Coast Resorts Open Roads Forum: Wanted: feedback from drivers late model 300-340 Cummins

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Topic: Wanted: feedback from drivers late model 300-340 Cummins

Posted By: Ductape on 12/02/17 09:24am

The short version: if you have a recent Cummins 300-340 hp range does your coach hold 6th gear crossing interstate overpasses and mild grades? Or does it downshift at any mild rise?

Thanks for your feedback, and if you want to read all the whys and wherefores, the next post I'll drone on. [emoticon]

49 States, 6 Provinces, 2 Territories...

Posted By: Ductape on 12/02/17 09:25am

Backstory- we're in the market for a short coach, less than 36 feet. It's our preference (due to the types of parks we enjoy). Likely a Newmar Ventana or Ventana LE or Tiffen RED. We'll pull a large toad. Perhaps new, but we'll also consider going back a few years, but not before DEF engines.

I dislike a powertrain that's maxed out on torque and has to shift gears too often. Defeats the whole purpose of a diesel so to speak. And I've operated some trucks like that.

The real technical stuff: Most coaches in this range are built with the Allison 2000 series trans, a few have the 3000 Allison. The smaller transmission has limited torque handling capability and is used with the ISB 300 or 340, with peak torque ratings of 600 to 700. The Allison 3000 enables use of the ISB 360 which is 800 lb-ft torque. Which seems like not much difference, right?

But here's the thing; the 2000 series requires the use of torque managed engines, which limit the torque when shifting (not a bad thing) and also the torque in certain gears (and this is my concern). The 2000 series trans allows up to 700 lb-ft in gears 3-5. In other conditions it's limited to 575 lb-ft. Limitations on the Allison 3000 are not a concern with the ISB, as the trans can handle 1250 lb-ft and torque management is not required.

So... it would appear that the ISB360/Allison 3000 combo can draw on all 800 lb-ft of torque to maintain speed on a grade in any gear, whereas the ISB340/Allison 2500 by comparison can only use 575 lb-ft in 6th gear. That sounds like a recipe for easily dropping out of 6th with the smaller transmission. But does the real world experience match?

Thanks for your patience in reading my dissertation, and I appreciate your feedback.

Posted By: gutfelt on 12/02/17 09:29am

Ductape wrote:

neighbour has the 360 ISB in a 2017 tiffin pulls his ford F150 CC 4x4 and says severely lacks power in the hills(loaded pulling truck)
I guarantee you it will downshift when in the situations your asking about

Posted By: msturtz on 12/02/17 11:21am

I'm running a 2014 Thor Palazzo 33.3. It has a ISB 300 and Allison 2100 MH. I could go to ISB 340 / 700 with the same transmission. I have towed a 2015 Suburban, 2015 GMC Acadia Denali, 2016 Yukon Denali XL, and 2017 Ford Explorer. The I am at my max GCWR when I tow the Yukon and the motor home is empty. The transmission does downshift. I have traveled over the rocky mountains 4 times with this setup (pulling the Acadia) we had no problems. I probably will upgrade to ISB 340.

FMCA member

Posted By: Ductape on 12/02/17 03:23pm

Thanks for sharing, my pet peeve is not the mountains, as I don't have any objection to gearing down to climb a long grade, that's expected. What I dislike is a gear change just to climb an overpass in flat country, or a moderate rolling hill.

A little work with a spreadsheet has given me my answer I believe. Taking as an example recent Newmars:
Ventana with the 360/800 will produce 2,486 lb-ft at the axle in 6th gear @ 65 mph. Disregarding accessories and drivetrain losses.

Ventana LE with the 340/700 will be only 1,759 lb-ft under the same conditions due to torque limiting in 6th gear.

Dropping the LE into 5th gear provides full torque and gets the axle up to 2,476.

So in essence 5th on the Allison 2500 equipped coaches will be equivalent of 6th in a coach with the Allison 3000 and the 360/800 engine.

That's enough to convince me to seek out a coach with the bigger trans. Not to mention running the weight numbers I'd be over GCWR on the smaller Allison with cargo in the coach plus a 6k toad.

Posted By: nevadanick on 12/02/17 04:22pm

We had a 2014 40ft Red with 340hp. I dont recall it shifting on overpasses but the shifting is pretty seamless from 6-5. We were pulling a crewcab GMC with a couple motorcycles in the truck. I wasnt happy with the power so,went to a Phaeton with ISL.

Posted By: jplante4 on 12/02/17 04:26pm

Does your Allison had a mode button? My 3000 on the 300 hp CAT switches into an economy mode that delays the downshift until RPMs drop below 1500.

