eaton, rockwell, fuller transmission swaps

[kyle4501]

With fuel costs consuming more of the travel budget, I'm re-thinking my hot rod attitude of the BIG ENGINE to the top of the mountain in high gear attitude. 

So, if I'm gonna stick with a lower HP engine to minimize fuel useage, I'm gonna be leading more parades up the hills & mountains.   

I'm OK with that, but I think I might like having more gear ratios to choose from while going up those mountains. Having lower gear ratios in the campgrounds wouldn't be all bad either. 

Now the question/ request:
For those that have installed transmissions with more gears to chose from, could you share in this thread what you learned? (I've searched & can't find much)
Links to other threads are good too. 

Bus year & make and the engine/ transmission installed PLUS what other changes were required (bulkhead modifications & etc).
A critique of the process, effort required & end results (road test) would help others decide what best fits their needs.

THANKS!

[JohnEd]

Kyle,

Physics says that to go up a hill faster takes more energy.  So faster means less MPG.  That is an immutable law.  While other factors come into play those statements are always accompanied with "all other things being held constant".

A man I deeply respected once told me that the max efficiency of a gas engine was found at wide open throttle.  I recently pondered that and I guess a diesel is running at WOT by design.  Still, I think a smaller engine gets better MPG.  The funny thing, to me, is that a smaller engine and a larger one should have the same fuel flow to maintain the same speed as long as the speed was low enuf for the small one to achieve.  It doesn't seem to work that way though and I don't think a heavy foot is all the answer.

A Knut with a new newly installed Cummins M11 is getting 12 MPG with the norm being 10 plus.  Another with an ISM is getting high 8 but that will be 9 plus in time.  Road ranger 10 speed seems to be the ticket regardless of the engine as "Bob of the north" gets 8 plus with a 500hp 8V92 and a nine speed manual (go figure).  Now Bob is nothing short of delighted with his Prevost bus and well he should be.  Most of the 8V92's are getting 6 or 7 with some getting 3(brrrr).

None of this is my personal experience but i have talked with many on the subject.  What i am saying I guess is that these are not my own persoonal lies....I'm just repeating them

Hope this helps,

John

[kyle4501]

The statement "faster means less MPG" assumes the efficiency of the engine is constant regardless of RPM.

Most engines have an efficiency curve, hence the desire for more gears to allow one to operate the engine at it's most efficient RPM. As a result, better fuel economy can be observed & probably, more fun driving it.

I didn't mean to imply I still wanted to be the fastest up the hill. I meant top say I was OK with going slower & that I wanted more gears to do it with.

Also, a tranny swap may be more cost effective than a total repower.

4 speeds may have been enough for greyhound, but I ain't greyhound & I don't park at bus depots. 


Several friends have mentioned more gears & I just thought a thread discussing the pros & cons of different setups would be easier for those researching the possibilities.

[Jeremy]

Kyle - I assumed at first you were wanting more gears to enable a smaller engine to get up the hills; now I'm not sure if that was what you meant, so the following comments about fitting smaller engines may be irrelevant, but I've already typed it so will post it anyway:


Obviously some engines can produce a given amount of power more efficiently than others, due to design & technology differences - but, leaving those differences aside, the same vehicle fitted with a smaller engine won't use any less fuel unless the driver uses less engine power - which of course he might have no choice about if the power isn't available.

A good way to convince yourself of this is to look at the sales brochures of any car range - for example, if you look at the specs of a Ford Fiesta fitted with the various different engine options you will see that the economy figures are broadly speaking very similar irrespective of engine capacity. Then look at the Ford Focus and Mondeo models (ie. progressively larger vehicles) fitted with exactly the same engines you will see that the economy drops as the weight and size of the vehicle increases, but still remains broadly similar across the range of engines.

Obviously, when producing the economy figures for the various Fords each car was driven in a very efficient and economical manner, which is probably quite different to the way they are driven in real life when it is only natural to make use of the power that is available. Nevertheless, if unless you are switching to a much more modern and fuel-efficient design of engine I'm not sure reducing engine capacity for the sake of it makes much sense.

Jeremy

[Bob Gil]

From my driving for the last 30 something years.  I have seen many trucks on the road with the Small engines and multi shift tranys that you could out work a bigger engines with if you knew how to use the choice of gears to your advantage.

