Community Forums

Mike&Chris · 06-08-2016, 05:30 AM

When pulling a long grade and the speed drops down to around 50 mph do you keep the petal to the floor until you reach the top and start to regain speed? This is my only diesel experience with the exception of a Ford 6.0 and we know what that was like.

brobox · 06-08-2016, 05:34 AM

I normally start down shifting if the RPM's start dropping and the Allison is not downshifting fast enough for me. Once you loose the RPM on a long grade, it is going to be slow going before reaching the top.

Tall Tex · 06-08-2016, 05:41 AM

Your Diesel engine is designed to be able to run at full throttle continuously. Just think about how off road equipment is operated. Don't baby it along. There are grades though that you want to manually down shift to hold your speed and back off the throttle a little. This would be to avoid up and down shifting which is not ideal for the transmission. Enjoy your new coach.

Grower15 · 06-08-2016, 06:12 AM

I was taught to keep engine at ~2000 rpm when climbing grades to keep from over heating and keep engine operating efficiently. Manually downshift as stated above to maintain 2000 rpm and keep the petal to the metal. Have never had a problem overheating.

vsheetz · 06-08-2016, 07:02 AM

Quote:

Originally Posted by Grower15

I was taught to keep engine at ~2000 rpm when climbing grades to keep from over heating and keep engine operating efficiently. Manually downshift as stated above to maintain 2000 rpm and keep the petal to the metal. Have never had a problem overheating.

Agree. 2000 rpm or a bit more. You don't want to be lugging the engine. WOT is ok.

Gary.Jones · 06-08-2016, 07:39 AM

My dynasty was equipped with a 370 horse Cummins which was a little too small for that coach.... I did have to manually downshift the Allison or the Cummins would overheat, so I was concerned with what this would be like with a 450.

Well, I got to really see it in action. Usually if I know I am approaching a long upgrade, I move from my typical 62 mph up to the speed limit or maybe 70. My experience is the more revs you have at the bottom, the more revs you still have at the top. Recently, I got on the interstate out of Camp Verde, AZ heading to Tucson. Unbeknownst to me, a quarter of a mile after I got on, I started up a 3 or 4 mile 6% grade. I didn't have more than 50 mph of revs in 6th at the bottom and I never got it back. However, I kept the "pedal to the metal" the whole way up and watched the engine temp like a hawk..... And the engine temp stayed right at the same point as when it was before the hill. It did not rise. The Allison perfectly handled the load, downshifting as needed to keep the revs up. The Allison did not early shift.... It shifted when it got down to ~ 1500 revs to put the tach back to 2000. I was impressed with how well the transmission and the Cummins worked in synchrony in climbing the hill. It was the slowest climb I have encountered since I bought the Anthem. It was my fault. If I had the revs at the right point before I started I would have been very happy. The fault was mine.

Gary

loisjop · 06-08-2016, 08:46 AM

When I had an Anthem I figured the Allison was at least as smart as I was about shifting. Keep your foot in it and let the transmission do the work. You won't hurt the engine and it won't overheat unless something else is wrong. I went over Wolf Creek pass,at 11,000 ft in CO. Several times and temp didn't get hot. Like Gary said gain a little speed if you see a long grade on a good road, otherwise hold it down and let the Allison handle the shifting. JMHO. Noel

rbr · 06-08-2016, 09:29 AM

Similar to what's been said above, at the Spartan Owners Academy "Big Mike" said when driving in mountains:

1) Don't use cruise control
2) Manually shift to keep climbing rpm in 1900-2100 range on an ISL engine (gear ratios are spaced such that you can't be exact with that)
3) "Let 'er eat" (his term for pedal to the floor)

I had a climb in my Anthem a few days ago over Luther Pass into the south end of Lake Tahoe where at times I was in the low 30's speed wise, even with rushing the start of climbs as mentioned above. Don't worry about it - folks that live around these kind of climbs expect to see slow trucks and RV's. One other caution - unless the law requires it (sometimes there are signs about it) don't be tempted to take a pull-out while on a long climb as you'll never get your rpm/speed back.

A related item from Big Mike:

4) Use engine braking on downhills to avoid burning up your service brakes, but don't let the engine rpm stay over 2400 for more than 5-minutes. (i.e. use your service brakes intermittently to get the speed/rpm back down)

RubiconTrail · 06-08-2016, 09:42 AM

Lots of goog info here, agreed.