Jerry & Jeanne
1996 Safari Sahara 3530 - 'White Tiger'
CAT 3126/Allison 6 speed/Magnum Chassis
2014 Equinox AWD / Blue Ox

Posted By: gutfelt on 12/02/17 05:02pm

msturtz wrote:

A suburban weighs more than a 2015 yucon or explorer

Posted By: blownstang01 on 12/04/17 07:59am

Ductape wrote:

No help here, sorry. But you're first post with all the technical info and your name had me pegging you an engineer. This post and the spreadsheets come out, now I'm convinced. Carry on.

* This post was edited 12/04/17 08:09am by blownstang01 *

Posted By: Ductape on 12/04/17 08:15am

^^^ Guilty as charged [emoticon]

For part of my career anyway.

JPlante, thanks for bringing up the mode button; I hadn’t remembered that. My understanding is the Allison is programmable and the function of the mode button depends on what the builder has chosen. If there’s an economy function that holds top gear down to a lower RPM that would resolve my concern fully. I don’t mind losing a couple of mph in a short grade. What I hate is a downshift climbing an overpass and an up shift 200 yards down the road. Hard on the drivetrain and bad for fuel mileage.

And I do like to use the cruise control.

Posted By: wolfe10 on 12/04/17 09:07am

To my knowledge, ALL RV chassis makers have the Allison ECU programmed to default to power mode each time the engine is started.

So, to get into economy mode, one must push the mode button each time the engine is started.

To verify you are in economy mode:

Next time it is safe to accelerate from a stop to 45 or so MPH, do so at WOT (wide open throttle) with mode button off (engine started, but mode button not pushed) and then again after pushing the mode button (red mode light on).

Yes, in economy mode, transmission upshifts at lower RPM and downshifts at lower RPM.

Brett Wolfe
Ex: 2003 Alpine 38'FDDS
Ex: 1997 Safari 35'
Ex: 1993 Foretravel U240

Diesel RV Club:http://www.dieselrvclub.org/

Posted By: eheading on 12/04/17 03:01pm

We have had a number of motorhomes with Cummins and CAT engines with the 3000 series Allison transmissions. Our last Revolution LE had the 400 hp CAT. We now have the short Ventana LE with the 340 hp engine with the 2000 series transmission. Yes, it does shift down to 5th gear more than our 400 hp CAT did, but because it is governed at 2800 rpm, I have found that it does as well on hills as our larger engines did. In addition, the 2500 transmission is the smoothest shifting Allison we have ever had. The shift in and out of 4th gear was always a little rough, we can hardly feel this one shifting. In addition I like the 9,5 to 10 mpg compared to our 7.2 in our last motorhome, and I really like the flat floor all the way to the rear closet, a feature which I believe is only available with the 340 hp Cummins engine.

Posted By: msturtz on 12/04/17 03:13pm

gutfelt wrote:

msturtz wrote:

A suburban weighs more than a 2015 yucon or explorer

My 2016 Yukon XL is by far much heaver than the 2015 Suburban LTZ we had. That said I love the 6.2L V8. I only tow the Yukon for service work. If my wife had the Explorer I can still drop the motorhome off and tow the Yukon. But at that point I am empty so weight isn't a problem.

Posted By: Ductape on 12/04/17 04:49pm

eheading wrote:

Thanks for that, you're in one of the models on our short list. I am presently of the mind to hold out for Ventana (non LE) to get the Allison 3000. Tiffin REDs but only 2016 onward should have a 3000.

I have seen others who share your perception the 2100 or 2500 shift more smoothly, and that should be the case, considering the use of torque management to pull power during the shift.

I could love the fuel economy of the detuned 6.7, however the GCWR is 33,000 and with our toad we would scale more than that.

Posted By: Groover on 12/04/17 04:56pm

msturtz wrote:

Are you planning to upgrade the engine that you have? How do you plan to do that and how much do you expect it to cost?

Posted By: Ductape on 12/04/17 05:02pm

Another interesting thing I'm finding is that older coaches in some cases used the heavier transmission. E.G. in 2006 the Ventana had an empty weight of only 21,950, used the Cummins 300, but the GCWR is 38,000. The brochure for that year didn't specify the trans model, but it had to be a 3000 to achieve that weight rating.

The current shortest Ventana LE weighs 25,600. So it's starting two tons heavier and with a lighter duty trans than the 2006. Of course the LE was introduced as I understand it to compete at a lower price and cost of operation, nothing wrong with that.

Posted By: gutfelt on 12/04/17 05:34pm

Groover wrote:

msturtz wrote:

Are you planning to upgrade the engine that you have? How do you plan to do that and how much do you expect it to cost?

LOL Iam pretty sure he means upgrade to a mh that has more power because the
300 ISB towing a Denali xl 4x4 will be in 2nd gear at 25MPH going over mamouth mountain type passes LOL
frankly get he 360hp if your only going still with a ISB

Posted By: Groover on 12/04/17 06:08pm

Accidental re-post

* This post was edited 12/04/17 06:34pm by Groover *

Posted By: Groover on 12/04/17 07:06pm

gutfelt wrote:

Groover wrote:

msturtz wrote:

Are you planning to upgrade the engine that you have? How do you plan to do that and how much do you expect it to cost?

