But if a clutch is actively slipping because of inadequate hydraulic pressure, the correct solution is to stop the clutch from slipping.
That principle is central to Next Gen Drivetrain's valve-body engineering.
7. Should I Manually Downshift the 68RFE on Steep Grades?
Yes, when necessary.
The 68RFE's ERS system is specifically designed to let the driver limit the maximum available gear.
Ram advises using a lower gear range on severe grades and states that doing so can reduce excessive transmission shifting and heat buildup.
When climbing a grade
Downshift or limit the upper gear if:
- Engine RPM is too low for the load
- The transmission constantly hunts
- The torque converter is generating excessive heat
- Transmission temperature is climbing
- The truck cannot comfortably maintain speed
Ram also specifically notes that low-speed towing up a steep grade can generate significant converter heat and recommends downshifting to an appropriate lower gear to reduce that heat generation.
When descending a grade
Use:
- Tow/Haul
- Factory exhaust brake
- Appropriate ERS gear limiting
rather than relying entirely on the service brakes.
Ram's exhaust-brake system is specifically intended for towing applications and can reduce brake fade and mechanical brake usage.
Do not select a gear that causes unsafe engine overspeed. Ram explicitly cautions against overspeeding the engine when using ERS for downhill braking.
8. Do Larger Tires Hurt the 68RFE?
Larger tires can increase the load experienced by the 68RFE, particularly during acceleration and towing.
Increasing tire diameter effectively makes the truck's axle gearing taller.
That means the drivetrain must work harder to produce the same force at the ground.
Potential effects include:
- More converter slip during acceleration
- Higher clutch load
- Increased heat
- More frequent downshifting
- Lower engine RPM at a given road speed
- Increased tendency to lug under load
This becomes particularly significant when combining:
larger tires + heavy trailer + added engine power + factory axle gearing.
Each individual modification may seem manageable.
Together, they can substantially increase transmission demand.
Why Bigger Tires Can Be Hard on a Stock 68RFE
Imagine replacing approximately 33-inch factory tires with 37-inch tires.
The increase isn't simply cosmetic.
A 3.73 axle ratio with significantly larger tires behaves like a numerically lower axle ratio.
That means the torque converter and transmission have to make up some of the mechanical disadvantage.
The driver may compensate by using additional throttle.
Now clutch pressure and converter efficiency become even more important.
This is another reason our Next Gen Drivetrain in-house engineering department recommends addressing hydraulic integrity when building a Cummins truck around heavy towing, larger tires, or additional power.
9. Should I Regear My Ram After Installing 35- or 37-Inch Tires?
For a lightly driven truck, not always.
For a truck that tows heavily, regearing becomes much more compelling—particularly with 37-inch tires.
The basic relationship is:
New axle ratio ≈ original axle ratio × new tire diameter ÷ original tire diameter
For example, assuming approximately a 33-inch original tire and 3.73 gears:
Moving to 35-inch tires
3.73 × 35 ÷ 33 ≈ 3.96
A 4.10 axle ratio would therefore bring the effective gearing fairly close to the original relationship.
Moving to 37-inch tires
3.73 × 37 ÷ 33 ≈ 4.18
A ratio in the 4.10–4.30 neighborhood moves the drivetrain closer to its original mechanical leverage, while an even deeper ratio may make sense for exceptionally heavy towing depending on the truck and intended cruising speed.
These are examples—not universal prescriptions.
The correct ratio depends on:
- Original tire size
- Current axle ratio
- New tire diameter
- Trailer weight
- Typical highway speed
- Terrain
- Engine modifications
- Desired cruising RPM
Why Regearing Can Help the 68RFE
Proper axle gearing moves some of the workload away from the transmission.
Instead of asking the torque converter and clutch packs to overcome a tall effective final-drive ratio, the axle supplies more mechanical leverage.
For a serious tow vehicle on 37-inch tires, we generally prefer appropriate gearing rather than forcing the transmission to compensate for tire size indefinitely.
Why Towing Makes the 68RFE Valve Body More Important
The more load you place on a transmission, the more important clutch holding force becomes.
Consider a lightly loaded truck.
A clutch might have considerably more holding capacity than the torque being applied to it.
Now connect a heavy trailer.
The Cummins requires more throttle and produces more torque.
The transmission now needs greater clutch holding force.
If the valve body has an internal hydraulic leak, the margin between:
available clutch holding force
and
engine torque
gets smaller.
Eventually:
Engine torque exceeds available clutch holding force → clutch slips.
That is why towing often exposes hydraulic weaknesses that may never have been obvious during unloaded driving.
Why Next Gen Drivetrain Recommends a Valve Body Upgrade for 68RFE Tow Vehicles
For an otherwise healthy transmission, Next Gen Drivetrain considers the valve body one of the first upgrades we would perform on a dedicated 68RFE tow vehicle.
Why the valve body?
Because the valve body can be upgraded without performing a complete transmission rebuild, yet it controls the hydraulic system responsible for applying the transmission's clutch packs.
Our in-house engineering department does not simply assemble a valve body using generic aftermarket components.
Next Gen Drivetrain states that its Project Carbon® RFE valve-body technology is engineered and manufactured in-house, with proprietary work involving valve design, hydraulic circuits, separator/channel plates, accumulator systems and other areas of the RFE hydraulic system.
Our engineering process includes analysis of:
- Hydraulic circuitry
- Valve geometry
- Component materials
- Internal leakage
- Line-pressure stability
- Shift timing
- Clutch holding requirements
Next Gen Drivetrain also states that completed valve bodies are tested for hydraulic operation, line pressure, solenoid response and internal leakage before shipment.
The objective is not simply harder shifts.
A towing transmission does not need to bang violently into every gear.
