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Author Topic: best gear ratio selection?  (Read 3695 times)
robertglines1
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« on: February 18, 2010, 04:53:25 AM »

first of all I have no centersection now....Power will be 60 series or cat C15 with Eaton Auto Shift .73 top gear,4.56:1 was original W/World Transmission...(98 prevost)want fuel economy....Transmission should give me the power for what little hill driving I will do...(have a good deal pending on Eaton  ,maybe with a 60 series)
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Bob@Judy  98 XLE prevost with 3 slides --Home done---last one! SW INdiana
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« Reply #1 on: February 18, 2010, 06:03:43 AM »

Robert, I have the series 60 with Autoshift and have 3.73 gears.  For my driving style it is the perfect combination.  I drive the interstate at 68 and the engine is at ~~1480 RPM.  That is just about perfect for any modern four stroke.  At 62 it is about 1320.  I mention the latter, because of 2 lane driving.  Many are 55 MPH and I have found my setup doing a lot of shifting between 10th and 9th.  In other words, you would not want to go any taller in my opinion.

I often get the truck advertisement papers and about half of them have 3.73 gears.

It sounds like you may be buying the engine and transmission separately.  Be careful here.  The transmission must be able to talk to the engine (exception would be if you run it as AutoSelect) and that requires J1939 communication.  Don't know about non-DDEC engines, but DDEC engines must be DDEC IV.  If you do some research, you will find that DDEC III is supposed to be able to talk to J1939 (must be activated by DD).  However, DD could not get mine activated and I had to upgrade to a DDEC IV ECU ($$$$).

Jim
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Jim Shepherd
Evergreen, CO
85 Eagle 10/Series 60/Eaton AutoShift 10 speed transmission
Somewhere between a tin tent and a finished product
Bus Project details: http://beltguy.com/Bus_Project/busproject.htm
Blog:  http://rvsafetyman.blogspot.com/
robertglines1
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« Reply #2 on: February 18, 2010, 06:14:09 AM »

Jim The pair 60 series were  together(eaton and 60)and operational...
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Bob@Judy  98 XLE prevost with 3 slides --Home done---last one! SW INdiana
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« Reply #3 on: February 18, 2010, 06:22:32 AM »

Robert better check with Rockwell I think you are limited to 3 different ratios on that housing 4:10 being the highest. 

good luck
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Life is short drink the good wine first
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« Reply #4 on: February 18, 2010, 07:22:55 AM »

Robert better check with Rockwell I think you are limited to 3 different ratios on that housing 4:10 being the highest. 

good luck

Clifford, as usual you are probably correct.
But at my last rally he was parked next to a blue/purple and silver Eagle with a yella motor and I saw him and the owner talking more than once! SO he knows who to call if he decides "he wants to make it work! Wink"
Grin  BK  Grin
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Busted Knuckle aka Bryce Gaston
KY Lakeside Travel's Busted Knuckle Garage
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Grin Keep SMILING it makes people wonder what yer up to! Grin (at least thats what momma always told me! Grin)
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« Reply #5 on: February 18, 2010, 08:03:08 AM »

BK, all I was trying to tell Robert is they have 6 different housings and they will accept from 2:93 to 4:88 depending on the axle housing and brake system anything can be done with a torch and welder but why do that when it is available on the open market


good luck
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Busted Knuckle
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« Reply #6 on: February 18, 2010, 08:18:47 AM »

Clifford,
I understand. And all I was pointing out is his current "Prevo" was parked next to Sonny's and may have rubbed off.
Not to mention talking to Sonny has a habit of "inspiring" also. (at least to us easily impressionable types, I know some of you more experienced hands could easily become bored looking at "some of the same ol stuff" Wink
Grin  BK  Grin
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Busted Knuckle aka Bryce Gaston
KY Lakeside Travel's Busted Knuckle Garage
Huntingdon, TN 12 minutes N of I-40 @ exit 108
www.kylakesidetravel.net

Grin Keep SMILING it makes people wonder what yer up to! Grin (at least thats what momma always told me! Grin)
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« Reply #7 on: February 18, 2010, 08:25:05 AM »

As I recall, the MCI has both 3.36 and 3.73 ratios available.  Per my previous note, the 3.73 is perfect for my Series 60/AutoShift.  Some folks have suggested that 3.36 would be better, but that drops the engine RPM down lower that I would like for my 68 MPH desired cruising speed and would almost demand 9 th gear on two lanes.  With the AutoShift you can put it in hold and that locks it in the gear you want (9th for  two lane), but you have to remember to take it out of hold when you slow down and need the trans to shift accordingly.  

