Hill Climbing

wolfe10 wrote:
I agree with you, driving a gas rig, particularly one with a high RPM engine such as the very good Ford V10 is VERY, VERY different than a large displacement, turbo, inter-cooled diesel with Allison transmission.

Actually, my F450 was a 7.3L PSD.

I always bragged that I let the transmission decide on the shifting point when climbing and never had overheating problems. But this year when climbing north of Phoenix on 17 and the outside temperature was 90 degree's the engine heat indicator started climbing towards the upper limit, so rather than risking it going in to limp mode I had to manually shift so I could hold 2200 rpms and the heat stabilized. So I would say let your transmission do the shifting, but keep an eye on the engine temperature.;)

I always let it down shift as it needs too. I assume that's why it's called Automatic. Now if I come upon some slow traffic going up hill I slow down and shift it down.
We had a couple we use to travel with, every time he came to a hill no matter how steep the hill he would shift it down to now matter what his speed was. Every time he did it the blue smoke came out from under his MH, I asked him why and he would reply he was getting a run for the hill. I know of 2 transmissions he replaced. I guess to each his own.

I personally prefer to manage the gears myself in the hills. I find that by the time the tranny downshifts on its own, I'm behind the curve. If I see a steep hill coming I downshift before the climb starts and get on the throttle to pick up speed before the hill hits its steep grade. On the really ugly grades here out West I just downshift and grind them out. Sometimes it is a slow haul in 3rd or 4th.

Proper RV braking on a downgrade

I agree with this:
"The use of brakes on a long and/or steep downgrade is only a supplement to the braking effect of the engine.
Once the vehicle is in the proper low gear, the following is a proper braking technique:
(1) Apply the brakes just hard enough to feel a definite slowdown. (2) When your speed has been reduced to approximately five mph below your "safe" speed, release the brakes. This brake application should last for about three seconds. (3) When your speed has increased to your "safe" speed, repeat steps 1 and 2". From California DMV.

2oldman wrote:

wolfe10 wrote:

2oldman wrote:
Downshifting before the hill is easier on the tranny.

Would like more information on that one-- this is an Allison 3000 series.

When you're already on a hill and your tranny needs to shift, that's more stress than anticipating the hill and shifting sans load. Kinda like downshifting a bicycle derailleur before a hill, because once you're on it, it's pretty hard.

That said, perhaps the Allison etal are really good at shifting under load and it doesn't really matter. I remember my F450s tranny was not a smooth shift under load.

As posted, the Allison is a VERY robust transmission.

Second, there is less stress on it/less HP being generated at peak torque RPM at WOT (wide open throttle) than at higher RPM at the same throttle position. And while climbing, whether on cruise or manual throttle, it will very quickly go to WOT on a grade.

I agree with you, driving a gas rig, particularly one with a high RPM engine such as the very good Ford V10 is VERY, VERY different than a large displacement, turbo, inter-cooled diesel with Allison transmission.

Both Caterpillar and Cummins KNOW that the way to climb a grade using the least amount of fuel is at or just above peak torque RPM even at WOT. And they can sustain that for HOURS (as long as they do not overheat).

I found my 300 ISB and 5 speed Alison to work perfectly. I let everything work as it is suppose, never ever had an overheat. It normally stays at 198 F, and on a steep hill, it sometime hits 204 F for very short period.

The only time I use the shifter is to down shift on very steep hills or downhill tight airpin curves along with using the exhaust brake.

wolfe10 wrote:

2oldman wrote:
Downshifting before the hill is easier on the tranny.

Would like more information on that one-- this is an Allison 3000 series.

When you're already on a hill and your tranny needs to shift, that's more stress than anticipating the hill and shifting sans load. Kinda like downshifting a bicycle derailleur before a hill, because once you're on it, it's pretty hard.

That said, perhaps the Allison etal are really good at shifting under load and it doesn't really matter. I remember my F450s tranny was not a smooth shift under load.

The key word in your original post was "Allison"

That is one of the finest transmissions made (Check that.. It is not "One of the" even FORD says it is the best) and it is smarter than most drivers.. Myself included.

So yes.. letting it do it's thing is a good idea.

Read and undrstand the Grade Brake feature if you have it. Also fantastic.

bluwtr49 wrote:
On longish steepish grades I'll normally force a downshift to 5th or even 4th and keep the RPM up to 1800 to 2100 (Cat C-12) or so. This prevents any overheating and it's easy to maintain my speed. 4th at 2100 is about 60 or so.

It's all about what feels good. On not so steep I let the tranny do it's thing and keep the cruise engaged.

x2 I usually go to 4th