I know that the old Pete I drove had a 400 cumins in it with a 5x4 transmission and 4.33 rears was a bear in town but when loaded it would do the work of a bigger engine.  The more gears the easier it is to keep it in the choice RPM area.

I don't think you would want a two stick in a bus but a 8 or 10 speed might not be too bad.

Myst my worthless thoughts.

[kyle4501]

Thanks Bob, That is what I was trying to say - more gears let a small engine work more efficiently 

[boogiethecat]

Here's my experience... for the situations I've encountered, it just doesn't matter.

I bought my Crown and with it came with it's 220hp engine and the factory 4 speed.  I got 10mpg and it took 6% grades between 30 and 35mph.  But my top speed was 61mph due to the crappy rear end gearing.

I then changed the tranny to a Fuller 9 speed with overdrive and other than the fact that virtually nobody could figure out how to shift it but me, it still got 10mpg and still went up those same grades at the same speeds.  Top speed was now around 78. Cool!!

I got tired of shifting the 9 speed grinder (because I was now the only driver on long trips), so I put in a nice shiny Eaton fully synchronized 6 speed.  At the same time I changed my rear axle to accomodate a Telma retarder, and the rear end ratio changed from 5:29 to 4:11.  It was perfect, still went up the grades at the same speeds and got 10mpg, but being that the tranny was not overdrive and the rear was still a bit high, my top speed reduced to 69 which I didn't like.

So last but not least I found an Eaton FSO8406A which is the fully synchronized 6 speed with overdrive, all the other ratios are different than they were in the non-overdrive Eaton, and now my top end is back around 78 or so, and guess what... still the same speeds on the same grades and 10mpg.

So while I originally thought from all I'd read that having all those gear choices made a big difference, at least for this bus it didn't make ANY difference.
I absolutely LOVE the 6 speed overdrive, ANYONE can now drive the bus, mileage is the same, time-to-destination is the same, etc.

My 2ç worth...

[HB of CJ]

I do not know if a RTO 910 will fit in your 4501, but if it will, then that is the 10-speed Roadranger you want.  Also do not know what kind of mill you have, however the RTO-910 has very close gears and was practically designed for the 318 8V71N.

About the only other thing I can think of is that the Fuller RT/RTO/RTOO 910/1150 series of Roadrangers are now kinda very old and may or may not be easily available at your local, friendly heavy truck wrecking  yard.  Most may have been recycled.

However, if you can find one, expect to pay about $1000 bucks (US) for a good runner complete and about $1500 to $2000 for a rebuilt unit complete with warrantee.  A good core for rebuilding yourself can be had for only a few hundred bucks or soosss.

Why a RTO-910?  Well, for those who like to know this kind of stuff, the gear sets are...about... 1st, 6.27, 2nd, 4,98, 3,95, 3.13, 2.57, 2.00, 1.59, 1.26, 1.00 and .82.  Yeah, very close together indeed.  Perfect for a somewhat underpowered Bus Conversion.

My old Crown Super Coach had this particular transmission.  Perfect starting from stop up one of those steep, endless, Western grades of 6% or 7%.  More like shifting a dirt bike than a heavy truck tranny.  About 2" of shifter movement and 5# of effort.

In my humble opinion, you may want to stay away from the more modern and available 9-speed Roadrangers.  They have kinda wide, low gears that would be wasted in a light weight Bus Conversions.  This type of tranny is designed for heavy hauling.

Anyway, I usually started in 2nd and progressivlely shifted up and before I knew it, the old Crown was at cruising speed.  Very easy to keep the rpm between 1700 and 2100.  At 55 mph, I had a choice of 3 gears, 8th, 9th, and 10th.  Very cool.  Good luck. 

[buswarrior]

HB hits the nail on the head:

You want a tranny with overlap and choices at the top, for hill climbing.

It doesn't do any good to fit a new transmission that still has to wait for the speed to drop to 50 mph for the first down shift as the hills rise ahead of you.

no one suggesting a 13 speed? An Eaton Ultrashift 13, no clutch pedal, would be fun to pair up with the right differential...

happy coaching!
buswarrior

[kyle4501]

Now we're getting somewhere.
It seems to me the overlap would make selecting the right gear so much easier.

I also like the Ultrashift idea, but I need more info 

I believe my 4501 can handle any transmission if the bulkhead has the necessary preparation. It also has a 3.70 ratio axle.

Thanks ! ! !

