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Old 01-11-2018, 04:23 PM   #21
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Disregard this info on RPM, Use the 1400 - 1900 recommended. For some reason people think this is a GM Duramax discussion. You have a Dynamax with a Cummins 8.9 ISL motor.
Well Excuuuuuuuuuuse Me! the Thread is entitled "Allison Transmission........".

It seems rather natural to assume it is a Duramax engine in front of it to me, since I do not know of any factory machine with an Allison transmission with a Cummins in front of it.

For some reason there are people on here who think it is OK to flame others who are only trying to be helpful without considering the reason.
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Old 01-11-2018, 04:39 PM   #22
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I am not sure they were trying to “flame you”, but making sure the Dynamax owners know the rpm was too high.
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Old 01-11-2018, 04:52 PM   #23
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Well Excuuuuuuuuuuse Me! the Thread is entitled "Allison Transmission........".

It seems rather natural to assume it is a Duramax engine in front of it to me, since I do not know of any factory machine with an Allison transmission with a Cummins in front of it.

For some reason there are people on here who think it is OK to flame others who are only trying to be helpful without considering the reason.
Like Halla said, no intention to flame anyone but you just accidentally told a newbie who doesn't know any better to over-rev their very expensive engine. In your RV class type the GM pickup chassis is probably the only rig using an Allison transmission behind a Duramax/Isuzu diesel. But in the Class A and Super C motor homes almost every rig has an Allison automatic whether its behind a Cummins or a CAT or a Volvo, etc.

Sorry if my response offended you but I wanted to very quickly make sure they understood the info provided was not applicable to them so they didn't damage anything.
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Old 01-11-2018, 05:47 PM   #24
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Like Halla said, no intention to flame anyone but you just accidentally told a newbie who doesn't know any better to over-rev their very expensive engine. In your RV class type the GM pickup chassis is probably the only rig using an Allison transmission behind a Duramax/Isuzu diesel. But in the Class A and Super C motor homes almost every rig has an Allison automatic whether its behind a Cummins or a CAT or a Volvo, etc.

Sorry if my response offended you but I wanted to very quickly make sure they understood the info provided was not applicable to them so they didn't damage anything.
Well I guess I got my feathers all ruffled up over nothing. I stand corrected AND Educated. Thanks Fellas!

One last point though, the newest version of the Duramax, the L5P has NOTHING to do with Isuzu. The only thing it has in common with the previous versions is the fact it is 6.6 Liters. Other than that it is new from the ground up.

After the get the gremlins worked out of it (like all new stuff) it will be one hell of an engine!
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Old 01-11-2018, 08:48 PM   #25
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Sure, same effect as changing differential gears. But then you lose some rear ground clearance and I'm told the DX3 doesn't have a lot to begin with. Why not just lock it in 4th or 5th on the control panel so it doesn't upshift too high?
Yes sir understood, but you can cut at least an inch off the bottom of the rear hitch from what I see, maybe 1-1/2" or 2", the hitch is what drags?

I did this on a Sportchassis and dropped 1-1/2" which was a bit much (Lost 3" in diameter)....

The take into consideration that these engines do not put out their FULL rated power when driven manually, but they will with Cruise Control "on"...I'll find the write up and post it...

They don't allow the driver full power manually, for obvious reasons from what I can tell....

On cruise control it turned mine into a beast that would run up hills and shift up and down perfectly keeping the engine in the sweet spot ALL the time...it was amazing how much it changed the pulling power....even running against a high wind it would drop to 5th on a slight grade and as soon as it sensed a level grade it was back to 6th...on steep grades it would shift down quickly to 4th when it sensed the incline and load...like I stated before, you'll think you gained 50 ponies minimally...that much difference...and also taking of from dead stop was incredible...shear power easily noticeable...
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Old 01-11-2018, 11:50 PM   #26
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You are correct. Full power is only allowed with cruise control engaged. That doesn't mean you can't manually shift. The trans will not let you down shift to a gear that will over rev the engine. So you should be able to down shift manually on a hill to get rpm into 1400 to 1900 range then engage cruise control. Keep an eye on the rpm and temp gauges. If temp starts to climb back it down a bit.

Like another user posted. This is not a pickup It is a 20K+ semi. Just happens to have a coach on the chassis.

Read your Allison 3200 trans manual and study till you understand.

BTW. The DX3 is set for Performance mode as default. Econo mode is with the mode light on. Performance mode starts in 1st gear. Econo mode starts in 2nd gear.

Happy camping!
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Old 01-11-2018, 11:59 PM   #27
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This link is a operators manual for the 3200TRV Allison it should work.
Taken from another thread.


https://www.dropbox.com/s/zyx40jwzph...654EN.pdf?dl=0
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Old 01-12-2018, 12:07 AM   #28
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Yes sir, and if you drop the rear tire diameter by 2" (1" Radius reduction)...you will never have to manually shift...it will automatically do it for you in cruise control mode...with full power available...

Put over a 100,000 miles on an M2 106...adjusted valve lash...changed transmission filters and fluid...replaced belts...repaired and replaced disc brakes...changed rear end grease...adjusted front wheel bearings...welded up hole in radiator while still on the truck with alum welding rods and a propane torch...replaced headlights/tail lights/running lights...many other various jobs including repairing faulty air pressure sensor complete...air tank check valve replacement...

Not only did I read the manuals I utilized MANY youtube videos for repairs which are great if you are doing a job for the first time and also it gives you a review of repairs from different videos, many many folks had different ideas on how to set front wheel bearing tolerance and also adjusting valve lash without timing marks to go by...got'er done and she ran and drove like a "top" when I sold it last year...
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Old 01-12-2018, 12:18 AM   #29
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I agree that changing the rear tires to lower profile will in effect lower the overall gear ration the powertrain "sees". Engine rpm will run higher for a given speed. Fuel consumption may also be higher.

But. 300 bucks a tire times 4 is a chunk o change after new purchase of MH.

I wasn't picking on you LTZ. I also have done a lot of driving and mechanical work
Just attempting to help a new DX3 owner with the driving and operation of the stock DX3.

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Old 01-12-2018, 12:19 AM   #30
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Yes sir understood, but you can cut at least an inch off the bottom of the rear hitch from what I see, maybe 1-1/2" or 2", the hitch is what drags?
I'll have to keep the hitch trimming in mind, I have a pretty steep down and then up section entering into the RV shop where the tail might drag. Also thinking I may need a manual valve to raise the rear end higher just for times like that.

On my Palazzo it always seemed peppier in cruise control. I thought it was just because the coach was moving and I didn't have my foot pushing through the firewall, but now I know.

I may have asked this before, but does the 8.9 have the high idle function if you activate the cruise control when parked like the 6.7 Cummins does?
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Old 01-12-2018, 03:28 AM   #31
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I agree that changing the rear tires to lower profile will in effect lower the overall gear ration the powertrain "sees". Engine rpm will run higher for a given speed. Fuel consumption may also be higher.

But. 300 bucks a tire times 4 is a chunk o change after new purchase of MH.

I wasn't picking on you LTZ. I also have done a lot of driving and mechanical work
Just attempting to help a new DX3 owner with the driving and operation of the stock DX3.

Yes sir, figured you were just being honest...the fuel consumption will change very little, the engine staying in it's sweet spot all the time actually makes it a pleasure to drive and tracking mine accurately and very closely it average 8.3 mpg overall...loaded...

I found that what killed mileage the most of all was wind resistance, really had nothing to do with gearing, if there was no wind could get up to 10 mpg....

A cross wind also caused the fan clutch to kick in and out more due to affecting the cooling...which hurt fuel mileage considerably as well...

The engine ran and pulled so well it was daylight and dark...

The Hankook Tires I put on were awesome, they held up WAY better than the Michelin XRV and Yokohamas I ran before...the Limited Slip Rear Axle was hard on tires due to the short wheelbase...

Michelin XRV are like $750 a tire...which is what a lot of the Motorhomes run...but they ride WAY smoother than truck tires...
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Old 01-12-2018, 04:08 AM   #32
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[QUOTE=RV Randy;1705547]
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Yes sir understood, but you can cut at least an inch off the bottom of the rear hitch from what I see, maybe 1-1/2" or 2", the hitch is what drags?
QUOTE]

I'll have to keep the hitch trimming in mind, I have a pretty steep down and then up section entering into the RV shop where the tail might drag. Also thinking I may need a manual valve to raise the rear end higher just for times like that.

On my Palazzo it always seemed peppier in cruise control. I thought it was just because the coach was moving and I didn't have my foot pushing through the firewall, but now I know.

