On my 1996 FT, the transmission displayed the current gear I was in. Virtually always when running along at 60mph or so, I was running in 6th gear. No surprise, just as expected.
With my "new to us" 2003 FT we got last summer the current gear is not displayed, so I have had to wait until I got my Poor Man's Silverleaf working to know what gear I was in. Much to my surprise, while running along at my normal 60mph or so, I find I am in 5th gear. In the recent drive from Palm Springs to Bend, I only saw 6th gear appear on a couple of occasions when going down hill.
So, it makes me wonder what gear other folks are running in. Any feedback would be helpful.
I read on another forum that the engine ecu has a max speed setting that affects when the transmission shifts to 6th. Anybody have any info on that fact or fiction?
Jim
Mine does the same as Dave. DAN
On my 1995 U320 M11, I am in 6th at 52 or 53 mph. Cruise all at 55 mph in 6th but I am usually faster.
Ditto. But will be interesting to see if it responds the same after my rebuild, don't see why it should change. Time will tell.
Roland
mine is the same as Rudy's. Around 52 mph.
Mark
Jim, like you, it took us about 3 months to discover that. :o
I checked with Pacific Power Products in Ridgefield to see if the shift point could be changed to 57 or 58. They advised against it. I never checked further. I set cruise to 61 and it shifts to 6th on flat road; this always worries me when driving in CA though.
Jim, are you sure of the mode the transmission is in. Maybe that would change the shift point for sixth gear. Mine defaults to econ mode but I know others default to power mode. Just a thought.
Mark
That sounds about right if you are doing 55. I have the 8.3 and 5.13 gears and mine will go in 6th at 55-59mph on flat. This is too low because at 65-70 I'm running the engine way too fast.
6th gear is a double over-drive on the allisons. I feel the final gearing should be made so that 6th gear is only used on the highway at crusing speeds (60-65mph +).
Our '03 U320 also needs to be around 61-63 mph to shift to 6th and stay there on the highway (at around 1350 rpm).
In 6th at 62 mph or 5th at 57 mph no real difference in fuel economy (in fact, may be slightly better at the lower speed and that's like attributable to wind resistance).
Ours is the same as Michelle's, have found that at peak speed in 5th gear, we get the best MPG. Shifts to 6th gear right around 61-62 MPH, RPMS drop down and you are putting more of a load on the eng.
How fast do ya'll normally set the cruise control at?
Into 6th @ about 61. Usually set cruise @ 63.
I am like Dave too. 62 into 6th and down to 59 or so. I did do an experiment this fall and drove out to Iowa at 55 as a max speed. I got better fuel mileage but it added a day for about 3/10ths. It added a day to my trip and that was ok too but last trip I moved back to 62-63mph.
I'm changing gearing so I can do 65-70 on flat at a lower RPM....I have to do some figuring but I'd thinking 1500-1600 around 65.
I often drive detween 55 and 60 and vmspc reports 6th gear. But mine is a u295.
Hi Jim,
Our 1997 U320, M-11, 4060R trans, does just as Dave M's. Never into sixth gear until 62 mph.
Raymond
My 400 ISL is in 6th around 54 or thereabouts.
Mine is around 53 to 55 in econo. 60 in power.. 1500 rpm at 69 to 70 . with cruise on at 1600 rpm is
73 to 74 with toad and full of fuel and water. I will get 7.85 mpg over 400 miles or so going through Alabama. I'm very happy with that.
You and I have a 3.91 rear axle ratio I think. The newer m11's are geared lower at 4.31?
Mine shifts in sixth at 55mph I think.
The shift points are adjustable by a shop.
Torque peak is 1350 rpm on the 450.
Needs to be in 6th at the 60 I would think.
Different tire size?
I have been interested in posts such these for some time but find it hard to get my arms around the data.
I have a 300hp mech. Cummins 8.3
Someone else has a, say, 450 Ixx
Some one has a 1,000 hp electric... :P
I would think some kind of tabulation by engine might be useful.
Along the same vein, I would like to find a torque curve (or something I can maybe understand) to give me a clue about rpm ranges I can live with and when I should start screaming (before the engine preferably).
I cruise at 62 at 1850 rpm. The transmission has been in 6th since 1500 probably.
