Tow/haul mode gas engine discussion

[KyDan]

There is an active recent thread here-
http://www.forestriverforums.com/for...ml#post2143806\
about a half ton gas truck with tow/haul mode issues.

I'm starting this thread so as not to derail that thread. In that thread several folks mention that a gas engine has no real engine braking. Often the people who give this opinion are driving heavy rigs and diesels.

I'm driving a V8 5.6L GASSER with 7 sp tranny. I tow a 29' regular trailer that weighs around 7500 LOADED ready to camp.
On a 7000+ mile trip from KY north and then west all the way to the coast of Washington then south along US101 we encountered plenty of mountains. While we didn't cross the highest passes we did have several 6% grades and one or two as steep as 9% (I think it was 9-might have been 8...)
I never felt like I was over using my brakes. On many of the descents I only tapped my brakes and the tranny in tow haul mode down shifted appropriately and kept my speed where it needed to be.
I could feel plenty of engine braking.

Just saying you diesel guys who tow big rigs in the 12,000-15,000+ Lb range seem to look down on us guys who drive gassers. My truck tows and slows my 7500 LB trailer just fine- including reasonable engine braking when needed.

[david_reaves]

Yep. My 6.4 L Hemi in my Ram 3500 SRW likewise does a great job managing hills using tow/haul mode and engine braking. It will also maintain downhill speed using engine braking with the cruise control set to a moderate speed. I'm pulling a 35' ultralight camper fully loaded at about 8600 lbs. I'm sure that it doesn't hurt that the curb weight of the truck, with gear and me loaded, is close to 8000 lbs. There is plenty of truck to push back on the trailer!

But no, braking using the engine and transmission isn't the same as an exhaust brake or the other option, a Jacobs "jake" engine brake on diesel engines. It performs a similar function, though, which is to reduce dependence on the brakes themselves and to reduce brake wear and keep the brakes cool enough to use when they ARE required.

For my current setup, we've driven probably 30,000 miles of mountain driving. That's been on eastern and western slopes of the Rockies in Colorado and New Mexico as well as the Appalachians in the East. The gas engine also manages the flat land between pretty well, too.

[emm-dee]

I agree. My last rig was average 9,000 pounds pulled with a Ram 1500 and eight speed tranny. Replaced with Ram 2500 diesel and main difference was engine RPM when going down 6.2 percent a couple times a month. The diesel dropped two gears, the gas three, sometimes four, gears. The diesel never seemed to work as hard but both had the same result.

Also, I did use the trailer manual brake control at times. Let the speed creep up to about 65, tap the trailer brakes to bring it back to 55 or so. And...before y’all say never do that keep in mind the trailer had a very strong disc brake system.

[B and B]

I have towed with many a Pickup F 150 (4) gas engines and a 3/4 E 250 Club Wagon with a 351 and a Mercury Marquais sedan with a 351 variable venturi carb and a GMC Safari (biggest piece of crap ever 4.3l)

All provide engine braking, not what my current Diesel Suoerduty can provide. No replacing it.

I also had a Nissan Titan as a leased work truck but never towed and a 1990 Dodge Durango used as a commuter truck.

The Mercury and Club Wagon where 4 speed transmissions and locked in third all the time as a replacement for tow/haul mode. They worked and I relied on trailer brakes to stop it, a 23 ft Corsair Travel Trailer running bias ply snow tires (cheap tires from the staff factory store).

I was in the rockies with a company E450 cube truck over weight and it was screaming all the way down but the 460 V8 did slow it down dn a great job. The front pads they were smoking. Needless to say that van had a brake job in Vancouver and the load was split up and freight shipped back to Ontario.

[Matheny9]

I have a 2015 Chevy 2500HD, in tow/haul it also has engine braking. Works well on grades.

[CurtPutnam]

Gas engine braking exists. As kids, driving the family car, how many times did you downshift on off-ramps, tight curves, etc? My dad was an M.E. and I asked him about the practice (his cars after all). He thought about it a bit and then said: "brakes are cheaper than transmissions."

Gas engine braking may not as profoundly effective as with diesel but it does useful work. We have now run around much of CA and AZ with our new-ish truck and hit grades to 8%. Tow/Haul + Cruise Control combined to give us very controlled descents with only occasional taps on the brakes.

JMO & YMWV

[Blackrock]

I'm running a RAM 1500 5.7 with the 8spd transmission towing a 8,000# 5th wheel. Using tow/haul mode and cruise control I have good control on any of these Arizona mountain grades. Sometimes I will just toggle the trans to 3rd or 4th gear and use light braking on the 6% downhill of the highway 60 portions of the Salt River Canyon. Same going up the other side to prevent upshift and lugging. This truck has a sweet spot of around 2800 to 3200 RPM for pulling the steeper grades.

[67L48]

For many people, it's simply called downshifting and they're unable to make a link to the concept of "engine braking."

I think people conflate the automatic features of newer rigs and the diesel exhaust restrictions with good old fashioned engine braking. Downshift and use the natural resistance of the engine's higher RPMs to help slow the vehicle. Done and done.

May not be automatic. It's not automatic in my 2005 5.4L F-150 with Tow Package. There's no Tow/Haul Mode. There is an O/D Lockout button that restricts the transmission to gears 1-3. But, that doesn't change shift points and such the way that modern Tow/Haul Modes do now. However, I can also manually shift to 2 on my automatic shifter. So, again, engine braking can be done manually by downshifting.

[Trawlerphil]

After 35K miles towing a 9K Flagstaff Classic 5er with a 5.7 Tundra through every mountain range in the country, I can safely say "beast mode"--AKA tow/haul mode with the nannies off and paddle shifting works just fine.

[DouglasReid]

Originally Posted by KyDan

Just saying you diesel guys who tow big rigs in the 12,000-15,000+ Lb range seem to look down on us guys who drive gassers.

Dan,

I would hope that no diesel driver looks down on you for driving a gasser. Both engines have their good and bad points.

If we had a smaller camper Id possibly be driving a gasser too. The biggest downside I see is the mileage and the resulting need to stop much more frequently for fuel.

I do have a question, does your transmission have a "manual" mode so you can shift gears yourself rather than letting the transmission decide what gear you are in?

If so, you may be able to use Cruise Control and Manual Mode to take full advantage of the compression braking that gas engines have to keep yourself from having to use the brakes much if at all on downslopes.

Granted, you cannot go fast, but a steady slower speed that saves the extreme wear and tear on your brakes and prevents Brake Fade from overheating them.

[PaulRod]

I have a 2018 F150 that tows our TT. We went to Pennsylvania from Florida last summer. I put it in drive and Tow/Haul and never looked back. The truck did all the work.

[JimMorrell]

As I've said before, my 5.0 L engine in a 2011 F 150 4x4 4dr, doesn't have as much braking power as an older high compression gasser, or most diesels, but it keeps me from getting nervous going down an 8% grade, and in northern California, I encounter many of them. Learn how Tow Haul is intended to work, and you'll probably then be satisfied.

[emm-dee]

My current ride is a Forester built on the Ford E450 chassis. The auto downshifting when touching the brakes with tow/haul selected works great. I’m sure it’s not true but it sure does seem that Ford added five or six extra gears only used for engine braking.

Other than that I have nothing good to say about the Ford chassis. I guess it’s reliable since it was designed back in the early 60’s and hasn’t been updated since then.

[JPin AZ]

I have towed my 23ss with my 2003 1500 5.3 V8 4 speed auto trans Avalanche from Flagstaff to Phoenix twice now. 145 miles, 5500 feet elevation change, many miles of it at least 5%. Both times traffic was on my side and I did not brake once. I used tow haul and third gear doing 65 mph on the up and down grades. If I do have to brake I do it on the straights and then very lightly accelerate around the corners, from what I read on the other post doing this may avoid the excessive down shifting on the Ford. Engine braking works, I wish more people understood it.

[Greg in michigan]

I owned a 2004 Nissan titan and loved the truck. Pulled a 5800 lbs empty ( never weight it loaded ) tt from Michigan to Florida 9 times plus who knows how many shorter trips. Planning for retirement and farther trips ( retired 1/1/19 ) we bought a new tt thats 6400 lbs empty, 8000 max and a new at that time 2018 Nissan titan xd Cummins turbo diesel.
What a difference between the reg titan and the xd. Reg titan was somewhere around 5400 lbs xd is around 69l00 lbs. It doesn't had a jake brake but in toe mode once I touch the brake the down shifting is radically different in tow mode then when off. Must be it change's when it down shiftes as I can stop with just barely touching the brake.
So far in the year we've owned it wife and I are enjoying it.
Now if they only had put a bigger fuel tank.
Greg in Michigan
2019 rockwood 2606ws
2018 Nissan titan xd Cummins turbo diesel

[dcheatwood]

I think the confusion is in under standing the phrase "engine braking."
Diesels brake by the exhaust gas in the 'Engine.'
Gassers break by transmission holding lower gears.
So technically, gassers have transmission braking, not engine braking.
*And I'm glad to have it on my Class C E450.

[TitanMike]

Originally Posted by Greg in michigan

I owned a 2004 Nissan titan and loved the truck. Pulled a 5800 lbs empty ( never weight it loaded ) tt from Michigan to Florida 9 times plus who knows how many shorter trips. Planning for retirement and farther trips ( retired 1/1/19 ) we bought a new tt thats 6400 lbs empty, 8000 max and a new at that time 2018 Nissan titan xd Cummins turbo diesel.
What a difference between the reg titan and the xd. Reg titan was somewhere around 5400 lbs xd is around 69l00 lbs. It doesn't had a jake brake but in toe mode once I touch the brake the down shifting is radically different in tow mode then when off. Must be it change's when it down shiftes as I can stop with just barely touching the brake.
So far in the year we've owned it wife and I are enjoying it.
Now if they only had put a bigger fuel tank.
Greg in Michigan
2019 rockwood 2606ws
2018 Nissan titan xd Cummins turbo diesel

I'm still towing with my 2004 Titan. Current trailer goes across the scale just over 6,000 #. Current Odometer reading is ~112,000 and it pretty much ONLY tows.

I pretty much just use the brakes for the final couple hundred feet of stopping and only as needed to keep RPM's down when descending steep grades (hard brake to lower RPM then off and let cool). Brakes were replaced as part of a "campaign" by Nissan back somewhere around the 50k mark and were inspected by the Dealer a couple weeks ago. Still in the "Good" category after all those miles of towing.

Truth be told, diesel engines without compression brakes do not provide any "engine braking". Here's an explanation:

Diesel engines. Diesel engines do not have engine braking in the above sense. ... Since they do not maintain a throttle vacuum, they are not subjected to the same engine braking effects. This is partly why non-turbo diesel-engined vehicles can coast in-gear for longer than an equivalent gasoline engine.

[JPin AZ]

Engine braking, no mater what type of engine, relies on transmission gear ratio to occur. Jake brakes are a completely different thing and one of a diesels biggest benefits. You can not compare a jake brake to gas.

[Greg in michigan]

Originally Posted by TitanMike

I'm still towing with my 2004 Titan. Current trailer goes across the scale just over 6,000 #. Current Odometer reading is ~112,000 and it pretty much ONLY tows.

I pretty much just use the brakes for the final couple hundred feet of stopping and only as needed to keep RPM's down when descending steep grades (hard brake to lower RPM then off and let cool). Brakes were replaced as part of a "campaign" by Nissan back somewhere around the 50k mark and were inspected by the Dealer a couple weeks ago. Still in the "Good" category after all those miles of towing.

Truth be told, diesel engines without compression brakes do not provide any "engine braking". Here's an explanation:

I not saying my diesel titen has engine braking, maybe some type of transmission braking????
All I know is with toe mode off it stoppes like my old titan. With toe mode on when I press the brake and it down shifts it feels like someone grabbed the tt rear bumper and gave it a yank.

[TitanMike]

Originally Posted by JPin AZ

Engine braking, no mater what type of engine, relies on transmission gear ratio to occur. Jake brakes are a completely different thing and one of a diesels biggest benefits. You can not compare a jake brake to gas.

Very true. When using a lower gear the the ratio is reversed, requiring more torque on the output shaft to spin up the engine. In some circles it's referred to as 'gear pressure'


If you compare a diesel (w/o compression brake) to a gas engine, the gas engine requires more torque to spin it up with a closed throttle than a similar sized diesel with throttle lifted. Thus tranny's being equal, final drive ratios being equal, engine displacement being equal, the gas engine equipped vehicle will slow quicker with closed throttle than the diesel.


Greg in michigan---

Nissan is using in their Diesel Titan a modern version of the old Allison "Retarder" system in their transmission. Back in the 50's and 60's large gasoline powered trucks with the Allison transmission were equipped with a "fourth pedal" (to the left of the clutch as I recall) that could be pressed and it used hydraulic pressure to reduce speed (or so it was explained at the time). Today's version is now integrated into the PCM which controls shifting etc.

FWIW I looked at a 2019 Nissan Titan about a month ago. For $40k, plus my 2004 I decided to just "ride this old horse until she quits".