I have a 2004 Coachmen Sportscoach with a 330hp CAT, and 6-speed Allison transmission. Here is my question. Do I risk damaging my transmission if I down-shift in order to slowdown or to save on my brakes when going down a long and/or steep grade? In reading through all my manuals I cannot determine if my coach is equipped with a jake brake.

The Allison transmissions I am familiar with will not allow you to downshift if the RPMS are too high. It has it's own computer to prevent damage.If you try to downshift at too high RPms the tranny will not shift.

Most transmissions will protect themselves, so you'll need to use both brakes and transmission. Get RPMs down to the lowest gear that will allow control, then use brakes to help drop RPMs. Don't ride the brakes (or do your best not to). Work your way down until you get to your desirable speed. Use lower gears as much as possible.

Research exhaust brakes, not jake for your engine.

Jake Brake is a name of a product from Jacobs Vehicles and works with your valve train.You probably have an exhaust brake and its usually labeled engine braked. Mine is by my left hand on the side console with other switches.As mentioned, the Allison trans wont downshift it means over revving your motor.

Paul1944 wrote: Do I risk damaging my transmission if I down-shift in order to slowdown or to save on my brakes when going down a long and/or steep grade? Absolutely no problem......IF you anticipate the downhill and down shift BEFORE your speed gets out of control, like at the crest of the hill right after the grade warning sign.And that applies equally no matter what engine and transmission you have.The truckers rule of thumb is:Whatever gear you had to use to pull UP the hill, is the same one you should use going down the other side.

Risk of down-shifting? | Good Sam Community

23 Replies

TomG2
Explorer
Aug 11, 2017
I guess I am showing my age. Habitually downshifting the old Powerglides, Hydramatics, and Ford-O-Matics to slow down was harmful. Modern transmissions are a huge improvement over those old slushboxes. It is probably better to slow down a little before extra braking is needed anyway. In an emergency, I would put one in reverse if I thought it would help.
DiploStrat
Explorer
Aug 10, 2017
hornet28 wrote:
Hard to guess what those of you who claim to have wrecked trannies and clutches did wrong downshifting. But I've been doing it since 1960 on sticks and autos and have never wrecked or blown any. If you want to depend on brakes only for steep downgrades have at it. If on an expressway or where they have runaway ramps keep your eye out for where they are. Also get a plan for what are you going to tell passengers about the smell of cooking brakes, the smoke exiting the rear or the "Oh SH%T" moment when you realize your brakes are gone

Amen!
hornet28
Explorer
Aug 10, 2017
Hard to guess what those of you who claim to have wrecked trannies and clutches did wrong downshifting. But I've been doing it since 1960 on sticks and autos and have never wrecked or blown any. If you want to depend on brakes only for steep downgrades have at it. If on an expressway or where they have runaway ramps keep your eye out for where they are. Also get a plan for what are you going to tell passengers about the smell of cooking brakes, the smoke exiting the rear or the "Oh SH%T" moment when you realize your brakes are gone
TomG2
Explorer
Aug 10, 2017
WNYBob wrote:
I agree, with using both, but I was told once, ask yourself a question which cost more to fix. So I use my breaks more than the trany.

Learned that the hard way. Brakes are way cheaper.
DiploStrat
Explorer
Aug 10, 2017
ryegatevt wrote:
... on an overloaded 1960 Morris Minor Sedan, … DOWNSHIFT!!!

Ah, a gentle person of my own generation!

N.B. Putting anyone in a Morris Minor constitutes overload!

But the advice is still correct - Downshift on those grades! Especially with an automatic, and, if rock crawling in a 4x4, shift to low range earlier with an automatic - there is less engine braking.
ryegatevt
Explorer II
Aug 10, 2017
I have been downshifting vehicles since 1955 - sports cars, sedans, trucks, RVs - you name it - manual and automatic transmissions, and have never burned out a clutch or blown a transmission. I completely faded the brakes only once, on an overloaded 1960 Morris Minor Sedan, but they quickly cooled down and recovered. DOWNSHIFT!!!
LandYachtReviva
Explorer
Aug 10, 2017
I put over 100,000 miles on a 2004 40' Fleetwood Revolution with exhaust brake and Allison 6 speed.

I always manually downshifted to 4th or lower on a steep downgrade 5% or more.

No issues.
wa8yxm
Explorer III
Aug 10, 2017
12th Man Fan wrote:
The Allison transmissions I am familiar with will not allow you to downshift if the RPMS are too high. It has it's own computer to prevent damage.

If you try to downshift at too high RPms the tranny will not shift.

Ditto. On fact the Allison on gas RV's has a feature called Grade brake.. That is what it does.. You Engate the brakes (I usually have to do it twice) and it will downshift if it can.. If the grade is enough that you still pick up speed it will upshift when the RPMs get too high ... A very smart transmission.
wnjj
Explorer II
Aug 09, 2017
WNYBob wrote:
I agree, with using both, but I was told once, ask yourself a question which cost more to fix. So I use my breaks more than the trany.

This is valid advice for people who (over)use the transmission while slowing to make a turn or come to a stop, not for descending grades.
DiploStrat
Explorer
Aug 09, 2017
Manual or automatic, you descend downgrades on the gears, not the brakes. If you downshift properly it places no extra strain on the transmission.

While brakes may be cheaper than clutch plates, I doubt that many of the folks posting here still have a manual transmission. More to the point, however, brakes can overheat and fail on long downgrades.

Descend in a gear that is low enough to hold your vehicle at the desired speed without using your brakes. With a diesel, use your exhaust brake if available.