It needs:
fast clutch application + adequate pressure + low hydraulic leakage + predictable shift timing.
That is the philosophy behind our in-house RFE engineering.
Is a Valve Body Upgrade Necessary if My 68RFE Is Still Stock?
We believe it can be a worthwhile preventative upgrade even for an otherwise stock Cummins—particularly if the truck regularly tows.
Towing increases load even when engine horsepower has never been modified.
An owner pulling a 15,000-pound fifth wheel every week can place substantially greater sustained demand on the transmission than someone driving a tuned truck unloaded to work every day.
Hydraulic integrity therefore matters to:
- Stock trucks
- Tuned trucks
- Work trucks
- Fifth-wheel tow vehicles
- Commercial vehicles
- Trucks with oversized tires
The ideal time to improve the hydraulic system is while the existing clutch packs are still healthy.
Once clutches have been severely overheated or burned, no valve body can restore the destroyed friction material.
Next Gen Drivetrain's 68RFE Towing Checklist
If long-term 68RFE reliability is the goal, we recommend:
- Stay within the exact truck's published towing and axle ratings.
- Use Tow/Haul when towing substantial loads or driving in hilly terrain.
- Allow sixth gear when conditions are easy—but don't force the transmission to stay there.
- Use ERS to limit upper gears when the transmission begins hunting.
- Downshift appropriately on steep grades.
- Use the factory exhaust brake when applicable.
- Monitor transmission temperature rather than waiting for a warning light.
- Investigate unexplained increases in transmission temperature.
- Keep the correct transmission fluid properly serviced and filled.
- Consider axle gearing when installing significantly larger tires.
- Do not continue heavy towing if the transmission is slipping or flaring.
- Upgrade the valve body before hydraulic problems have an opportunity to damage the clutch packs.
Frequently Asked Questions About Towing With a 68RFE
Can a stock 68RFE tow 15,000 pounds?
Many factory 68RFE-equipped Ram Heavy Duty configurations are rated for trailers in that range or higher, but the specific truck's published rating must always be checked.
Ram's 2024 factory chart shows 68RFE-equipped trucks with ratings ranging from below 15,000 pounds to more than 22,000 pounds depending on configuration.
Is sixth gear bad for the 68RFE while towing?
No.
Sixth gear is not inherently bad.
It becomes undesirable when the truck cannot maintain it efficiently and begins constantly shifting, lugging or generating excessive heat.
Is fifth gear better than sixth for towing?
It can be under heavier load or moderate grades.
If limiting the transmission to fifth stops repeated 5-6 hunting and keeps the engine in a more useful RPM range, fifth may be the more efficient and transmission-friendly choice.
Should I tow with Tow/Haul on all the time?
For substantial trailers, especially through hills or conditions that produce frequent shifting, yes, Tow/Haul is generally appropriate.
Ram specifically recommends it for these conditions.
Is 200°F too hot for a 68RFE?
Not by itself.
A temporary temperature around 200°F during towing does not automatically indicate a problem.
We become more interested in whether temperature continues climbing, remains elevated, or is substantially higher than the truck historically operated under the same conditions.
Is 220°F too hot for a 68RFE?
A brief excursion during a demanding grade is different from operating at 220°F or higher continuously.
Next Gen Drivetrain recommends treating sustained temperatures above roughly 220°F as a reason to reduce load and investigate why the transmission is generating so much heat rather than considering it an ideal normal operating target.
Is 240°F too hot for a 68RFE?
We would consider 240°F a serious temperature condition rather than a desirable towing temperature.
Reduce load and determine whether clutch slip, converter slip, fluid condition, cooling performance or another problem is responsible.
If the factory Transmission Temperature Warning Light illuminates, follow Ram's cool-down instructions immediately.
Should I tow in fourth gear up a mountain?
If fourth is the gear that allows the engine to maintain the climb without excessive hunting, lugging or converter heat, yes.
Ram specifically recommends selecting lower gear ranges on severe grades when necessary.
Are 37-inch tires hard on a 68RFE?
They can be, particularly with factory axle gearing and a heavy trailer.
The increased tire diameter reduces effective mechanical leverage, requiring more work from the engine, converter and transmission.
Should I regear with 35-inch tires?
Not every truck needs to.
But for a dedicated tow vehicle, restoring gearing closer to the factory effective ratio can improve drivability and reduce unnecessary transmission load.
Should I regear with 37-inch tires?
For a truck that regularly tows heavy, we would strongly consider it.
The jump from a roughly factory-size tire to 37 inches is substantial enough to materially change effective gearing.
The Bottom Line: Is the 68RFE a Good Towing Transmission?
Yes—but it needs to be treated like a transmission working behind a high-torque diesel truck, not like an unloaded passenger-car transmission.
Use Tow/Haul.
Let it downshift.
Don't force sixth gear up every hill.
Use ERS when it begins hunting.
Monitor temperature.
Consider axle gearing when dramatically increasing tire size.
And most importantly, don't ignore the hydraulic system that makes the entire transmission work.
At Next Gen Drivetrain, our in-house engineering department views the 68RFE valve body as one of the most important areas to address on a truck that will spend its life towing.
The reason is straightforward:
More trailer weight requires more torque transfer.
More torque transfer requires greater clutch holding force.
Greater clutch holding force depends on adequate, accurately controlled hydraulic pressure.
A mechanically healthy clutch can still be damaged if the hydraulic system does not apply it firmly enough.
That is why we recommend a Next Gen Drivetrain upgraded 68RFE valve body as a preventative reliability upgrade for owners who intend to work their trucks hard.
Our philosophy isn't to wait until a towing problem burns up a clutch pack and then replace the damaged parts.
It is to use in-house engineering to identify the weaknesses that contribute to those failures and improve them before the transmission has a reason to fail.
