Using manual downshifts on hills - Diesel Truck Forum - TheDieselGarage.com
Thread Details Posted by densell, this thread has received 9 replies and been viewed 2369 times.

 
LinkBack Thread Tools Display Modes
post #1 of 10 (permalink) Old 07-07-2011, 04:50 PM Thread Starter
Junior Member
 
Join Date: Oct 2010
Location: Canada
Posts: 25
Points: 24,878
Thanks: 1
Thanked 2 Times in 2 Posts
Using manual downshifts on hills

During my commute to work there are several hills with traffic lights at the bottom of them, some have stop signs. When I'm at the crest of the hill, I use the manual downshift button to drop into 5th, then as I come down the hill I generally use it to run down into 4th, 3rd, and 2nd. I find this adds some good engine braking, so that my use of the truck breaks are limited. As I run this route daily, I'm sure over time it will increase the life of my breaks.

I have 2 questions (perhaps some of you guys with good mechanical knowledge can answer). First, by doing this, am I putting undo wear and tear on the transmission and engine - thus, negating the gains I'm getting from not using the brakes ?

Second, would just hitting the tow/haul button at the creast of the hill be better. That would allow the transmission to decide how to apply the engine brake.

Any feedback or comments are welcome.

Thanks in adavance.
densell is offline  
Sponsored Links
Advertisement
 
post #2 of 10 (permalink) Old 07-13-2011, 12:21 PM
Junior Member
 
Join Date: Jul 2011
Posts: 4
Points: 14,604
Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by densell View Post
During my commute to work there are several hills with traffic lights at the bottom of them, some have stop signs. When I'm at the crest of the hill, I use the manual downshift button to drop into 5th, then as I come down the hill I generally use it to run down into 4th, 3rd, and 2nd. I find this adds some good engine braking, so that my use of the truck breaks are limited. As I run this route daily, I'm sure over time it will increase the life of my breaks.

I have 2 questions (perhaps some of you guys with good mechanical knowledge can answer). First, by doing this, am I putting undo wear and tear on the transmission and engine - thus, negating the gains I'm getting from not using the brakes ?

Second, would just hitting the tow/haul button at the creast of the hill be better. That would allow the transmission to decide how to apply the engine brake.

Any feedback or comments are welcome.

Thanks in adavance.
I do similar things when driving with mine, when I am driving through the mountains I just leave it in Tow/Haul. Touching and releasing the brake pedal going downhill will cause a downshift, do it again and it will downshift again. To me this is easier than constantly hitting the paddle.
post #3 of 10 (permalink) Old 07-13-2011, 01:45 PM
Senior Member
 
Join Date: Dec 2008
Location: e.texas
Posts: 590
Points: 42,580
Thanks: 8
Thanked 63 Times in 52 Posts
My thought on this, as mentioned use tow haul. In the end, i would prefer to replace a set of pads, then i would a tranny.
navistar45 is offline  
post #4 of 10 (permalink) Old 07-14-2011, 04:28 AM
Junior Member
 
Join Date: Dec 2008
Posts: 4
Points: 64
Thanks: 0
Thanked 1 Time in 1 Post
I'm still waiting for a mechanical expert to respond, but in the meantime here's my logic:

I don't think there's any added mechanical stress the drive train is not designed to handle.

Most of the engine wear and tear is caused by friction. So I presume higher RPM's equals more friction on anything that rubs (valves, rings, pistons, etc).

However, engine braking super cools the engine and pumps a lot of lubricating oil through the system, which may reduce the friction and wear effect.

Brake pads might not be the only thing need replacing, but could be warped rotors and calibers too.

I think the key to engine mechanical longevity is to keep those RPM's low (assuming you're doing everything else the manufacturer recommends).

But in the end, not too many people keep their vehicle until its dead. Better to trade it or sell it before it is too old to get rid of.

Jake
snakyjake is offline  
post #5 of 10 (permalink) Old 07-14-2011, 12:08 PM
Senior Member
 
Join Date: Dec 2008
Location: e.texas
Posts: 590
Points: 42,580
Thanks: 8
Thanked 63 Times in 52 Posts
I cant see engine wear being an issue, unless the shift is at high rpms. The wear will be in the shifter, and the tranny itself.. More shifting, equates to more wear.. Likewise, more brake use equals more friction, meaning more wear.. There is no way around the wear factor, it's just the cheapest and easiest to repair, is the brakes..
navistar45 is offline  
post #6 of 10 (permalink) Old 07-14-2011, 04:28 PM
Member
 
Join Date: Nov 2006
Posts: 139
Points: 33,582
Thanks: 0
Thanked 4 Times in 4 Posts
The autosequential shift mechanism doesn't allow you to down shift to early and damage anything so I would think the engineers designed that specifically to prevent premature wear or failure.

I use the column shifter to downshift over the tow haul when empty becuase I don't like the pattern of shifting when I'm not towing. It is a little jerky and on gravel/snow it will cause the tires to break free sometimes.