You may be right but the larger Palazzos do get the same engine with 340hp. I would be surprised if there is any real difference in the engines other than the programming (the same goes for the 6kw quiet diesel that also comes in a 7.5kw version with virtually the same specs). Getting it reprogrammed for more power would be technically possible but I doubt that Freightliner would do it. Also, I thought the that 340hp motor comes with the Allison 2500 series transmission but I could be wrong on that.

I am going to say that the performance of the Palazzo is better than you think. I also own a 33.3 and have had it in the Rocky mountains pulling a Taurus where it did reasonable well. As I recall it was able to hold 4th gear on all but a very few hills.

Posted By: Passin Thru on 12/04/17 08:04pm

Funny why they don't use a 1000 Allison. They have 765 lb-ft (11 - 16 MY)You can not buy a manual transmission in any Ford now, in a Chevy you can change one out as the clutch mount is still there. Don't know about Dodge. Since the 2017 model appeared, you can no longer tune them, no one can break the codes in the ECM. Next we will have speed limiters, inboard facing cameras and electronic logging.

Posted By: Ductape on 12/04/17 08:07pm

How to uprate your Cummins

I expect there are aftermarket vendors too. Banks etc.

Posted By: chuckftboy on 12/04/17 08:22pm

I have a 340 / 2500 combination and it never down shifts on overpasses or slight inclines It will down shift 6 to 5 in the hills but one would need to see it on the shift pad to know it happened.
As for increasing HP and torque, any Oasis shop can do it for about $450.00, its a simple program download. My son had his done last summer on his 2014 Excursion. Went from 300 hp 650 torque to 325 hp and 750 torque.

2019 Horizon 42Q Maxum Chassis w/tag
Cummins L-9 450 HP / Allison 3000
2006 Jeep TJ and 2011 Chevy Traverse Tows

Posted By: Ductape on 12/16/17 07:09am

I made an opportunity to test two coaches with the varying power trains, and I'll share the result in case this interests someone else shopping in the future. Coaches were identical models, but differing trim level; one with 340/2500 powertrain and the other with 360/3000. Same gear ratio in the axle and similar weights, the higher optioned coach with the 360 probably about a thousand pounds heavier due to options.

The 360 powered coach was noticeably more responsive at low speeds and accelerated more quickly from a dead stop. As expected due to torque limiting in lower gears with the Allison 2500. This was a difference you could feel in the seat of your pants.

The 2500 does indeed shift more smoothly than the 3000. Shifts from the bigger transmission were smooth, but perceptible. The 2500 shifts so smoothly (again with torque management) that they were imperceptible.

On a grade -using a short hill that's about 4% at it's worst slope as a benchmark- I ran the hill at 65 with each coach in economy mode, cruise control on. The 340/2500 lost 2 mph on the hill and regained speed after cresting the hill, no gear changes of course. The 360/3000 coach lost 1 mph and then accelerated back up to 65 on the climb, all in 6th gear. Speeds measured with a GPS.

Repeating the hill in normal mode and driving with my foot the less powerful coach dropped into 5th to hold speed.

In the intermediate gears 3-5 (where the Allison 2500 is not torque limited), the difference in these coaches is not really perceptible. Accelerating or holding speeds on a grade in those gears the coaches feel very similar and the performance difference between 340 hp and 360 will not be felt. In gears 1,2 and 6 the effect of having the full 800 lb-ft of torque is perceptible.

Posted By: tropical36 on 12/16/17 10:25am

Ductape wrote:

Rule of the thumb, without all the technicalities, is to have around 10HP per foot, which provides a decent amount of torque and is usually more than sufficient to handle a fairly heavy toad as well. It ends up being with the amount of weight you're trying to move, per the engine size.
You stated under 36ft, so story short, I'm most sure if you get a 340HP power plant in a 34ft coach, you're good to go as well or better than many. Anything close, should serve you well, also.
With our almost 41ft and grossing a little less than 37K lbs. including the toad, we spend most of our time in 6th gear, over all kinds of terrain.

"We are often so caught up in our destination that we forget to appreciate the journey."

07 Revolution LE 40E_Spartan MM_06 400HP C9 CAT_Allison 3000.

Dinghy_2010 Jeep Wrangler JKU ISLANDER.

1998 36ft. National Tropi-Cal Chevy Model 6350 (Sold)

Posted By: DSDP Don on 12/16/17 02:07pm

"Ductape"......We owned a 36' 2005 Monaco Diplomat for almost ten years and took it all over the country, including MANY national parks, where we camped inside the park. Those included Yellowstone, Yosemite, Zion, Rocky Mountain etc. We eventually sold that coach and bought a TRUE 40' coach, our Newmar Dutch Star. We've taken that coach to all the same places we took the Diplomat. The Dutch Star is 36" longer than the Diplomat that measured 37'.

In all honesty, sites typically larger than 35' are fewer and far between, but they do exist and we just have to plan ahead at places like Yellowstone.

With all that said, put away your engineering degree and angst, and buy a 40' Ventana with the 400 ISL. All your problems will be solved.

In 4 years of owning the Dutch Star, we haven't regretted adding the 36" in length.

* This post was edited 12/16/17 02:16pm by DSDP Don *

Don & Mary
2019 Newmar Dutch Star 4018 - All Electric
2019 Ford Raptor Crew Cab

Posted By: Ductape on 12/16/17 03:14pm

Thanks, Don. If I could talk both of us into a forty footer I'll skip the Ventana and go directly to the Dutch Star. [emoticon]

Posted By: DSDP Don on 12/16/17 06:04pm

"Ductape".....Here are some talking points, or should I say pictures. The first is my 37'Diplomat at the Watchmen Campground inside Zion. You can see there is room for another six feet.

[image]

We don't take photos of the coach in the campsite like we use to, so I really don't have that many pictures of the coach itself. In this photo, we're at Yosemite Upper Pines at Thanksgiving. The coach in the background is a 41' Monaco Camelot. My 40' is to the right of the turkey. There are several sites there that will take a 40' coach.

[image]

Lastly...I only have the view through the windshield as we enter the Yellowstone west gate. [emoticon]

We stayed at Fishing Bridge.

[image]

The new coaches have a 55+ wheel cut and can really crank around to get into tight spots. Just some confusion for your decision!

Posted By: msturtz on 12/17/17 02:05am

gutfelt wrote:

msturtz wrote:

A suburban weighs more than a 2015 yucon or explorer

I have a Yukon XL it weighs more than a Suburban.

Posted By: tropical36 on 12/17/17 09:01am

A little off topic, but it seems that the only people that claim not being able to find large enough sites in parks are the ones that have never owned a large one of 40ft or more. Occasionally yes, but not the norm.
I do remember once with being on the phone and calling around in the San Francisco area and not having much luck. It was summer and of course most of the CA coast line was pretty active with RV's. Anyway, we went on up to the Petaluma KOA, where you could have brought in a semi without much difficulty. They even had a field for overflow, in case they didn't have a site available upon your arrival. Their van conducted tours of the city, right from the office, so not a problem with being up the road a ways and we used our toad for getting to the ferry, as well. Just saying, that there's always someplace to park, no matter what your size.

Posted By: Ductape on 12/17/17 11:59am

But that's exactly the point. You ended up in KOA... Thanks but no thanks. [emoticon]

Posted By: tropical36 on 12/17/17 12:59pm

Ductape wrote:

But that's exactly the point. You ended up in KOA... Thanks but no thanks. [emoticon]

I said once and not the norm, with however you one might feel about a particular stay. The thing is, we're not about to go without what we like in a coach, just because it might be a little large for some RV parks and again, far and few in between.
You should see the size of some rigs, inside Glacier NP at their Apgar campground, for instance.

Posted By: DSDP Don on 12/17/17 01:56pm

Just to clarify what "tropical36" brought up, there really isn't anything around San Francisco, even for a small rig that is worth staying in. There is a parking lot near the stadium, but it is literally that, a parking lot.

The Petaluma KOA is actually one of the really good spots to see San Francisco either in a Class B or a 45' DP.

Posted By: Mile High on 12/17/17 02:38pm

We have the longest Winnie made in 2013 at 43'6" and in the year and half we have had it, I've struggled fitting a few times, even at KOAs. Sometimes its the tight turns that get me, not the length of the driveway. We stayed at a private campground in Truckee, CA and I thought I would never get that thing parked in there.

2013 Winnebago Itasca Meridian 42E
2013 Jeep Wrangler Unlimited Sahara Towed

Posted By: msturtz on 12/17/17 04:06pm

What is being missed here are a few things. When we had a towable we were about 60' long & 8'6" wide with a bumper pull overall length. I drove around downtown Salt Lake City UT & Portland OR including parallel parking. It wasn't fun but I was able to do it without trading paint with anyone. In certain situations other rude drivers were laying on their horn as if that would speed me up. I have also taken our DP off road onto a one lane gravel service road. Again slow speed is key don't be afraid of getting out and looking "GOAL". Many parks won't take longer rigs due to inexperienced drivers rather than actually being unable to accommodate them. Modern rigs have a 55 degree wheel cut. That makes them much easier to turn.

* This post was edited 12/17/17 04:20pm by msturtz *

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