best gear ratio selection?

[robertglines1]

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)

[rv_safetyman]

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

[robertglines1]

Jim The pair 60 series were  together(eaton and 60)and operational...

[luvrbus]

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

good luck

[Busted Knuckle]

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! "
  BK 

[luvrbus]

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

[Busted Knuckle]

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"
  BK 

[rv_safetyman]

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

[luvrbus]

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

[Busted Knuckle]

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!


  BK 









Van yer welcome no thanks required!

[luvrbus]

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

[Brian Diehl]

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.

[robertglines1]

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

[TomC]

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

[NEO/Russ]

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.