If a person looks at the World with double overdrive, then they need a 4.11 if at all possible, or just limit the trans to the first overdrive (which is the same ratio as the AutoShift).

No need to get fancy and replace rear ends unless you go with an HT740 and then you do the Sonnie Gray trick and use 2.93.

Jim
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Jim Shepherd
Evergreen, CO
85 Eagle 10/Series 60/Eaton AutoShift 10 speed transmission
Somewhere between a tin tent and a finished product
Bus Project details: http://beltguy.com/Bus_Project/busproject.htm
Blog:  http://rvsafetyman.blogspot.com/
luvrbus
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« Reply #8 on: February 18, 2010, 08:47:24 AM »

I know BK I would like to have a higher gear I have a lot of different ideas on how to do mine without the drop box but I would never do away with my boggies I love the look of those 
One would be to slide the engine back and flip a truck rear end I have seen a couple of Eagles done that way one with a 3406 Cat and one with 8v92.
Another is to cut different gears for the drop box but the problem I have there is the wife and the cost lol
 


good luck
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« Reply #9 on: February 18, 2010, 09:10:41 AM »

I know BK I would like to have a higher gear I have a lot of different ideas on how to do mine without the drop box but I would never do away with my boggies I love the look of those 
One would be to slide the engine back and flip a truck rear end I have seen a couple of Eagles done that way one with a 3406 Cat and one with 8v92.
Another is to cut different gears for the drop box but the problem I have there is the wife and the cost lol
 


good luck

cost ? ?
Now really? Come on Clifford, Van told me when it comes to your bus or projects cost is no issue! Wink


Grin  BK  Grin









Van yer welcome Wink no thanks required! Grin
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Busted Knuckle aka Bryce Gaston
KY Lakeside Travel's Busted Knuckle Garage
Huntingdon, TN 12 minutes N of I-40 @ exit 108
www.kylakesidetravel.net

Grin Keep SMILING it makes people wonder what yer up to! Grin (at least thats what momma always told me! Grin)
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« Reply #10 on: February 18, 2010, 09:28:55 AM »

BK, Van told you wrong it comes in a package that weighs 130 lbs lol top end speed is not on her list



good luck
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Brian Diehl
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« Reply #11 on: February 18, 2010, 09:50:40 AM »

I am running an ISM with the Gen I autoshift in my MCI 96A3.  My differential is a 3:36 differential.  With my weight ~32,000 lbs ~ I find 55 requires 9th gear and anything over 58 will run in 10th.  However, if there is a heavy headwind then 9th is required.  Once you get over 60 10th gear will do without any problems.  I have some low RPM engine based vibration I try to avoid under higher power levels with my ISM when it runs below 1100 RPMs.  If I were you I would look for the "C" series autoshift instead of the "B" series I have now.  The gear spread is closer in the C series.  This will help you keep the shifts shorter than 500 rpms which is what the B series does.  Of course, you loose the super low 1st gear.  I find 1st nice for creeping around in a campground, otherwise it is not much uses.  I generally start out in 2nd or 3rd depending upon how level the ground is.  I have tested starting out in 4th from a slight downhill and that does work for me.
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robertglines1
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« Reply #12 on: February 19, 2010, 06:53:11 AM »

I like to run 70 to 75 and climb hills (not mountains)without peddling..all the info provided is critical to the final drivetrain selection..economy ,depenability and repair ease are all considerations..yes $$$ are a concern but when you have no present drivetrain..might as well get the best set up for our use...Thank for all the personal experience advice I do respect it all!!!!Bob
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Bob@Judy  98 XLE prevost with 3 slides --Home done---last one! SW INdiana
TomC
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« Reply #13 on: February 19, 2010, 08:17:39 AM »

There are in general two different ratios for the 10 spd Autoshift.  The B model has a 11:1 starting ratio with .75 overdrive, and the C model has a 12.65 starting ratio and a .74 overdrive.  Either will work well, but with the lightweight bus, I would go with the B model.  Also, with the weight of buses being way under the normal 80,000lb that trucks run at, and with all the gears that the Autoshift has, I would ONLY consider the 3.33 gears.  Then with 12R-22.5 rubber running at 485rpm, the 3.33 in overdrive (.75) will give you a 1,514rpm cruise at 75mph-which is absolutely perfect (14-1600 is where a Series 60 should be cruised at).  For maximum mileage, at 55 in 9th gear direct, you'll be turning 1480rpm.  Startability with the B model, weighing in at 60,000lbs (Series 60 produces 1,000lb/ft torque at clutch engagement) will be 27.6%-which is WAY above the 16% startability that Freightliner requires for on road trucks. 
Use the 3.33 and you'll have both performance AND fuel economy. Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #14 on: February 19, 2010, 09:42:01 AM »

