Community Forums

joseyj · 07-13-2012, 07:10 PM

just joined...currently have a 5th wheel but looking at 40 ft. diesel pusher with 300 hp cummins and have some questions for anyone that has a 40 footer with 300 hp cummins turbo 660 torque. Is this 5.9 liter engine to small for this big coach??????. thanks, Josey

Steve Ownby · 07-13-2012, 08:41 PM

It will do the job. Yes, it's a little small. The rule of thumb is, it should have a minimum of 1 hp per 100 pounds of weight. An average 40' coach will most likely be somewhat over 30,000. This means that although the ISB will push the coach down the road at legal speeds, it will be struggling up the hills especially if you tow.

joseyj · 07-14-2012, 08:30 AM

thank you very much Steve for your reply. I am really torn about this motor coach...beautiful unit and the price is right!!! only 5,000 miles and loaded.
But, I don't want to have any major problems down the road and find it just want do the job. As far as the engine itelf goes....this is a very good engine...am I correct? Josey

jetfromtn · 07-14-2012, 08:55 AM

I have a coach like you are describing, 40' Pathfinder an tow a HHR. The 300 hp is not a ball of fire but it will do the job for you. The fuel mileage will be good. I have had a high of 12.5 to 9.8. The last two years I have averaged 10.2 mpg. IMHO if you like the coach, go for it. The 300 ISB will do the job.

jetfromtn · 07-14-2012, 09:10 AM

One more word of advise. Take the coach out to a steep hilly route, if you can and try it out. When I was looking at mine, I took it out on US 127 from Crossville TN to Pikeville TN down into the Sequatchie valley. It is a very steep ascent to the top of the Cumberland plateau and it did very well.

Steve Ownby · 07-14-2012, 09:15 AM

Josey,

The 5.9 ISB has been around in one form or another for a long time. It has now been enlarged somewhat and is now, I believe, 6.7 liter. There are a couple of issues with the 5.9 version. There was an engine block manufacturered in Brazil which is called the "53" block. Under certain conditions it was prone to cracking. There is a "dowel pin" issue which I know is problemic but I don't know the details. I'm sure you can google both and get lots of info.

Because the ISB is a low output engine it's generally equipped with lighter duty transmissions, but not always. Allison 1000-2500 transmissions are sometimes paired with the ISB and are not as desirable as the 3000 which is the standard against which all others are measured. The 3000 is a 6 speed with 2 overdrives and the others may be 5 speeds.

I'm not familiar with the Pathfinder. Who builds it? What chassis is under it? It's most likely a Freightliner. What year?

Do as much research as possible. There are a lot of very desirable coaches out there for yery good prices. Make sure you know what you're buying.

**Petro** · 07-14-2012, 10:03 AM

joseyj;

We are glad you joined us.

I would suggest you visit our Class A Motorhome Discussions in the Motorhome Forum section or the Cummins Engine Forum in the Power Train Garage Forums section. You will likely receive more replies there. Good luck with your search.

Don

Yukon Jack · 07-14-2012, 01:08 PM

Joseyj,
I have owned two Monaco Dynasty diesel pushers, a 1995 with cummins 300 hp turbo and currently own a 2001 Dynasty with a cummins 350 hp turbo and would be glad to help if I can.
Cell phone 817-308-2728

Happy RV'g

Jack

joseyj · 07-15-2012, 08:08 AM

thanks for all the input about the 300 cummins engine on the 40 ft. pathfinder. It seems some are happy with the engine and some feel the engine is definitely too small for this size unit. Got some great info from Monty...gave me lots to think about.
I will check into the Block 53 engine to make sure it is not that one. Also will check to make sure the Allison transmission is the 3000 6 speed...I think it is.
Will keep everyone informed of how it all goes. For sure I will be purchasing a diesel pusher in the near future..will just take my time and won't buy anything until Monty checks it all out.
Josey

joseyj · 07-15-2012, 08:12 AM

Hi Steve,
Thanks for all the input about the isb engine, especially the block 53 and the Allison tranny!! I am going going to look into that.

deSanford · 07-15-2012, 06:41 PM

The NEW 2500 trans are all 6 speed with 2 overdrives. You will find it behind the ISB340 6.7L Cummins it is lighter in weight and achives GREAT fuel mileage with some after market help (14MPG). deSanford