One more thing...most states (and common courtesy) require you to pull to the right and activate your hazards, especially on a multi lane road if you are moving slow. My mark is 45mph. When I am below that, right lane and hazards.

MRUSA14 · 06-08-2016, 09:43 AM

Quote:

Originally Posted by loisjop

When I had an Anthem I figured the Allison was at least as smart as I was about shifting. Keep your foot in it and let the transmission do the work. You won't hurt the engine and it won't overheat unless something else is wrong. I went over Wolf Creek pass,at 11,000 ft in CO. Several times and temp didn't get hot. Like Gary said gain a little speed if you see a long grade on a good road, otherwise hold it down and let the Allison handle the shifting. JMHO. Noel

I agree with Noel on this. My old coach with ISC required manual shifting to keep the RPMs near 2000 in a climb, but with this ISL, the transmission really does a good job for you. On the few occasions where I have second-guessed the tranny I wound up wishing I hadn't. Just keep the throttle wide open and let the transmission shift for you.

As for Cruise control I use it uphill and it works great (more restful for the right foot), but you have to tap the brake at the top of the hill to turn cruise off so it won't overspeed you on the downhill.

Gary.Jones · 06-08-2016, 10:15 AM

Ron

I would personally never let my revs stay up at 2400 rpm on a downhill grade for anywhere near 5 minutes. I was initially quite concerned about how to come down a hill in a motorhome ( used to drive a 15 speed semi and so things were quite different) and asked a lot of questions. I was told by virtually everyone to use what is called "SNUB braking". Snub braking is taught to novice semi drivers in most driving schools and there are good discussions and videos of snub braking on YOUTUBE and elsewhere. In brief, it is applying the coach service brakes in a strong manner periodically, but intermittently. When my revs are up to lets say 2000-2100 on a downhill grade, even with the jake in high, I snub the speed down maybe 10 mph with each application of the service brakes..... If I am on a 7% grade, and have the jake on high, and the revs are at 2000 or 2100, that is when I apply the service brakes to decrease the coach speed maybe 10 mph or alternately, drop the revs down to 1500 revs, let off the service brakes, and let the speed gradually increase again the 10 mph at which point I snub brake again down 10 mph (a decrease of 10 mph from where-ever I am). On many steep, long mountains, with this coach and Jake, I don't have to snub brake at all, but if the revs get above the 2100 revs, I snub brake to decrease speed, and repeat. I have found it works great. But revving to 2400-2500 hundred is just too much stress on the Cummins in my experience.

Gary

rbr · 06-08-2016, 10:34 AM

Quote:

Originally Posted by RubiconTrail

Lots of goog info here, agreed.

One more thing...most states (and common courtesy) require you to pull to the right and activate your hazards, especially on a multi lane road if you are moving slow. My mark is 45mph. When I am below that, right lane and hazards.

Absolutely. Just to clarify, my reference to "pull-outs" above was a situation on a two-lane road where there are short stopping spots of extra wide shoulder. If you stop on one of those on a long climb it's very hard to get going again, but I have seen roads marked with signs like "Required to use pull-outs when 5 or more vehicles behind you".

rbr · 06-08-2016, 10:44 AM

Quote:

Originally Posted by Gary.Jones

Ron
I would personally never let my revs stay up at 2400 rpm on a downhill grade for anywhere near 5 minutes.
Gary

My only knowledge on that subject is Big Mike's statement (Spartan tech trainer and former Cummins trainer), but so far I've kept it to far less than 5-minutes as well.

My comment "use your service brakes intermittently to get the speed/rpm back down" was referring to what you're calling "snub braking", and does work very well in conjunction with the engine brake.

Gary.Jones · 06-08-2016, 11:31 AM

Ron

We are on the same page, completely. Although it might be within the capabilities of the diesel to take the high revs, I just didn't want people to think that doing it was good or appropriate or, needed in "standard downhill procedure" so I thought I would clarify. There are a lot of newbies on here at all times (like I was a few years ago) and I just wanted them to know that you don't have to do that to descend a steep mountain safely. I'll bet if I was in your passenger seat, I would not be grabbing the arm rests!!

Gary