I may have asked this before, but does the 8.9 have the high idle function if you activate the cruise control when parked like the 6.7 Cummins does?
Yes sir, will definitely raise the box hitch up as far as I can go with it, even to the point of cutting in to the fiberglass if required (easy to dress with split rubber cover)...then use a grinder and cut the two sides of the hitch up as far as possible, Brian said they were going to move the hitch up as well two holes minimally so considerable amount can be removed while still maintaining protection for rear cap and providing better clearance...

I am sure the high idle will remain for the 8.9L as it is required by most manufacturers as idling below 1000 rpm is not recommended by them, I am sure this has to do with several things including DPF operation to include oil circulation to top of engine as well as cooling circulation as well as Turbo Charger Lubrication which can starve at low idle...

Also after a hard pull most manufacturers will designate a cool down period before shutting engine off, I.E.After pulling hard on Interstate for several hours and one pulls over at a Rest Area or for Fuel, you should actually use high idle to cool down Turbo Charger then shut engine off...Mercedes recommends 10 minutes on their engines...

Another issue is fuel burn efficiency while idling, at high idle fuel is burned more efficiently and fully than at low idle...I said burned not used...
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Old 01-12-2018, 04:10 AM   #33
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https://cumminsengines.com/uploads/docs/4971288.pdf
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Old 01-12-2018, 01:33 PM   #34
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Interesting reading, I get that there are times that a cool down period is recommended before shut off. I see in the document where it says the ISL may invoke a higher idle automatically under certain conditions.

But it does not answer my question: Can you manually invoke fast idle on the ISL by having the cruise control turned on and then pushing the "set speed" button while the vehicle is parked and in neutral? That's the way it works on the Cummins 6.7 ISB. It was useful when starting after a long down time and getting air pressure built up quickly and keeping the charge voltage high. Otherwise the automatic leveling would not work right away because you would get "Low Voltage" warnings, especially when the engine was cold and the air intake grid heater was cycling on and off. As soon as you would touch the foot brake or put the tranny in gear, the high idle would shut off.
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Old 01-12-2018, 07:47 PM   #35
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Interesting reading, I get that there are times that a cool down period is recommended before shut off. I see in the document where it says the ISL may invoke a higher idle automatically under certain conditions.

But it does not answer my question: Can you manually invoke fast idle on the ISL by having the cruise control turned on and then pushing the "set speed" button while the vehicle is parked and in neutral? That's the way it works on the Cummins 6.7 ISB. It was useful when starting after a long down time and getting air pressure built up quickly and keeping the charge voltage high. Otherwise the automatic leveling would not work right away because you would get "Low Voltage" warnings, especially when the engine was cold and the air intake grid heater was cycling on and off. As soon as you would touch the foot brake or put the tranny in gear, the high idle would shut off.
Randy, if it doesn't have it it can be programmed in at a Freightliner Shop...I hope mine does when I get it, if not I'll definitely get it programmed in...IF they don't have it will be due to EPA regs more than likely, they are trying to stop all the idling diesels across the US...

My M2 106 had it and I used it all the time...for all the reasons stated before...
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Old 01-15-2018, 09:25 PM   #36
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Hmmm, I wonder if my 2005 M2 106 chassis with the Cat C7 is the same. I have been shutting the cruise control off in the hilly sections of the interstates so as to maintain more control. If i find any info online I will post it here.
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Old 01-15-2018, 10:51 PM   #37
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Does your unit have a Tow/Haul button/switch? If so, do you use it?
Lol
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Old 01-16-2018, 08:56 AM   #38
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Lol
OK, I admit I asked some clueless questions. At least I didn't make clueless/definitive statements.
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Old 01-16-2018, 10:33 AM   #39
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OK, I admit I asked some clueless questions. At least I didn't make clueless/definitive statements.
Thanks for bumping the post...
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Old 01-21-2018, 10:51 PM   #40
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Hmmm, I wonder if my 2005 M2 106 chassis with the Cat C7 is the same. I have been shutting the cruise control off in the hilly sections of the interstates so as to maintain more control. If i find any info online I will post it here.

For anyone interested, according to this manual

https://www.motor-talk.de/forum/akti...hmentId=435123

the Cat C7 does not have a "derate" option if the cruise control is not active. I did learn about Cat's "soft cruise" though.
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