MSPUSMC
Massachusetts
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Joined: 06/10/2005
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We purchased an Allegro Bay 35 TSB FRED in 2007 with the Cum ISB 6.7 - 340 HP engine with an Allison 2100 MH 5 speed transmission. I was informed by Allison, after I gave them our Trans. No., that I can purchase a new shift pad and reprogram the transmission from a 5 speed to a 6 speed transmission. This is the same transmission in the 08's with a new shift pad and programmed to 6 speed.
The local Allison dealer will charge around $1,000 for the work. I spoke to Freightliner and Allison and they said that this would not void my warranty. The tech at Freightliner told me that the only reason they went to the 6 speed transmission was because of customer demand. The tech stated that my driving habits would determine whether on not it was worth it and suggested that I seek advice from RVers through the forum.
We live in New England and do weekend trips locally. Most of our trips are pretty hilly. We love it out west and will be spending a lot of time along the Continental Divide. We tow a 1996 Saab on a tow dolly. At 55 mph we get just over 10 mpg (9600 miles on RV) towing the Saab. The engine runs just over 1700 rpms at 55 mph. At 60 mph we get 9.5 towing the Saab. The engine runs just under 1900 rpms at 60 mph. I'm very comfortable driving at 60 mph in the right hand lane.
Has anyone had their transmission upgraded from 5 to 6 speed? Did it increase the mileage? If so, at what speeds? Would this upgrand significantly lower my rpms at 55 or 60 mph?
Can anyone who has an 08 or an 09 Allegro Bay FRED or any other FRED chassis give me an idea of the mileage they're getting with the Cummins 6.7 ISB with the 6 speed transmission?
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itsalleasy
USA
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Joined: 07/20/2007
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If you love the mountains and drive a lot in the mountains it would probably be better to save the $1000 for fuel, it is hard to go up and down mountains in 6th gear.
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st687
tampa Fl
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Joined: 10/09/2003
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5th gear=0.71:1
6th gear=0.61:1
Per Allison,only you can say if it is worth the money.
Doris &Bill
97 U270 Foretravel
05 Saturn Vue 265HP
When all else fails call a MARINE
Semper Fi.
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JFG
TN
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Joined: 07/01/2007
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Based upon the info given and at $5.00 gal for diesel, your payback would be about 40,000 miles.
Fred
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hershey
Albuquerque,(fulltime) NM, USA
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Joined: 06/04/2003
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I have a 5 speed and sure I'd like a 12 speed or at least the 6 speed, but I can't really say that adding more gears would help me. My fuel mileage is very good for a 36' MH.
hershey - albuquerque, nm
Someday Finally Got Here
My wife does all the driving - I just get to hold the steering wheel.
Expedition - Suzuki Grand Viagra
NASCAR 20 - - 99
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Dogbone
Ontario Canada
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Joined: 01/26/2004
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I would rather have a 6 speed than the 5 speed I have now but not sure if it would be worth the $1000 change over, I find now that I have to go around 55 MPH to get it to shift into 5th, once it shifts into 5th I can go about 50 MPH before it wants to shift down into 4th (unless of course I hit a hill). You probably would be able to cruise a little faster if it was a 6 speed and have the same RPM's as me in 5th but maybe someone could let us know when a 6 speed tranny shifts into 6th and how slow you go before it wants to shift into 5th.
2006 Holiday Rambler Vacationer 35SBD
36ft Workhorse 8.1
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KOG
Winterville GA
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Joined: 01/31/2001
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If you were cruising at 70mph it might be worth it. Since you cruise at nearer 55 and much of your driving is a even lower speeds it will never pay off in fuel cost.
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tatest
Oklahoma
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Joined: 05/14/2005
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Without a change in final drive ratio, you may not find the second overdrive useful. I suspect that you will find the engine will pull in 6th for very little of your driving. The ISB wants to run between 1800 and 3000 rpm, you are just getting into that range now in 5th.
For a larger diesel that operates over a narrower speed range (often 1200 to 1600 or 1800), the extra gear is more useful.
Tom Test
Itasca Spirit 29B
2001 Ranger Edge
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RCL
portola valley, ca
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Joined: 07/29/2004
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At 55-60 mph, my Allison 6 speed in a HR Imperial w/400hp Cummins doesn't even get into 6th gear. I have to bump the speed up to somewhere over 65 (don't recall the exact number) to get it into 6th. You have to decide if you will even use the 6th gear enough for it to be of value.
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wallynm
Los Alamos NM
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Joined: 09/27/2000
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We go into 6 th @ around 55-56 MPH and will shift down @ 53-54 MPH per our GPS and Trip Tec which is a ditigal read out. I think we have a 4.56 rear end ratio. This is when we are in economy mode. We are in a DP not FRED so I can not make a comparision specifically. If you got a ~20% increase im milage it would take ~ 100,000 miles to pay for itself if I did the math correctly. However the ride noise level might be less as you will travel at the same speed when in 6 th at a lower RPM. Every thing else being the same.
Have a Cat Engine Yahoo Group or Cat RV Club Web Page
Have a Freightliner Yahoo Group or FCOC Web Page
wallynm@yahoo.com
2002 DSDP 3567 PUSHED BY KITTY KAT
THOSE THAT DO NOT KNOW HISTORY ARE DOOMED TO REPEAT IT
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