5 speed vs 6 speed Trans

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RedandSilver

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I went and looked at a Class A 36 ft with a 300 Cummings and it only had a 5 speed Tranny.
It was a 2005.

My questions are:

Do they even make a 5 speed any more?
Is a 6 speed always preferred over a 5 speed?
Is there ANY advantage to having a 5 speed?
Would a 5 speed in a diesel RV be a deal breaker?

Anything else I should know about Transmissions?
 
The 6 speeds I have had contact with were double overdrive Allison transmissions, the 5s were probably only single overdrive.>>>Dan (The difference would be better hill climbing and a little faster thru the gears,
 
Way back in 2001, I bought my first 1993 DP, a large 34 footer, which was equiped with a Cummins 5.9L and a 6 speed Allison MD3060 tranny and it was a beauty to drive; the last 2 gears were Overdrive, so at 1800 RPM in 6th gear, my little "250 HP" engine was cruising at 65-70 MPH depending on the wind condition!  ;)
 
RedandSilver said:
I went and looked at a Class A 36 ft with a 300 Cummings and it only had a 5 speed Tranny.
It was a 2005.

My questions are:

Do they even make a 5 speed any more?
Is a 6 speed always preferred over a 5 speed?
Is there ANY advantage to having a 5 speed?
Would a 5 speed in a diesel RV be a deal breaker?

Anything else I should know about Transmissions?
Click to expand...
What make and model Class A 36 ft with a 300 Cummings are you looking at?
Bill
 
If I recall correctly,  some coaches with an Allison 5 speed can be reprogrammed for 6 speeds. I seem to remember call that the chassis/coach builder specifies what is optimum for that coach. But then again,  I could be wrong about the whole thing. I'm sure someone that knows for sure will jump in here with the correct information.
 
WILDEBILL308 said:
What make and model Class A 36 ft with a 300 Cummins are you looking at?
Bill
Click to expand...

It was a Holiday Rambler - Sorry don't remember the model.

Reason I posted the question was that I think a 6 speed is much preferred over a 5 speed.
Maybe a 5 speed costs less and was used in certain models to keep the cost down.  IDK.

One reason I'm looking at a diesel is for better fuel mileage.  I have to believe that a 6 speed will
do better than a 5 speed.  So I'm not sure if a 5 speed will be a deal breaker for me but unless the rest
of the RV was perfect (is there such a thing?) it might very well be. 

That's what I want to know - who has a 5 speed and climbs mountains with a trailer and thinks it's just fine?
Or who has owned both a 5 and 6 speed tranny and know the pros and cons of each and therefore can tell me if a 5 speed
should be a deal breaker or not.

Thanks in advance for any help anyone can send my way so I can make an informed decision if I run into this issue again.  :-[
 
from everything I hear.....you can just figure an average of about 8-9 MPG in any motorhome,      gas, diesel 3-4-5 or 6 speed.
 
Allison had a couple trannys that were 5-speeds, all of them lesser models than the 3000 and 4000 series used on the bigger rigs. The 1000, 2000, and 2400 series trannys were first built as 5 speeds and later upgraded to 6 speeds. The difference is a second overdrive gear, as utah already said. I think they had all moved up to 6 speeds by late 2004.

By "lesser model", I mean they have lower horsepower and torque capability, and perhaps a somewhat less rugged design. That's not really important as long as the tranny matches the engine power output, since any of them is probably going to last  200k miles or more with reasonable care.

The addition of a 6th "second overdrive' improves mpg during long interstate cruises,where the slight difference in gearing has an advantage. You probably won't notice any difference in mpg unless you can spend hours at a constant 60-64 mph. Anything short of that and the tranny will be routinely shifting between 4th, 5th, and 6th and the extra gear benefit become elusive.
 
legrandnormand said:
It could be similar to this coach : http://www.motorhomesusa.com/uholidayrambler05-36neptune-1913-W400.html
Click to expand...

Very very close to this except the one I looked at was a duel slide only.
 
TonyDtorch said:
from everything I hear.....you can just figure an average of about 8-9 MPG in any motorhome,      gas, diesel 3-4-5 or 6 speed.
Click to expand...

Well that would be disappointing, if a diesel got no better mileage then a gas powered unit.
 
