Is it bad to use the transmission to decelerate

[Sherman Bird]

I guess I do not understand the inner workings of the transmission

But I am pretty sure if you read the owners manual it will describe that 2 and 1 are to be used for going downhill and for increased power uphill

Even the manual in my 1987 dodge Aries Station Wagon says to use 2 and 1 this way.

The RFE transmission definitely will downshift to hold speed. And with tow haul mode on the transmission actually can read if you are going uphill or downhill.

I would use the transmission to engine brake and to go up the hill in the power.

But I am not a mechanic or an engineer. So take my thoughts with a grain of salt.

It is proper instruction to select a gear one gear lower than you would use to go up to go down a grade.

And you should do this at the top.

If your RPMs are in range...exactly like you would decide with a manual...i would downshift.

And going up the hill, it will keep the transmission from upshifting when you release the gas for a turn etc. And keep the transmission from hunting.

My opinion

If you are accelerating (going uphill) The Computer commands an increase of line pressure, changes the algorithm of TV/Governor pressures because of the increased APP (Accelerator Pedal Position) signal that, with road speed inputs tell the TCM (Transmission Control Module) what extra load is put on the drive line and changes the behavior of the transmission.

When you are going downhill, you are typically at minimum throttle. The TCM sees the minimum APP input and will reduce line pressure. The manual gear selection tells the PCM that you chose this gear and will inhibit any further upshift beyond what ever gear you chose.

 

[Narg]

Arguably, it's better on the vehicle as a whole. Heck, even the cruise control in the newer models downshift automatically as needed on the highway to keep speed constant.

 

[Sherman Bird]

Arguably, it's better on the vehicle as a whole.

What is "IT"?

 

[Marshall]

Well, I won't be dropping it into 2nd anymore while towing. I don't do it often and when I do. It's for short intervals. But I'm curious because. I have a 2017 F250 work truck, when I'm pulling heavy loads with that. It will downshift into 3rd and sometimes 2nd by itself. If you start slowing down on steep grades. But of course, it's a complete different transmission. But yeah, now I learned that's not good to do, while towing or loaded down. Ok, what about going up hill ? Dropping it into 2nd gear? Will that eventually kill a transmission? I have to favor 2nd gear a alot up hills with my 35x12.5x20 rims, and 3.55 gearing. Thats my reasoning to why I need to favor 2nd. What are the consequences of constantly doing this?

If you are having to pull up in 2 nd gear, you are geared wrong, but pulling should be fine, going down hill is where things can get hairy my 14 8 sp will stay at 50Km in town down most hills , but that is the computer doing that, which you don't have. I don't think pulling it into 1 or 2 nd is a good idea , unless you are in your yard.

 

[RoadRamblerNJ]

Do what I did...push it hard enough to break it while it's still under warranty, lol.

 

[ramffml]

I'd really suggest you read the OWNER'S manual! Re-read what I wrote . I said that using the transmission manual range is likely OK when the truck is unloaded, but when the manual braking is used with a heavy load, maybe not such a good idea and I stated why.
BUT, These NEW models may have been upgraded where the use of the transmission to provide a surrogate braking would be OK. I would not do that. I'd use the brakes and IF I HAD to use the transmission, I'd certainly try my best to let the brakes handle the lion's share of the load and be very cautious about using the trans.

BTW.... the old school trans controls said "OVERDRIVE OFF" when that button was pushed. Since so few people really read the owner's manual, which said to select that in the event of towing, manufacturers had to make it more plain and simple!

Ok, if you're making a distinction between using manual mode vs auto mode, possibly you are correct there because you might be holding it into a lower gear than computer otherwise would. But again, if the truck was explicity designed to act as an engine brake (which, at least these 2019's are), then I don't see how that can be damaging to let the engine rev to 3000+ while going down hill with a load, when the transmission is in auto mode.

