Engine/transmission braking in gas engines

Engine braking works with any gas engine and automatic (or manual transmission, not a RV option). Options like Ford's tow-haul and Allison's grade retard automate the process a little, but you still need to understand what you are doing, e.g. engine braking is proportional to RPM and works only with throttle closed.

Everything I have other than the RV is manual transmission, about 1/3 of my braking is by engine. Most modern car automatics will do almost as much, no effort on your part, if you drive reasonably, get off the gas early as possible when there is a stop or slowdown ahead. Hybrid fuel savings depend on the driver learning this.

Thanks for all the good information. The trani brakes are a great feature that I would happily use if on my rig. I was starting to use that as a major criteria for buying a coach. But if I can accomplish the same thing manually as I have for several yrs with my pickup towing a TT, I will bump this down to a secondary criteria. I was not sure if the engineers had done some funny business with the gas engine also to help with braking.
Thanks again

bhildreth wrote:
Thanks for all the good information. The trani brakes are a great feature that I would happily use if on my rig. I was starting to use that as a major criteria for buying a coach. But if I can accomplish the same thing manually as I have for several yrs with my pickup towing a TT, I will bump this down to a secondary criteria. I was not sure if the engineers had done some funny business with the gas engine also to help with braking.
Thanks again

Yup, the tow/haul is not a big advantage if you can shift yourself. On the other hand, the extra gear and 50 hp in the 2006 and newer Fords are nice things. However, I've gotten along fine with my older V10 and 4 speed.

Ivylog wrote:
If the nut behind the wheel cannot reach up and pull the lever down or back up then I guess the tow/haul is a good thing. Any gas engine does a good job of braking but you have to take your foot off the gas and manually down shift to get the rpms up.

The difference being that the computer does some decision-making before shifting: it doesn't take it very long to ask itself "If I downshift now will it cause the engine to over-rev at all?" The nut behind the wheel can also ask himself the same question, but then he has to know the current road speed, gear ratio, and engine speed so he can calculate what the resulting engine speed will be after the down-shift, then decide if that engine speed is within the safe operating range of the engine and reach up and make the shift. He can also over-ride his calculation and say to himself "I don't care what my calculation says - I know my engine has a built-in safety factor and it will be okay". It's also a lot easier to simply put your foot on the brake pedal momentarily rather than to fiddle with the shift lever to make sure you only shift down one gear - or shift back up a gear without pulling it all the way up into Neutral...

The Allison programming makes it impossible for the drive train to be damaged by a shift - it simply won't shift unless it can be done safely.

My first tow/haul option was on a 2005 F350 diesel that I pulled a big Montana all over the country with. I had previously owned a 2002 F350D without tow/haul. I found it to be a very handy convenience going across the Rockies and even on some of the much shorter but still steep grades on the Blue Ridge. It also comes in handy when exiting an Interstate exit ramp. I am happy to have it on my 2012 gasser too. On long down grades one tap = one gear. The really steep grades usually take two taps and then I seldom have to use the brakes. Its a good system and very easy to use without having to use the shift lever. You can focus on the road ahead without distraction.

Alan_Hepburn wrote:

Ivylog wrote:
If the nut behind the wheel cannot reach up and pull the lever down or back up then I guess the tow/haul is a good thing. Any gas engine does a good job of braking but you have to take your foot off the gas and manually down shift to get the rpms up.

The difference being that the computer does some decision-making before shifting: it doesn't take it very long to ask itself "If I downshift now will it cause the engine to over-rev at all?" The nut behind the wheel can also ask himself the same question, but then he has to know the current road speed, gear ratio, and engine speed so he can calculate what the resulting engine speed will be after the down-shift, then decide if that engine speed is within the safe operating range of the engine and reach up and make the shift. He can also over-ride his calculation and say to himself "I don't care what my calculation says - I know my engine has a built-in safety factor and it will be okay". It's also a lot easier to simply put your foot on the brake pedal momentarily rather than to fiddle with the shift lever to make sure you only shift down one gear - or shift back up a gear without pulling it all the way up into Neutral...

The Allison programming makes it impossible for the drive train to be damaged by a shift - it simply won't shift unless it can be done safely.

True however, one should downshift into the gear before starting down the grade to avoid an over rev scenario, although most modern transmissions won't let you downshift anyway if it will cause an over-rev. I read once that a good rule of thumb is use whatever gear it takes to get up the hill, as your gear coming back down. Granted, you would of had to come up the grade at some point to know what that is :)