  It's not dissapointing when you consider the average diesel pusher weighs in at 25 to 30 thousand pounds,,,my American coach comes in at 26774 and gets an even 10 MPG, I have the 8.3 Cummins, Allison 6 speed and slightly oversized rear tires to get this result.>>>Dan
 
Just plugging in "diesel" doesn't automatically make the mpg better. On an apples-to-apples basis, the diesel will get better mpg than a gas engine doing the same job, simply because diesel fuel has more energy per gallon than gasoline and the higher compression ratio extracts more of it as well.  But that comparison is seldom relevant because the  same coach isn't available with choice of gas or diesel. We can conjecture what a gas engine in that '05 coach might have gotten for mpg, probably less than the diesel, but the only thing that does matter is what the diesel in it actually gets, and that is almost surely in the 7.5-8.5 mpg range. 10 mpg is conceivable, but not many '05 vintage Class A's ever see that.

On the upside, my 2004 diesel weighs in around 37,000 (combined coach and toad) and still gets 7.2-8.4 mpg (depending on  cruise conditions).

A Class C built on the diesel Sprinter van chassis can indeed produce some impressive mpg, but that's not a 36 footer like you are considering. Apples-to-apples it ain't!
 
TonyDtorch said:
from everything I hear.....you can just figure an average of about 8-9 MPG in any motorhome,      gas, diesel 3-4-5 or 6 speed.
Click to expand...

Nope -- not so. My Beaver got 5.5-6.0 mpg. It's a 525 HP Cat C-13 engine with the Allison 4000 tranny, in a 45 foot Monaco Roadmaster Chassis, and weighed a bit over 42,000 empty, rather more the way we traveled.
 
Just plugging in "diesel" doesn't automatically make the mpg better. On an apples-to-apples basis, the diesel will get better mpg than a gas engine doing the same job, simply because diesel fuel has more energy per gallon than gasoline and the higher compression ratio extracts more of it as well.  But that comparison is seldom relevant because the  same coach isn't available with choice of gas or diesel.
Click to expand...

True, true. Many years back I had a chance to discover this for myself. The rigs I drove were all Binders with tandem duals (both rear axles are powered), weighing around 20K lbs empty, and hauling about 20K lbs of (dry) bulk cement or sand. They all came with the International 6 cyl. gas engine, but the company changed some of them to a Jimmy 4-71 (diesel). When filling up after a job, the gas burners typically got about 6 mpg, while the Jimmy's got about 11 mpg. This was consistent over time with several different trucks with each engine.
 
My point was the average 35'-37' class A gas m/h..... and the average diesel/Allison  35'-40' diesel class A m/h.... will get approximately the same fuel mileage.

everyone should already know they are not just the same motorhome with a different motor.

 
I believe the 6 and 5 speed have the exact same first 5 gears.  The axle ratio would be an item to look at. 

The 6 speed will be better if you are one of the MH drivers that cruise at 75-80 mph.  I have them pass me all the time at those speeds even wth toads in tow. ?
 
There is also a bit of confusion regarding the Allison 5 - 6 speeds, and the Allison series model.  My previous rig had a Cummins ISB 6.7 coupled  with an Allison 2500 six speed trans.  While the motor was OK, the 2500 series Allison was terrible.  The 2500 series is a lighter rated trans, and thus has less torque handling ability.  It also has less features, like on board diagnostics from the drivers seat touch pad.

I had constant heart burn with the trans trying to get it to shift and pull grades. It was sluggish to shift, and after cresting a grade it would "hang" in the hill climbing gear, refusing to upshift on the down grade. The RPM's would be exceeding 3000 while the trans wanted to remain in 3rd gear.  When it would shift finally it would slam into the next gear.  I had it to Freightliner several times, only to be told that "it is operating within specs". 

My current rig with the 3000 MH  series Allison is a dream.  It is coupled with a Cummins ISC (680 HP/1050 ft lbs torque).  I believe the 2500 series may be OK in a lighter rig, say in the 30-32' range, but for a heavier coach it is just over matched.
 
Sarge,

I suspect you had a problem with the trans. If I'm not mistaken I have the exact same rig you had, even the same year.  No problems at all with shifting and we get 9.1 mpg with the generator running full time. (Calculated over the last 1,000 miles and cooberated by the computer - allowing 0.1 mpg for the generator).

Ernie

Note that it took about 20, 000 miles for breakin (mileage increased around then).
 
Yeah, I was always certain that there must have been an issue too Ernie. But even Freightliner Gaffney drove it and said it was performing within specs.  I traded it with about 40K on the clock and the driving condition never changed. On the flats it was great, but any kind grade was an issue.
 
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