[RJ]

Kyle -

OMG - you're going to. . . going to. . . going to. . . going to cobble up the powertrain on the hallowed Scenicruiser?

Is there no justice left in this world?





On a more serious note:

IBME, after 25+ years in the bus industry, is that the weight of the coach, the aerodynamics of the coach, slushbox or stick shift, and the weight of the operator's right shoe are the three major components of good (for a bus) fuel mileage.  Just like cars, sticks get slightly better mileage, but as efficient as the newer automatics are, it sometimes becomes a moot point.

Weight is the killer - takes HP to get rolling and keep it rolling.  "Build the interior out of balsa wood, not oak & granite" type of thinking, if you will.

I loved playing with all those gears in the 10-speed RoadRanger-equipped Crown skoolies. . . but also often got tired of going thru seven gears just to get to 35 mph.  90% of the time I drove them like 5-speeds by skip-shifting, as did most of the other drivers in the district.

And they still went up the 6% grades at 35 mph. . . 

With the MCIs in the fleet I worked at, the sweetest, IMHO, powertrains were in the 9s that had the 8V71Ts bolted up to HT-754 five-speed Allisons.  Tuned to just 350 hp, with the stock 3.73 rear axle, they would often get 7 - 7.5 mpg when the 8V71 and 6V92TA coaches were getting 5.5 - 6.5 on the same runs.

One thing to keep in mind, if you go to almost any of the mechanical multi-speed RoadRangers or similar, is the shift pattern.  Unless you do some clever engineering, you'll end up with a backwards shift pattern, since the transmission is "turned around" in a pusher configuration compared to a truck installation.  (Shift it "normally" and you'll have 10 speeds in reverse!)

IMHO, if you're going to follow thru with this project, I'd suggest you try to find a truck with an Cummins ISM coupled to an UltraShift  (or a Series 60/UltraShift) that's been wrecked, and buy the whole truck.  That way you can get all the wiring harnesses and other the other goodies needed.

TomC should be able to help too, as he sells Class 8 rigs and deals with powertrain configurations daily.  Tom - where are you??

OTOH. . . you could leave it stock - how many millions of miles did they run that way??? 


FWIW & HTH. . .

[belfert]

Isn't the Ultrashift completely computer controlled?  I know the Autoshift can be linked to a machanical engine with an interface, but no idea if the Ultrashift has this option.

[Ncbob]

Kyle, knowing that you're A) an Engineer and B) a bloomin' nutcase perfectionist, I'm going to throw my $0.02 in here and ask you to spend some time with your Engine/Transmission package before you go off chasing butterflies.

I've been pushing this MC5A with the DD8V71 / 4 speed Spicer package up and down the roads for over 2 years now and have come to this conclusion:

Between the Engineers at MCI and the Bean Counters at Greyhound (and others) someone definitely had their act together. For that era, remember the choices of engines and trannies we have now didn't exist then, this was the best package available....and in my opinion still is. I'm not the first one up the mountain (on those rare occasions I tackle them...and we LIVE IN the mountains) and I'm the last one down, even with Jakes. But when I consider the cost and labor in attempting to improve what I have...re: Boogiethecat, as against what I hope to achieve I believe I'd be shoveling $hit against the tide.

Sure, I'd like a slower reverse gear...but can live with what I have rather than re-engineer the whole package.

I have some miserable places I have to stick this ol' bus and do it quite well considering my experience (or lack thereof) and power options.

FWIW

Bob

[TomC]

The only thing changing from a 4 spd to a 9 or 10 spd will get is a lot more shifting and maybe 3-5 more mph on the hills-sometimes it will be the same if the torque/speed matches the same gear in either trans choice.

My advice-forget the trans swap.  If you want maximum change in both fuel economy and performance, turbocharge and air to air aftercool your 8V-71.  I did and I can tell you from experience, that the performance difference is quite noticeable.  Granted I increased my power also, but you could keep the 65 injectors for a fuel efficient 8V-71.  You would probably see 2-3 more mpg and better hill climbing.  With the low mileage that most of us drive our buses, turbocharging rather than engine swap is much more cost effective.

But with the room of the 4501, a Cummins ISM with a 9 spd (I like the shift pattern of the 9 better than the 10), would be ideal.  Good Luck, TomC

[Dallas]

My two cents worth..... (and this is with the caveat that I've only put in 3.5 million miles of driving truck, mostly heavy haul in a 30 year time frame).

