Wanted: feedback from drivers late model 300-340 Cummins

[Ductape]

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. :B

[Passin_Thru]

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.

[Groover]

gutfelt wrote:

Groover wrote:

msturtz wrote:
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.

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

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.

[Groover]

Accidental re-post

[gutfelt]

Groover wrote:

msturtz wrote:
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.

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

[Ductape]

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.

[Groover]

msturtz wrote:
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.

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?

[Ductape]

eheading wrote:
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.

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.

[msturtz]

gutfelt wrote:

msturtz wrote:
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.

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.

[eheading]

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.

[wolfe10]

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.

[Ductape]

^^^ Guilty as charged 😉 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.

[blownstang01]

Ductape wrote:
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.

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.

[gutfelt]

msturtz wrote:
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.

A suburban weighs more than a 2015 yucon or explorer

[jplante4]

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.

[nevadanick]

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.