Downshifting

Petersb · 03-06-2016, 11:16 PM

Any one with the Mercedes do you downshift when driving down a steep grade or going up a steep grade. Good idea or better to let trans work for itself.

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Sandiegodoug · 03-06-2016, 11:35 PM

I downshift going down, especially if towing my jeep and going down a steep grade . Don't shift up, tranny seems to do ok at that, but going down it will shift to top gear unless I downshift

CaptnJohn · 03-06-2016, 11:36 PM

I drop from auto to manual 5th gear, make sure the engine brake is on, set the cruise control, and tap the trailer brake if needed. Only 1 grade at 7% for 7 miles is all that needed.

MarsMan · 03-07-2016, 06:07 AM

I sure do. I have a gauge and I can see when the load on the engine is high and requires a downshift while going up a grade. I find the tranny does not downshift in time so I help it. I think it helps with my fuel economy. I do not normally downshift going down a grade unless it is steep

Mikegjax · 03-07-2016, 08:06 AM

Shift up or down depending grade. Recommended in operators manual.

CharSolera · 03-07-2016, 09:52 AM

I absolutely downshift for steep grades. Much better option than braking to slow down on decent. To downshift the MBS, simply bump the shift lever to the right. The gear you're in shows on the control panel. Watch the engine speed -- you still need to use the brakes on steep downhills.

namusmc · 03-07-2016, 01:35 PM

Also, engine braking prolongs the life of brake pads and rotors.

Phinias · 03-07-2016, 05:52 PM

i try to keep it over 2K no matter what. not a good idea to lug it no matter what the circumstance

CaptnJohn · 03-07-2016, 07:47 PM

Quote:

Originally Posted by Phinias

i try to keep it over 2K no matter what. not a good idea to lug it no matter what the circumstance

I'll have to watch the down hill RPM as a 35' 5er weighing about 11,000# going 65 MPH is only around 1700 RPM.

gfarmcafe · 03-07-2016, 07:59 PM

Quote:

Originally Posted by CharSolera

I absolutely downshift for steep grades. Much better option than braking to slow down on decent. To downshift the MBS, simply bump the shift lever to the right. The gear you're in shows on the control panel. Watch the engine speed -- you still need to use the brakes on steep downhills.

I agree. A good rule is to descend in the same gear as you use going up the grade. Pump the brakes lightly, if needed, so you don't overheat them.

**RedLdr1** · 03-08-2016, 10:28 AM

I definitely down shift going up steep inclines as the transmission is a bit too optimistic on how long to stay in top gear. When descending I downshift if it feels like I need to or it is a steep grade. If there is a sign warning trucks about a grade and to down shift I generally follow the advise...

Still Kickin · 03-08-2016, 09:20 PM

Quote:

Originally Posted by Mikegjax

Shift up or down depending grade. Recommended in operators manual.

Absolutely X 2

MNtraveler · 03-09-2016, 01:28 AM

Seems the cruise control will downshift for you to control speed down hills. But I haven't tried it on any large hills or mountains yet.

Land of 10,000 Lakes
2016 Forester MBS 2401R

MNtraveler · 03-10-2016, 02:01 AM

As the AT will downshift when it needs for the most part, one of the main reasons for downshifting manually when going up hills is to stop gear "hunting" whereby the AT downshifts, brings you back to speed then upshifts, then you slow down with loss of engine power and it downshifts, and on and on. In addition to being quite annoying, this can overheat and damage the AT. Downshifting manually puts it where it needs to be and keeps it there for the duration. You then set and control the speed and keep it right there.

Land of 10,000 Lakes
2016 Forester MBS 2401R

MNtraveler · 03-10-2016, 02:10 AM

A very good article on this topic:

https://www.fmca.com/motorhome/motor...-the-work.html

Land of 10,000 Lakes
2016 Forester MBS 2401R

bob dirt · 03-10-2016, 11:35 AM

Good article. Always scared of running the R's that high but it makes sense

MNtraveler · 03-15-2016, 09:25 PM

Quote:

Originally Posted by bob dirt

Good article. Always scared of running the R's that high but it makes sense

Anyone have an opinion on how many revs are too many for the MBS engine?

(Need I even ask if anyone has an opinion?!)

OldCoot · 03-15-2016, 09:59 PM

Quote:

Originally Posted by namusmc

Also, engine braking prolongs the life of brake pads and rotors.

As long as it doesn't over rev the engine. Brake pads & rotors are cheaper than rods, brgs & crankshafts. I limit my old Chevy to 3600 rpm up hill and down hill I use the brakes intermittently.

Mikegjax · 03-16-2016, 03:39 PM

Quote:

Originally Posted by MNtraveler

Anyone have an opinion on how many revs are too many for the MBS engine?

(Need I even ask if anyone has an opinion?!)

I remember reading somewhere (don't ask where) that the computer will not let you over rev the engine.

MNtraveler · 03-16-2016, 03:55 PM

Quote:

Originally Posted by Mikegjax

I remember reading somewhere (don't ask where) that the computer will not let you over rev the engine.

Interesting. I can see how it would do it uphill (throttle limit), but now sure how it would do it downhill when it's driven by gravity - unless it disconnects the tranny. Well, maybe it just upshifts (duh!) and you are on your own with the brakes at that point until you bring it back down to a reasonable speed (which is what one should be doing anyway).

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