When I gear down to descend a hill do I worry at 2200, 2400, 2600,..?
Just another morning full of finding things on the Forum to worry about.. ::)
Then ours or yours was reprogrammed I think. 55 mines in sixth.
The height of that Phenix will kill your fuel economy. As long as you are having it custom built, maybe 320 like height and a GV nose would be in order.
Howdy Elliot
Boy, ain't it the truth!!! I think I'll go for the 15yr single malt..
Dave A
Seriously considered dropping down to 5th gear and 55mph + - heading into fierce headwinds in Texas two weeks ago.
Here is the information from Cummins Quickserve on my 300 hp 8.3, you can get the same info on your engine by registering on the Cummins website. As I read it, peak torque and maximum efficiency is at 1300 RPM, a max governed hp of 275 @ 2400, High Idle is 2710 rpm above which you are in peril. Little foggy on just what "high idle" is, maybe someone more knowledgeable can explain it.
Electronic Parts Catalog - Option Detail
Option Group Graphic Film Card Date
Cart Ref No Part Number Part Description Required Remarks
FP97356
Fuel Pump
Fuel Pump...(More)
Engine Family: C Series
Engine Cylinders: 6
Advertised HP: 300 @ 2200
Governed HP: 275 @ 2400
Torque Peak (lb-ft): 820 @
1300
Fuel Pump Type: Inline
Pump Manufacturer/Model:
Bosch P7100
High Idle: 2710
Governor Type: RQVK
High Pressure Tube ID (mm):
1.8
Boost Control Provided: Yes
Shutdown Device: Electrical
Compatible Fuel Rating - FR:
9748
CPL: 2102
Certified by: EPA
CARB Taiwan EPA
Certification Year: 1997
Certification Status:
Approved
Governor Break RPM: 2475
Governor Regulation (%): 9.5
High idle= with no load on engine. Would apply to going down a hill with exhaust brake/engine brake on. No fueling, the engine is doing no "work".
All three numbers are VERY important on any engine to allow you to maximize economy, performance and engine braking:
Peak torque RPM
Governed speed (maximum engine working speed)
High idle/max permissible RPM (maximum engine speed in overrun/non-working)
Very interesting. I have only made one long trip so far (2750 miles). I noticed my shift to 6th occurred at approx 65mph. I could then coast down to 62 and set the cruise. At 62 mph engine rpm is a shade over 1300. The shifting rpm seems to be at 1500. That said, if aggressively accelerating shifting rpm is at 1800.
I have wondered if travelling at say 55mph in 5th, would permit the same or better fuel economy? I guess another question would be; is one better to run in 6th gear at the lowest possible rpm, or run in 5th at a higher rpm? Tom
In our experience (noted above), for our coach there is no improvement in fuel economy bumping into 6th gear. Wind resistance factors increase as speed increases, and it appears this negates the higher gear. In fact, in a headwind we will intentionally stay at a lower speed/lower gear.
In my experience, on all brands of diesels, high-idle has always just been another word for no-load RPM. This means, push the pedal to the floor in neutral and the governor should hold the RPM at 2710 +/- a few.
Also, don't confuse peak torque for max HP. Torque is just a force...HP is power (which is rate of work done, to get back to basics).
To put this in context, on boats or electrical generators, you will rarely see any specifications talking about torque on the prime mover. All that is discussed is power. Torque only comes up to ensure correct driveline equipment sizing (gears, couplings, shafts, etc).
But one must compare the HP curve and the Torque curve and analyze the entire system. How much HP is being made at that torque peak?
What RPM do you want to be at to climb that mountain as fast as possible...max torque rpm or max HP.....think about it.
'morning dave
Pour one for me to !!!
Torque gets you up the hill, horsepower gets you up fast.
Roland
I have driven many of the older motorhomes in the industry with more power to weight ratios than my u320.
If memory serves me they all got better mpg.
Obviously the smog standards affected this.
Favorite was the original unicoach with the hotted up series 60 Detroit. Screamer.
The old signature with a m14 at 444/1850 had a strong enough jake to feel like the retarder.
8v92 concept. Fun. What hills.