Even though I am a hard core, tried and true, true blue, through and through, GMC - Detroit Diesel Afficianado, I detest the high gearing on the lower gears of the coaches, whether it's GMC, MCI, Flxible, TMC, Eagle, Prevost or any other manual shift transmission. The buses were built to go from stop to stop and terminal to terminal. Once in awhile, they would see a shop, but not nearly as often as they really should have.

My choice, if I were going to keep the Scenic all mechanical and stay away from the computer controlled doodads, would be a nice "Shiny 290" or 335 Cummins hooked to a RTOO 9513 Road Ranger. If I wanted HP, I'd stick a NTC 400 BCIV Cummins  with a RTOO 14613 Road Ranger.

Either one I would couple to a Mack 4.38 or 4.56 rear end. Driveability would be excellent, the rpm range with 20" or 22.5" rubber would be in the sweet spot for climbing and also for getting into tight uphill reverse situations.

There is no law in the world that says you have to shift through every gear, in fact, most of the companies I ever worked for would consider you to be abusing equipment and wasting fuel if you did. All those gears are there to allow you to choose the very best combination of power, RPM and driveability to move the load with decent return on the parts.

NCBOb said:

I've been pushing this MC5A with the DD8V71 / 4 speed Spicer package up and down the roads for over 2 years now and have come to this conclusion:
Between the Engineers at MCI and the Bean Counters at Greyhound (and others) someone definitely had their act together. For that era, remember the choices of engines and trannies we have now didn't exist then, this was the best package available....and in my opinion still is. I'm not the first one up the mountain (on those rare occasions I tackle them...and we LIVE IN the mountains) and I'm the last one down, even with Jakes. But when I consider the cost and labor in attempting to improve what I have...re: Boogiethecat, as against what I hope to achieve I believe I'd be shoveling $hit against the tide.
FWIW
Bob

I have to respectfully disagree. These buses were built to move at a decent clip up hill and down, not to be backing and filling up an incline from a dead throttle start. Terminals and stops and shops were never on an incline. Remember the debacle of my trying to climb the hill into your campground when the idjit decided he was gonna come down after I had already started up? I not only ran out of power, but I was burning the clutch trying to make my 26K lb. bus move.
The engineers were working with the parameters that Greyhound, Trailways and a multitude of other companies gave them.
The spicer transmissions were one of the cheapest to build and at the time the MC5 was built, a clutch could be changed for less than $300 parts and labor included.

The whole idea behind the way these buses were set up was to be cheap and reliable and quick to fix to get back on the road. Trucks are somewhat different.. with a truck you never know what kind of load you'll be carrying, 8,ooo pounds or 48,oooo pounds. With a bus, it's a bit different, the companies knew they would not be hauling more than 35, 37, 41, 43, 45, 47, etc. passengers and a bit of freight and luggage. Even the vaunted claim of 4 - 8V71's in the bays of the Scenic would only be 10,000 pounds, with 45 passengers @ 160 lbs each, only adds another 7200 lbs. Add to that the luggage, you still end up with less than about 20,000 lbs. of load. On the runs these buses were put on, their gross weight really had no bearing on the driveability of the bus. Our actual use is much more demanding for these coaches than the intent and purposes ever thought of by the hound or TW.

Just one more item here... I've not seen it mentioned in any thread or post on any board... Progressive Shifting

To gain maximum fuel mileage, the idea is to shift as soon as the engine will pull it without lugging. That means that you don't need to go to the top of your governor if you are starting out on a downhill slant, or even if the road is level. As you go up in the gears, it will take more RPM's to get to the next gear, hence the "progressive" part.

I've been asked how I can achieve 13mpg with my PD4103 and my answer is always, "Shift Progressively". No need to make the engine catch up to the speed of the wheels if it's on a no load start. I shift up through my gears as quickly as possible. For instance, if the speed limit is 35 mph, I know that my transmission is geared so that I will be in 3rd gear at about 1800RPM, but, if the terrain is flat or slightly downhill, I go ahead and shift into 4th since there is no real load on the engine and I can drop back to 1100 RPM. As soon as I see a hill coming up, I can shift back down to 3rd, which puts my transmission back into the power range of 1600 to 1800 RPM. No need to wait until I've started climbing, I try to always look ahead at least a half mile and usually on open road one or two miles.

'Nuff Said.

Dallas