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Old 04-13-2018, 07:58 AM   #1
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Allison 2500 versus Allison 3000

I am certain there are threads about this subject already here but my search for them has proven fruitless.. so apologizing up front for starting another one. My question is fairly basic but realize the answer may be complicated... I am looking at an '05 Holiday Rambler Neptune 36PDD .. 300 ISB Cummins on a Roadmaster chassis. My only real issue is that it has an Allison 2500 rather than a 3000. Is the 2500 a deal killer on a 37' coach? And is the combination of 300 HP DP and the Allison 2500 an issue all by itself?
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Old 04-13-2018, 08:06 AM   #2
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you wont find the 3000 behind an ISB5.9 motor - ISB6.7 maybe.

They are rated at higher loads..

RV - Motorhome

del Ratio Max Input Power - kW (HP) 1 Max Input Torque - Nm 1 Max GVW - kg Max GCW - kg Reference Spec Sheet
1000MH Close Ratio 224 (300) 780 10000 11800 1000
2100MH Close Ratio 224 (300) 780 11800 13600 2100
2500MH Wide Ratio 224 (300) 780 15000 15000 2500
3000MH Close Ratio 336 (450) 1695 3000

the 2500 is also rated for higher rpm. Which is more common in the 5.9 motor. They tend to run better in the 2200-2600 range than most other diesels.
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Old 04-13-2018, 08:15 AM   #3
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I have no experience with either of those transmission models....
That said....I haven't heard much if any bad reports on either one.
And there are a lot of both models out there
If the price is right....... run it till the wheels fall off..then trade it for a puppy
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Old 04-13-2018, 09:30 AM   #4
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Hi ! Welcome to IRV2! We're sure glad you joined the gang!

Don't know anything about transmissions but interesting reading!

Good luck, happy trails, and God bless!
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Old 04-13-2018, 09:36 AM   #5
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The 3000 is preferable, but the 2500 is OK, just has a lower hp, torque and max load rating. If the rig is under on all of them there shouldn't be a problem.
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Old 04-13-2018, 09:51 AM   #6
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Quote:
Originally Posted by jimmy braden View Post
you wont find the 3000 behind an ISB5.9 motor - ISB6.7 maybe.

They are rated at higher loads..

RV - Motorhome

del Ratio Max Input Power - kW (HP) 1 Max Input Torque - Nm 1 Max GVW - kg Max GCW - kg Reference Spec Sheet
1000MH Close Ratio 224 (300) 780 10000 11800 1000
2100MH Close Ratio 224 (300) 780 11800 13600 2100
2500MH Wide Ratio 224 (300) 780 15000 15000 2500
3000MH Close Ratio 336 (450) 1695 3000

the 2500 is also rated for higher rpm. Which is more common in the 5.9 motor. They tend to run better in the 2200-2600 range than most other diesels.
Jimmy Braden...I see you are involved with a Holiday Rambler group which is a plus. In your opinion is this 37' coach underpowered with this engine and transmission?
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Old 04-13-2018, 11:03 AM   #7
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My understanding would be relate to tow rating, 2500 = 5,000 lbs and the 3000 = 10,000 lbs if you Dp can support the hitch and have the gvw available.
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Old 04-13-2018, 11:06 AM   #8
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Quote:
Originally Posted by jimmy braden View Post
you wont find the 3000 behind an ISB5.9 motor - ISB6.7 maybe.
FYI I had a 2003 34' Fleetwood Bounder Diesel with a 5.9 and a 3000 series trans. So they do exist.
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Old 04-13-2018, 11:07 AM   #9
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I have the same set up in my 36' MH. I average 8.5 towing my car, and live in NW, so I have driven it over many large mountains. I set CC at 63-65 and really have no complaints. I do not crest mountains at record speeds, but I am by far not the slowest either. I travel with friends whom have more HP/TQ that I travel with, have never held up travel days. I would own same set up again in a heartbeat...
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Old 04-13-2018, 12:31 PM   #10
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Typically, the issue with the 2500 versus the 3000, is that there is no room for upgrades. As an example. Our friends own a 2007 Holiday Rambler Neptune. It came with an Allison 2500 and 5.9 ISB. They were disappointed with the power and looked to add a computer chip. The problem......the 2500 was already at it's max rating and adding a chip would exceed the horsepower/torque rating. Consequently, they were stuck and unable to uprate the engine.

With that said, I think Allison transmissions should be in every vehicle. Just be careful that you don't buy something that has it's power limited by the transmission.
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Old 04-13-2018, 01:17 PM   #11
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My take. I am also looking, possibly considering a Neptune. 340hp/600tq. 2500 trans. Before I had a Safari, 300 Cat with a 3000 trans. Safari weighed about 23k loaded with a Honda CRV behind weighing 3400lbs.

The Neptune is turned up to 340 hp which is the MAX INPUT for the 2500 trans. The 3000/3200 trans is rated at 450hp input.

Thus the Safari was operating at a 66% load on the transmission. Plus it had 800lbs torque where the 340 5.9 Cummins has 600tq.

So, my take is the Neptune was built to be at a price point, a B Cummins with a 2500 trans, instead of a C Cummins with a 3000/3200 trans.

Personally I have ruled out this powertrain option in my searching for my next rig.
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Old 04-13-2018, 01:32 PM   #12
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Quote:
Neptune 36PDD .. 300 ISB Cummins on a Roadmaster chassis. My only real issue is that it has an Allison 2500 rather than a 3000. Is the 2500 a deal killer on a 37' coach?
The 37 ft length has nothing to do with it - it's combined vehicle weight, engine horsepower and engine torque that matter. See the next paragraph.

Quote:
And is the combination of 300 HP DP and the Allison 2500 an issue all by itself?
No. The 2005 version of the Allison 2500 is rated for up to 300 hp and 550 lb-ft or torque moving a maximum coach weight (GCWR) up to 33,000 lbs. That '05 Neptune fits within those parameters.

Somebody mentioned a 5000 lb tow capacity limit for the 2500, but that is not factual. The tranny doesn't care if the total weight in all in one vehicle or is combined in a coach & trailer. It has to move the total combined weight regardless of how it is distributed. Because of the 33,000 lb combined limit of the 2500, heavier bodies coaches typically get lower towing limits, but if the coach itself was light enough, say 23,000 lbs, then the 2500 would be rated to move it plus a 10,000 lb trailer (33k total).

I believe this Allison brochure is accurate for circa 2005 (later years of 2500 have higher ratings).
https://www.rvtechlibrary.com/transmissions/specs.pdf
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Old 04-13-2018, 01:32 PM   #13
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This was exactly the information I was looking for and appreciate the responses especially from those who have owned or had personal experience with the 2500. It answers the questions about GCW, GVW, and power. The GCWR for this specific coach is rated at 32,500 lbs. The coach itself is rated at 25,500 lbs. It is a shame as the coach we were looking at ticks off all the boxes but we plan to go full time and I do not want to be dealing with not enough power. Thanks.
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Old 04-13-2018, 01:38 PM   #14
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I wrote a blog article a while back about looking at the ratings on coaches carefully before buying. In the end, I upgraded because the math told me to.

Numbers Matter | waywards
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