My m11 is not in the ballpark. Will change out the muffler soon and see.
I think I may have found someone who will not admit publically that they can reprogram the ecu in the engine if I left it off for a few days.
I have had that happen a few times long ago where the shop mentioned I would like the coach better but gave no details.
The m11 works ok just flat on top. I hope that's the muffler?
I guess I drive too fast. My last trip across West Texas on I10, I was in 6th for 350 miles. In Houston I drive across town in 6th gear. It's just easier to stay with the flow of trucks.
All it costs it fuel.
My experience is very similar to TheBrays. I had my heart set on a M11 when we were looking for a coach, but it wasn't meant to be. The perfect coach came along with a mechanical C8.3. I don't know why I worried, because it pulls just fine. It shifts into 6th at around 50 mph (1500 rpm). Our coach has a dual display, so there is no wondering what gear I'm in. We drove through the Flint hills (KS) coming home...cruising at 56 -57 mph, and it never downshifted. My wife, who was driving our Jeep Liberty toad - with a 3.7L - shifted out of overdrive long before reaching the top of the hills.
After 5000-7500 feet depending on the individual engine all diesels start to lose power.
The mid west and east coast users can use the 8.3 better.
Impatient Rocky Mountain drivers like the bigger motors versus 40mph on all 6 percent grades.
At that point you are in and out of the truck lanes on every hill. Not fun after a while.
I sold many, many ored 300 cats long ago because they would pull all the interstate grades without a car up to 90mph. And get 8mpg wide open. 10mpg at 70-75.
20,000 pound coach is how. Fun to pull everyone up long grades. Evil grin on your face.
Waaaay fun. Miss that.
I'm late to this discussion, but we went out for a drive today and I took notice of my 5th to 6th shift point. We have the same engine as Elliott (TheBrays) - C8.3 300hp. Our coach shifts into 6th at 53 mph (mode switch on or off - doesn't matter). Full throttle up-shifts occur at 1800 rpm. Normal shifts are so smooth that I can hardly feel them. Fortunately we have the digital readout to indicate both selected and attained gear. That Allison 6-speed is a SWEET transmission!.
I am wary of "lugging my 8.3 below 1400 as the Banks pyrometer starts to shoot up towards 1100 real quick . Truckers and older diesel RV owners alike have assured me that down shiffting and letting her spin over 2000 is much less harmful than seeing how much grunt she can muster down low...RPM's equal airflow , airflow cools exhaust side. Exhaust side is Achilles tendon of these brutes!
You should be OK at 1100 degrees with an normal range up to 1200. Factory recommended max is 1350 for that engine as I remember.
EGT probe should be pre-turbo otherwise post turbo reading will be at least 300 degrees lower than they actually are depending on the load. Post turbo readings are not really EGT and will give a false sense of security.
Pierce
I haven't yet been able to pay attention to the exact shift point, but our 1995 U320 (400 hp Cummins M11) is definitely in 6th gear at 55 MPH under typical conditions.
Probe is in manifold directly under turbo. Replacing manifold this week after work. Have to tap new manifold for probe.Have several busted bolts in head. Think its time to invest in a high quality tap set and reverse drills!
Since we don't have a pyrometer to detect EGT (450HP M11 ISM) U320 4200, is there any guidelines as to keeping EGT's low? I noticed that if I set cruise to 61mph it will tend to downshift to 5th pretty often. If I set to 62.5 or so it will tend to stay in 6th. But am I doing damage running up hills where it can barely hold 6th?
What guidelines would you follow to drop 5th or go over 2000 RPM to avoid high EGT's and problems they cause?
If you are not operating your STOCK engine (we are talking about modern, 4 stroke, turbo, after-cooled engines) below PEAK TORQUE RPM at HIGH THROTTLE POSITION you have nothing to worry about in terms of EGT.
I think in my case the transmission may not allow that then so I would have nothing to worry about.
Mine and others shift into sixth at 53-54 mph. Either your trans was programmed differently for your heavier 42' or its incorrect. Torque peak is 1350 rpm. Past that the torque goes down and the hp goes up.
Faster using the torque versus the hp.
Or the engine has a low power issue and the trans is trying to compensate for it by staying in the lower gears until enough hp shows up and it then upshifts.
Unless all 99 42's do the same thing from the extra weight?
Defintely needs the dr to look at this I would think.
Check for dirty air filter. The restriction gauges are notoriously in accurate.
This is one area where I think our coaches differ. Peak torque on the ISM is 1200 RPM rather than 1300 RPM. Several people here have noted that their shift point for 6th is at 62mph and at that speed it doesn't seem like especially high or incorrect RPM. It feels right. It's going maybe 1450RPM when it upshifts. The bigger engine also has the 4060R transmission and the rear is probably different and geared differently as well.
EDIT: I see you have a 320 as well. interesting. All I know is the coach feels fine and it hauls. It wil happily climb a big hill (say 3-4% grade) in 6th, 62mph 1400 or so RPM pulling a 6000 pound toad. Air cleaner is new, as is oil, coolant, hoses, and other bits.
Actually now that I think about it, for the longest time I thought I was in 6th at 55mph. It will not go into 6th until 62mph. Have you ever tried to go faster? You might be in 5th.
No in sixth for sure as I have the dual pad indicator on my 97 320.
You have the same tires and rear end ratio I think. You are shifting past the torque peak it seems which is either to put less stress on the trans by Allison on purpose or its been reprogrammed somewhere along the line.
Need a few other owners to post regarding their shift points to know if (1) it is on purpose (2) any benefit to lowering the upshift points (3) any different acceleration up grades if the shift points are lowered (4) does the raised shift points relate to smog standards on the engine which I doubt.
Long ago Allison mis programmed the shift points several different ways on ored 300's.
I fixed them locally and the project manage called me from Indianapolis asking why?
He was mortified that after all the meetings they got it wrong and some end user sales manager figured it out and had to fix it locally. Normal.
Corporate America at its best sometimes.
Like I said. If the others here are the same either its for a reason or they are all incorrectly programmed.
Maybe the torque at 1200 upshift caused a "jerk" or a noise. I can hear mine squeek a bit as it shift to fourth at the torque peak normally. I had the driveshaft and joints lubed to see if it affected this. A bit maybe. Heavier coach, higher power may have well needed the past the torque peak upshift. Not normal to upshift past the torque peak on any diesel I would think.
That's why I drove every new and used coach as the owners without a comparison had no idea what was right or wrong. I did.
I first noticed this shift thing when I was approaching a grade that I thought might cause a down shift to 5th. So just as I'm starting to hit the grade I shifted down to 5th. Wrong, it didn't shift, already there.
:-[
Well that's very interesting. There are definitely more than one of us in this thread alone. I wonder what the deal is. My coach is heavier for sure, but not that much heavier.
On our 03 it shifts into 6 th around 61 mph. When I am running 65 mph my rpm is 1405
Dave, you a wierdo? Â Say it isn't so.....
:-)
Found a fuel consumption chart for the ISM M11 I think.
The different fuel system the ISM seems to get better mpg at the 1450 rpm offset maybe by the wind resistance?
I just back from 1500 mile trip. Paid attention to it better shift in 6 at 63
But it would down shift a lot. At 70 1500 rpm 1550 is 72-73 climbs every hill and bounce 72 to 73. Got 8.4 mpg.
Are you running in econ?
Our coach shifts into 6th gear (econ mode, flat ground) at just over 55 MPH.
Our ISM turns at just a bit over 1500 RPM at 70 MPH and gets just a bit under 8 MPG while doing so in varied terrain. We're quite happy!
the ISM has a extremely high psi fuel injection system. multiple squirts per injection cycle. quieter. more efficient. better mpg. passes later EPA standards.
I am not done trouble shooting my celect plus's fuel system but I think I have maybe figured out what might have caused a power loss that was present when we got this in my opinion.
runs ok just does not feel right to me.
900 page shop manual and the test section is massive.
but most things do not fail. its the partial failure that does not light up the check light that's harder to trace down.
good shop foreman in my local cummins store. finally got to talk to him direct.
do you have an m11 celect plus or a ISM?
Our 99 320 shifted into 6th at 62 mph (ISM, 450hp, 1450# torque, governed speed 1800rpm.
