Risk of down-shifting?

[Paul1944]

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.

[TomG2]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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.

[sch911]

If you have an exhaust brake there would be a separate switch included to turn it on and off. You do not have a Jake brake that's a little different. If you do have an exhaust brake just turn it on and the trans will automatically downshift on its own.

[Tiger4x4RV]

My 2006 Allison 6-speed has a tow/haul mode. If you click into that at the top of a downhill, it will set the speed at which you clicked and will pretty much maintain that speed until you touch the brake pedal or the gas. This works best for me on long freeway downhills.

For narrow winding mountain downhills, I use the tap-shift mode. It sets the highest gear you will allow the transmission to use, which does help in slowing things down. You can downshift with it, but should you?

[Lynnmor]

Cranemec wrote:
Same gear down as same gear up. Downshift before you start down the hill.

That is rather dated, newer turbocharged diesels with high horsepower and low end torque might top the mountain in one of the highest gears, but need a lower gear to do sufficient engine braking. I have personally towed up mountains in 5th or 6th that required 2nd or 3rd on the way down.

[Cranemec]

Same gear down as same gear up. Downshift before you start down the hill.