No true mechanical knowledge for you and I will trade out the truck in two years so I'm not looking at long term effects. Mine will go down the road with 60,000 miles or so then I don't worry about brake pads, front end work etc.
06kma is offline  
post #7 of 10 (permalink) Old 07-15-2011, 04:39 AM
Junior Member
 
Join Date: Dec 2008
Posts: 4
Points: 64
Thanks: 0
Thanked 1 Time in 1 Post
Quote:
Originally Posted by navistar45 View Post
I cant see engine wear being an issue...
You don't think running the engine at higher RPM's creates more engine wear?
More RPM's equals more piston shear against a cylinder. More camshaft revolutions, more valve seats, more bearing movments. It's more of everything.

Typically the engine creates compression to power the vehicle weight. This is the reverse case; decompression is created to decelerate the vehicle weight.

Anytime a mechanical device is doing work, it's wearing...otherwise it wouldn't be work.
snakyjake is offline  
post #8 of 10 (permalink) Old 07-15-2011, 12:28 PM Thread Starter
Junior Member
Threadstarter
 
Join Date: Oct 2010
Location: Canada
Posts: 25
Points: 24,878
Thanks: 1
Thanked 2 Times in 2 Posts
Thanks for all of the replies. Seems using the the manual downshift and/or the tow haul might not be the way to go. I get the impression that the wear and tear on the engine out weighs the benefit of the savings on the brakes.
Seems Ford need to develop a system like they have in Hybird vehicles whereby engine braking recharges the batteries. It just is such a waste of energy when you consider the mass of the truck and the force required to bring it to a stop everytime we brake.
densell is offline  
post #9 of 10 (permalink) Old 07-15-2011, 01:47 PM
Senior Member
 
Join Date: Dec 2008
Location: e.texas
Posts: 590
Points: 42,580
Thanks: 8
Thanked 63 Times in 52 Posts
Quote:
Originally Posted by snakyjake View Post
You don't think running the engine at higher RPM's creates more engine wear?
More RPM's equals more piston shear against a cylinder. More camshaft revolutions, more valve seats, more bearing movments. It's more of everything.

Typically the engine creates compression to power the vehicle weight. This is the reverse case; decompression is created to decelerate the vehicle weight.

Anytime a mechanical device is doing work, it's wearing...otherwise it wouldn't be work.
Sure it will, thats logic. But look at it like this when it comes to the tranny.. Which do you think will last longer, the tranny in a bus going up and down the highway, or that same bus doing street corner to corner stop and starts? When i do a manual down shift in my 11', my switch to do the down shift gets wear, the tranny gets to often make a rougher downshift how ever many time i decide to press the button, the driveline gets a bit of shock from the down shifting, the engine rpms climb higher,and then the brakes get used as well.. If you let tow mode do some of this work, the so called engine brake will aid and everything becomes a bit less worked/used, depending on speed and load.. I'am not saying a manual down shift isnt ever called for, but as the orig poster decribed, i cant see any need in it ..
navistar45 is offline  
post #10 of 10 (permalink) Old 07-19-2011, 02:43 PM
Tebow-in'...
 
mudguppy's Avatar
 
Join Date: Dec 2008
Location: duncan, SC
Posts: 1,243
Points: 32,335
Thanks: 173
Thanked 142 Times in 105 Posts
Quote:
Originally Posted by densell View Post
... Seems Ford need to develop a system like they have in Hybird vehicles whereby engine braking recharges the batteries. It just is such a waste of energy when you consider the mass of the truck and the force required to bring it to a stop everytime we brake.
they did in '02, although it was a system that accumulated, stored, and released mechanical energy to assist with braking/starting to improve fuel economy. it was a high-pressure gas accumulator tied into the rear driveline; it would use the truck's driveline energy during braking to compress gas in one tank and release it back through the driveline into another tank for take-off.

not sure why they didn't go forward with it.

Travis
---------------------------------------------------
2011 F350 SRW CC/SB 4x4 Lariat 6.7 PSD Dark Pearl Metalic

1974 Bob'd Deuce on 16.00-20 XZLs, locked front and rear, hydro steering, front and rear winches, 5.9CTD/nv4500, hydro-boosted disc brakes

Member since Jul 05, Dually Club Member #63, American Club Member #42, FOSP Member #8
mudguppy is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Diesel Truck Forum - TheDieselGarage.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Similar Threads
Thread Thread Starter Forum Replies Last Post
Smoking on the hills Bigfoot is real 7.3L and 6.9 IDI (Pre 1994) 1 06-24-2010 05:48 AM
Proper way to pull hills? Need quik answer?? zgoo Medium and Heavy Duty 4 12-22-2009 04:57 AM
F350 + GMC Brigader + Icy hills = A LITTLE FUN! STANG302 Towing and Hauling 7 01-17-2009 01:06 AM
truck surges going up hills tru_camaro 5.9L Cummins (2003-2007.5) 5 09-22-2007 08:23 PM
Howdy... From The Hills Of Tennessee! GREASEL-MAN Introductions 18 09-16-2007 01:09 AM

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome