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lmurraytwst · 02-24-2013, 04:47 PM

We have a class a 2003 38' tiffin phaeton equipped w/ a cat. 330hp. & Allison tranny. We are newbies. We have been struggling a little bit going uphill , just wondering if this was normal. Would really appreciate any feedback.

TXiceman · 02-24-2013, 05:00 PM

Sounds normal. Depends on the hill grade, the speed you are expecting to maintain going up hill. Just like a car, a high powered sports car will do better getting up the hill than will a economy car with a small engine. 330 Hp is not all that much power for a 38' Phaeton. You need to slow down, let the gears drop down and keep the engine in the power band.

My diesel truck is 400 HP. You need to run up a hill with a similar sized and powered motorhome.

Ken

dennis45 · 02-24-2013, 05:00 PM

Quote:

Originally Posted by lmurraytwst

We have a class a 2003 38' tiffin phaeton equipped w/ a cat. 330hp. & Allison tranny. We are newbies. We have been struggling a little bit going uphill , just wondering if this was normal. Would really appreciate any feedback.

Not sure what you mean by Struggling but if you are new to a class A, you will find it somewhat slower than your car going uphill. Don't forget you are hauling a lot of weight up the hill.
That said, You should use your trany keypad to select a gear manually to maintain peak RPM/Torque which will be in the 2000 RPM range. This will also keep the engine/transmission running cooler by passing maximum air through the radiator. Letting the Allison do it's thing will work most of the time except on those hot days when the Engine needs all the help it can get.
Also remember, don't go down the hill any faster than you can go up. Use your Exhaust Brake to help control speed and when required, brake hard on the pedal to bring your speed under control on those long steep grades. DO NOT PUMP the brake pedal as you would with your car.

Diesels don't accelerate, they gain momentum.

Safe Trails,

t55watson · 02-24-2013, 05:08 PM

If the semi's aren't crawlin' up your rear your doin' good. Big long grade may drop you down to 45 or 50 and 4th gear. Just keep right and all will be good.

Pusherman · 02-24-2013, 05:23 PM

Let the Allison do it's job. Switch out of 'economy mode' going up a steep grade.

As others have suggested, downshift the tranny manually if you see the engine temps climb. Keep the RPM's at 2000, which provides optimum cooling if engine temps climb.

Mine slows down going up hill also, but not to the point that I can't keep up with the truck traffic (cars - yes, they will be passing us).

GaryKD · 02-24-2013, 05:39 PM

Hi lmurraytwst,
There are a few things left out of your OP.
1. How much do the coach and toad weigh?
2. Keeping up with the trucks?
3. Define "struggling".
4. Does the engine temp remain okay?
5. Do you manually downshift to keep the RMS around 2K?
6. Can you provide an example of a hill where the "struggle" happened? Length and grade if you have the information.
You may have a normal situation or it could be abnormal. Let us know some more details.

1ciderdog · 02-24-2013, 08:36 PM

To add to Gary's questions do you tow a vehicle and if so what vehicle?

lmurraytwst · 02-25-2013, 09:01 AM

1. Getting it weighed in the next couple of days in preparation of our 1st trip.
2. Yes
3. Bad choice of words, slows down
4. Yes
5. No, still learning on when and where
6. Approximately a mile on a 7 % grade ( guesstimating here )

Thanks so much...

ahicks · 02-25-2013, 09:32 AM

1. For a better idea of "normal" watch the semi's. You'll pass some (heavily loaded), you'll be passed by some (empty).

2. Relax. Put your foot on the mat and let the tranny do the thinking. Save your concentration for the trip down....

stuhly · 02-25-2013, 10:12 AM

Just down shift and hold 2000 - 2100 RPM. It will keep the heat down, and the speed up.

jauguston · 02-25-2013, 10:33 AM

Don't use Econo mode on hills. 2000-2200 rpm is your maximum horsepower rpm. I never use Econo mode.

Jim

deandec · 02-26-2013, 10:32 AM

FWIW, our rig slows to a steady 35 mph on an uphill 7% grade.

31,000 lb rig, 5,000 lb toad, pushed by 300 hp and 860 ft lb of torque.

jauguston · 02-26-2013, 10:52 AM

Dean,

What RPM is your tach reading at that speed. 36,000 lbs and 300 HP is not going to be real speedy.

Jim

chuck49 · 02-26-2013, 12:41 PM

Our 2005 Safari Gazelle (C-9 400hp Cat, 6 spd Allison) weighs around 32,000 pulling a 4,000lb toad. Specs on that motor say max torque of 1250lbs at around 1400 RPM. I like to keep the RPM a little higher than that on a long pull. Always watch the water temp. If it starts getting too high back off a little. The hotter that motor gets the better it runs (up to a point!) Like stated above, we out pull most of the loaded trucks but can't keep up with the empty ones on the big hills. These motors are set up so it is hard to hurt them if you keep the temp where it should be. An empty big rig only weighs a little less than my rig but will pull hills a lot better even with the "same" motor, but they are set up different. They say you aren't "lugging" these motors at lower RPM as long as the motor will accelerate when given more throttle. It is still hard for me to let the RPM get too low. I drove the old (not computerized) diesel trucks back in the 70s. We always kept the RPM between 1800 and 2200. Now that is too high. Depending on the grade (or not) I like to keep mine between 1400 and 2000. Climbing a long steep grade maybe around 1500 to 1700 to keep the torque more in the peak range. But keep and eye on that temp gauge especially in hot weather.