BCM Community

Bus Discussion => Bus Topics ( click here for quick start! ) => Topic started by: NeoplanAN440 on April 12, 2010, 05:14:36 PM

Title: Rockwell Gear Ratio change or complete Axle flip
Post by: NeoplanAN440 on April 12, 2010, 05:14:36 PM
Collecting all the bits and pieces for the Cummins repower,im trying to find out if there is a way to change only the gears or complete pumpkin on my axle!?
otherwise i would have to flip a semi axle!

the only #s i could find on my stock axle are

59743WX19    NK8361995

are there any good axle shops in the AZ or CA area that can help,or maybe a internet site to cross my numbers to see if there is a pumpkin or gear set that would fit!!

i would like to keep my stock pumpkin,in case i ever go over to a b400 or b500 tranny!

Title: Re: Rockwell Gear Ratio change or complete Axle flip
Post by: TomC on April 12, 2010, 10:35:49 PM
What gear ratio do you have now?  The simplest and cheapest would be just to go with an Allison World transmission now with your engine exchange.  Since you have an HT748 now, which is a direct drive 4th gear. With the World transmission, you have a .74 5th gear and a .64 sixth gear.  So that means when you're at top speed in 4th gear at 2100rpm, when you shift to 5th, you'd be at 1554rpm and with 6th at 1344rpm.  Even if you had only a 55mph top speed now, your top speed would be 86mph with 75mph cruise at 1832rpm-sound good to me!  Good Luck, TomC
Title: Re: Rockwell Gear Ratio change or complete Axle flip
Post by: NeoplanAN440 on April 13, 2010, 07:07:19 AM
my stock ratio is 4.63

yes im going 55 at 2100 with that axle,and i have the governor turned up to 2400 for "THESE" traffic situations that come up!

i had planned to keep this axle or pumpkin,for the event i can find a b400 or b500,with the parts needed to run a mechanical L10.
right now im looking into using a roadranger 9 speed,but havent found all the pieces,to fabricate the shift linkage and clutch setup.
if i find a "cheap and good" world transmission first,i maybe go that route!

i like to keep things mechanical and easy to service for me,but if the manual transmission swap shows to many problems in the going,i may go with the world transmission and keep a spare.

the bus is only a hobby and a way to get out and travel.i try to keep the costs for it,and risk of a breakdown in my budget.which means i need to be able to fix things on my own,even when im on the road far from home!!
that  explains why i keep a spare engine and transmission,ready in the cradle to slide in.
even if i have to do it on a parking lot somewhere.

thats just me!
Title: Re: Rockwell Gear Ratio change or complete Axle flip
Post by: TomC on April 14, 2010, 04:31:17 PM
I know on my Kenworth cabover, the shifter was cable connected to the transmission to easily allow the cab to tilt.  While the shifting was a bit stiff, it wasn't too bad.  Course, I don't know if they can make nearly 40ft cables that will work compared to the 8ft cables on my truck.  Good Luck, TomC
Title: Re: Rockwell Gear Ratio change or complete Axle flip
Post by: NeoplanAN440 on April 15, 2010, 03:10:24 PM
I also found a shift tower for a cable operated shifter.they told me its from an international.
im a little worried how it will perform,as you say,almost 40 feet and a loop to correct the shifting to normal!

im now working on a single shift tube idea,with u joints as connectors.
found a tube shift tower from a cabover.
i was going for a roadranger rto910 ,but found a rtx11710c.have to check the specs,but believe its
0.72 in overdrive and has the corrected shift sequence!

people told me there is a rtoo910,but i never found one.whats the ratio of the second overdrive?

maybe just with the overdrive transmission mated to the l10 i get away without changing gears.
the l10 can do 2100rpm,just have to see how it works on the long run.

then there is the idea with the b500 !!! but that means i have no control over the shifting,kind of how i fell with my ht748 now.
Title: Re: Rockwell Gear Ratio change or complete Axle flip
Post by: belfert on April 15, 2010, 03:57:41 PM
I suspect cheap and good are two things you'll never see with a B500. 
Title: Re: Rockwell Gear Ratio change or complete Axle flip
Post by: NeoplanAN440 on April 15, 2010, 05:24:58 PM
thats the point with a 500!

Title: Re: Rockwell Gear Ratio change or complete Axle flip
Post by: TomC on April 15, 2010, 07:26:57 PM
Typically the RTO-910 has about a .75 overdrive.  The RTX-11710C has a .73 overdrive.  The first version of 13spd is a 9spd direct transmission with a .86 overdrive auxiliary.  The second version of 13 spd was a 9spd overdrive transmission with an .86 overdrive auxiliary.  This gave a .86, .73, and a .63 overdrive.  Current 13spd and 18spd (the only difference is that the first 5 gears can be overdrive split with the 18 but not on the 13) have a 9spd overdrive transmission with a .86 underdrive auxiliary.  These transmissions have a .86 (which is the underdriven overdrive of the transmission) and .73 of the transmission.  Confusing. Good Luck, TomC
Title: Re: Rockwell Gear Ratio change or complete Axle flip
Post by: NeoplanAN440 on April 16, 2010, 07:59:00 AM
little confused!!  YES!!

what manual transmission would give me 0.63 overdrive?????

that would take away the need to change rear ends!!!
Title: Re: Rockwell Gear Ratio change or complete Axle flip
Post by: TomC on April 16, 2010, 08:53:18 AM
If you could find a RTOO-12513.  They were rather rare though.  Good Luck, TomC
Title: Re: Rockwell Gear Ratio change or complete Axle flip
Post by: DaveG on April 16, 2010, 05:13:18 PM
At some point driveline speed could become an issue with an overdrive ratio like that.
Title: Re: Rockwell Gear Ratio change or complete Axle flip
Post by: TomC on April 16, 2010, 10:53:04 PM
Driveline speed can be an issue. But the drive shaft on a bus is short, and Meritor usually wants to keep the driveling rpm down under 3,200rpm-which in the case of the 4.63 with 12R-22.5 tires-that would be around 85mph.  So I don't think driveline speed is going to be a problem here. Good Luck, TomC