Even with tow haul off, as soon as you go down a hill, the computer triggers a downshift automatically for you to apply engine braking. This is a feature by design, you can start at top of hill, coast down, but as soon as brakes are applied the computer drops you down a gear and holds the revs until you are flat again for a few seconds or until you apply throttle. By design. You cannot prevent this behaviour or turn it off even if you wanted to. These trucks just rev high going down hills and nothing you can do can prevent that.

With tow haul engaged it is even more eager to downshift.

So I don't see why Ram would add such a feature if it is harmful to the transmission.

 

[Snake15eyes1998]

If you are having to pull up in 2 nd gear, you are geared wrong, but pulling should be fine, going down hill is where things can get hairy my 14 8 sp will stay at 50Km in town down most hills , but that is the computer doing that, which you don't have. I don't think pulling it into 1 or 2 nd is a good idea , unless you are in your yard.

I am geared wrong, I have 3.55 gears with 35x12.5x20s. But I dont wanna spend the $3000 i was quoted to regear. That's for a different thread, but $3000 can buy a lot of diapers and wipes hahaha. I'll probably end up just driving it the way it is, then buy a bigger truck down the road

 

[APPsBeast]

Breaks are cheaper to replace then a transmission

 

[bm02tj]

We know the IT guys or gals at FCA are not the brightest but there is no way they would lower the band pressure to the point they will slip in a lower gear
use the transmission and not the brakes as much
Unless someone can produce anything other wise use the gears

 

[MoPowered]

Boy oh boy, it just isn’t that hard to understand, this is what happens with too much tech, spend all day on their cell phones, pc’s and smart tv’s and they get technology smart and practical application dense!
“IT” used to be known as book smart vs. street smart.
Welcome to our future!

 

[Mikes578514]

I do it almost all the time towing or not coming to a stop sign, slowing for a turn, 1 Or 2 gears at a tiMe

I have a 2007 1500 5.7 545-rfe I was wondering if its bad to downshift to 1st or 2nd when going down a hill or is that bad for the trans?

Sent from my SM-N975U1 using Tapatalk

 

[ramffml]

Boy oh boy, it just isn’t that hard to understand, this is what happens with too much tech, spend all day on their cell phones, pc’s and smart tv’s and they get technology smart and practical application dense!
“IT” used to be known as book smart vs. street smart.
Welcome to our future!

Maybe it's because I spend too much time in IT, but I'm having a hard time figuring out what you're trying to say. What, exactly, "isn't that hard to understand"? Using the transmission or not to brake down a hill?

 

[Tim Garceau]

Interesting flex, but having the greatest 8 speed transmission of all time along with ERS the only time I honestly use the brakes is when coming to a sudden or complete stop.


If the buttons wear out I’m going paddle shifters.

 

[DieselMike29]

You do realize that it is ENGINE COMPRESSION that you are using to slow your vehicle when you shift into a "lower" gear, don't you?

Having said that, it is neither good nor bad for your transmission to use ENGINE COMPRESSION to slow your vehicle; what IS bad is HOW your force the transmission to be in that lower gear. With a manual transmission you are in either neutral (no gears meshed) or the gear ratio you have MANUALLY selected - either or, NO IN-BETWEEN. If you are doing 70 MPH and select second gear, you most likely will cause the transmission to come apart (Ask Big Daddy Don Garlits about that and why Top Fuel Dragsters are no longer "slingshots") [He blew a transmission that was inches from his ankles and nearly amputated his right? foot when the transmission on his "slingshot" top fueler exploded.]

A AUTOMATIC transmission on the other hand is in a pump and valves which the transmission selects to provide the best power to torque ratio for the job being required. When you (the driver) select a lower gear, the transmission determines how best to get into that "gear" (actually "reduction ratio") and essentially slows the vehicle down while changing gears to get to where you want it to be.

The question use to be "What happens when you shift from top gear on a manual transmission at (call it) 50 MPH into reverse?" The correct answer was "you end up with your transmission or rear end or both on the highway behind you." With an automatic, (if the shift mechanism allows you to actually move it into R from D (think pushbutton transmissions in Chrysler Motor company vehicles (Yes, my 1961 Plymouth had one) (and the Ford Edsel)) you will gently roll to a stop and then the transmission will actually shift into reverse!

 

[crash68]

The question use to be "What happens when you shift from top gear on a manual transmission at (call it) 50 MPH into reverse?" The correct answer was "you end up with your transmission or rear end or both on the highway behind you."

With the 8HP line of transmissions (and just about every electronically shifted transmission) you get a warning on the dash to shift back to drive. The transmissions nowadays are smart, they won't even let you shift into a gear that too far out of rpm range.

 

[Tim Garceau]

Yeah I pop in over to R for the reverse camera often on the highway if something needs a second look.

Logic is wonderful isn’t it. Just like the TCM knowing it can’t feasibly switch into a lower gear without exceeding the programmed PCM rev limit. The Germans have magic powers but let’s get back to the old timers and their RFE

 

[Mitch1204]

First off disc brakes don't fade like drum brakes. They get hot and glaze your rotors. If your rotors look shiny your brakes have been hot a time or too. Not an alarming issue but braking is just a little bit diminished with shiny rotors. Upgrade to slotted rotors if you do alot of hauling in the hills. They stay cooler.

Downshifting is not an issue if done correctly. The trick is not to over tach. You don't want to be doing 70mph and slam it into 2nd. Slow down to the appropriate speed then downshift. Your owners manual should explain the speed range of each gear.

 

[Neil E]

when going down a 6 percent grade on my commute, I just set the cruise at 55 and let the truck downshift as it needs to. It maintains a speed of 54 to 59 mph. I figure that is better than riding the brakes like most others.

 

[MoPowered]

Maybe it's because I spend too much time in IT, but I'm having a hard time figuring out what you're trying to say. What, exactly, "isn't that hard to understand"? Using the transmission or not to brake down a hill?

What I was referring to and what I think all of us are trying tell the OP, is that using the transmission to either down shift, up shift, while towing or not towing for that matter, isn’t that hard to understand “IT” not I.T., what gears he has and tire sizes and engine braking yada, yada, yada, use your head for other than a place to park your hat. If your driving your truck uphill, downhill, towing, not towing, using your transmission to downshift/upshift or and hear the engine scream with rpm’s shooting up or a power loss by too high a gear, using your brakes and starting to build excess heat because the load is too heavy etc.... change what your doing in that moment plain and simple. That is what “IT” was that I was referring to.

 

[Kukailimoku]

In large commercial truck (or airliners) it is a no brainier to use engines to assist in deceleration because the brakes can actually fade.

In a consumer grade vehicle. Nah.

So what of your brakes take more wear and tear than if you used the engine to help slow down?
Aren't the brakes consumable anyway????


This debate is equivalent to asking:
"Should one shorten the lifespan of a permanent part in order to prolong the life of an expendable part?"

If I had a nickel for every time I saw someone spend $200 to save $2....

As far as actual brake fade in a consumer vehicle?
Yeah, I had it happen only ONCE to me and I'm 53 years old. I was coming down Mauna Loa on Hawaii Island. That is a descent of what, 13,700' to about 7-8,000' in a timespan of about 15(?) minutes. Yeah, I experienced true brake fade in a consumer grade car. Had to use the handbrake and downshift disturbingly harshly. But that was in a cheap tiny rental. I have since gone down that mountain on more substantial vehicles and at a more realistic pace, and brake fade never even came close.

So NO, do not use the engine to decelerate.

After I got my first pilot's license I started to drive as if I fly.
The two are different activities and not interchangeable. Had to give that up and go back to plain old driving, and not "flying a car on a road."
So don't drive your one ton car-witha-cargo-bed as if you were driving a Peterbilt pulling a full load...