Our 95 300 shifts into 6th at 52mph (M11, 400hp, 1350# torque, governed speed 2000rpm.
Both have the 4060 trans but different rear end ratios. They are very close in performance and weight (300 is 1K lighter).
jor
Have not seen any info on other than 3.91 ratios?
Oops. You are correct, Bob. Both of those coaches do have 3.91.
jor
do you have an ISM or a m11 celect plus?
The 95 has the M11 CELECT. The 99 has the ISM. I think it has the CELECT +. Not sure what the difference is between the two - maybe more programmable features?
jor
An ISM is different than a celect plus. the ISM had a ten times higher pressure fuel rail and electronic injectors allowing multiple injection events per firing stroke.
more atomization. quieter. more power.
I am asking as I need correct info to double check mine versus other similar coaches.
if someones m11 celect plus varies a lot from the others his or ours is different.
the internet shows several common failures on m11 celect plus's. one is the oil pressure sender unit. if it fails the ECM stops the motor. if you pull the wires from it after verifying the engine actually has oil pressure the check light will stay on but the motor will start and run.
I am going to have the dealer run a simple test on the other sender as if its incorrect on its signal sending the ECM reduces the fuel flow.
ISM does not work this way. they also have a waste gate turbo the m11 does not have. the m11 reduces the fuel flow to control the turbo boost.
ISM governs the fuel pulse itself electronically as far as I understand it.
so a report on mpg on an identical motor geared the same is good info for me. means I may not have found all the aged parts in the fuel delivery system.
mine runs ok but seems to flatten out as it revs. feels weird to me after driving countless diesels. that got me to search the internet on common m11 celect plus engines.
especially if you search power loss issues.
the sensors partial failure will not light the check light but a too quick of sending a full boost pressure will cause the fuel system to back off the fuel delivery way too early at too low an rpm.
the silver leafs HP indicator is a derived by rpm only number. no actual measuring device is in the system.
if you download the m11 shop manual from scrib'd and go into the trouble shooting area for each sender on the motor you will see the sender and the hookup for a mechanical gauge to verify the actual engines boost.
having the silver leafs indication of the sending units output electronically and the mechanical gauge hooked up next to it allows the only verification that the sender is sending the correct signal to the ECM. known to wear. known to fail.
I hope mine is bad as its an easy cheap fix versus the rest of the possible tests and parts.
its the intake manifiold pressure sending unit. be fun to find one that was wrong the other way where it was slow to report max boost a bit. hmmmmmm.
steinbauer does make a box to add 20% more power by increasing the pulse width of the ISM ECM's signal to the injectors but make nothing for the M11 Celect plus.
too low of a pressure system for much change of the pulse width.
my dyno run showed -50hp at full rpms at the cummins dealer in los angeles. silver leaf showed full 450hp.
the engine btw in the shop manual is actually rated at 420 brake horse power for our cummins parts list.
so the only way to verify things is to do the simple well known issue tests then look deeper.
its not bad just down on power per the dyno. fixed the fuel filter first. now the next step.
I want all that is supposed to be there then will see what is possible. fooling the sender a tiny bit might be a safe, easy mod.
if too much pressure indicated too early reduces power my next thought was the reverse.
would only be a ggod idea if every single part in the engine and trans and cooling system were in verified perfect condition and a boost temp gauge installed. and to use it.
maybe not needed as mine is close even down on power a bit.
from the other comments on power here I assume a fixed engine and a resonator will be great.
your m11 at 8.4 is an anomaly. maybe.
what tires are you running at what tire pressure?
thanks for any info. the shops service writer normally only wants the check engine light to go off per the shop foreman versus a possibly more subtle power loss.
if every one you drive seems the same is that the way they are or does everyone have the same worn part?
especially as the ISM'S all report better power and mpg. maybe its the system. maybe we all have worn inexpensive intake manifold pressure sending units.
similar mileage and use. makes you think.
the $500 worth of dyno times was necessary to verify the total output.
258hp with a bypassed winn system versus 420 minus roughly 20% for power train losses. should be 310 range according to two independent cummins shops at the rear axle on a dyno.
just me. driven too many faster big coaches. something seems incorrect. with the help here I can either find that's its fine or needs fixing.
bob