Be sure you have your tire sizes in this decision and the tire companies all have good information on their sites.  Then you may want to go to this site and plug in the numbers for what you are seeking.  

http://www.roadranger.com/ecm/groups/public/@pub/@eaton/@roadranger/documents/content/ct_062746.swf

My KW will be running 1300 rpm at 60.8 mph with a 430 hp, 12.7l, Series 60, Gen I 3.36's and .74 O.D.  It originally came with 3.55's and was able to pull 80,000# and at 1300 would be doing 57.5 mph.  That is with 2.75/75 - 22.5's a 40.6" tire.
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Well no longer a bus nut, but over the years I learned a lot here and still come back to see what I can apply to the conversion of my KW T2000 for hauling my Teton fifth wheeler.
robertglines1
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« Reply #15 on: February 19, 2010, 02:14:17 PM »

Stock tire size is 315 80r 22.5 .the new ones are running 365 80 r 22.5  I will do math as will have to buy all new tires and wheels..Thanks again..have 15000 lb front axle.
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Bob@Judy  98 XLE prevost with 3 slides --Home done---last one! SW INdiana
RJ
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« Reply #16 on: February 19, 2010, 06:22:28 PM »

Robert -

Not sure if you are aware of this, but TomC sells trucks, medium & heavy-duty Class 8 rigs.  In so doing, he is constantly putting together powertrain combinations to fit particular applications for his customers, and has lots of tools available to do so.  So he's a great resource to help guide you to obtain the best bang for the buck.  Might see if you can come up with the revs per mile for the 315 or 365 tires you're contemplating, to help him give you more accurate suggestions.

Are you planning any jaunts to the West Coast?  If so, do NOT expect your bus to climb the grades we've got out here like your car does.  Unless you've got over 800 hp pushing you along, figure you'll be pulling grades between 35 - 45 mph with most standard bus powertrains.  Lots of busnuts are shocked to find out their bus will not go up the mountain at 70+ mph like their Chevy, Ford, Honda or Toyota will.  It's called mass!

An example of our grades:  I-80 between Sacramento CA and Reno NV has over 70 MILES of 4, 5 & 6% grades, climbing to 7300 feet.  And, of course, you've got the infamous Eisenhower Tunnel on I-70 outside Vail, CO that's at the 11,000 ft level - wheeze city, even for the turbos!  So even if you've got it set up properly for decent fuel economy rolling across the midwest, it's going to fall flat on it's face going over RockyTop West. 

Just a little reality check for you.

FWIW & HTH. . .

 Wink

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RJ Long
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robertglines1
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« Reply #17 on: February 21, 2010, 05:09:50 AM »

Our basic use will be midwest with occasional trip west of mississippi..I do have patients because my first coach was a 8v71 hound..Maybe Airzona for next winter...
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Bob@Judy  98 XLE prevost with 3 slides --Home done---last one! SW INdiana
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« Reply #18 on: February 22, 2010, 10:03:37 AM »

When regearing-remember-if you have only a 4 or 5spd manual transmission, your cruise speed is not the issue.  The issue is startability (the ability to start on a grade, or to be able to back up a grade).  Most buses with stock engines and 4 speeds have very poor startability.
If you want to figure your own startability, first take the total weight of your rig (including a towed or trailter) and multiply that figure by 10.7-and put it into memory.  Then take the starting torque of the engine (on a manual transmission it will be about 2/3 the rated torque, on an automatic, the full torque since the torque converter allows the engine to rev up into the torque curve), multiply that by the torque converter multiplication (this only applies to torque converter automatics-typically 2 to one), multiply that by 1st gear, multiply that by the rear end ratio, multiply that by the tire revolutions per mile, and divide the whole thing by the weight figure that is in memory.  You'll come up with startability in grade percentage.  For instance, Freightliner wants at least a 16% startability for over the road trucks, and at least 24% for on/off road.  Just something fun to play with.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #19 on: February 22, 2010, 10:12:05 AM »

For instance, on my bus, I weigh in at 34,750lbs-multiply that by 10.7 and put it into memory (371,825).  Take engine torque (1,175), multiply that by torque converter ratio (2.65 on V drive), multiply that by first gear (1.77), multiply that by rear end ratio (4.56), multiply that by tire revolution (476) and I come up with 11,962,688. Divide that by the figure in memory and I come up with a little over 32% startability-of which I feel confident on never getting stuck, since I have never seen a grade over 20% (typical interstate is 6%, sometimes maybe 8%).  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #20 on: February 22, 2010, 10:41:49 AM »

I came up with 10.6%.  Interesting calculation!

Brian
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1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
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