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Drop Box Overdrive Gears

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Drop Box Overdrive Gears
Fri Jun 05, 2009 5:15 pm


Several years ago I had a great gear cutter lined up to build a set a gears that would make the drop box into an overdrive. As I recall, we had drawings and thought it was doable. I asked to see if anyone would would furnish a drop box for the project and did not get any volunteers.

Last year, I talked to Bill Stoner and he said that he had a set of gears made for his beautiful bus. I did not get any details.

Now, Clifford mentions that he is working on this project in another thread.

I am starting this thread in hopes that folks will chime in with information/details.

I don't need it for our bus, but folks doing a conversion to a four stroke with an HT740 could sure use this modified box.

Jim
Jim Shepherd
Evergreen, CO
'85 Eagle 10 with Series 60 & Eaton AutoShift 10 speed transmission - not at all fancy, but fully functional
Bus Project pages: http://beltguy.com/Bus_Project/busproject.htm
Blog: http://beltguy.com/blog/
Email: jim@eaglesinternational.net (Please email me rather than use the PM process)
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beltguy
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Re: Drop Box Overdrive Gears
Fri Feb 19, 2010 1:57 pm


Too bad no replies...seems like a worthy topic.
DaveG
 
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Re: Drop Box Overdrive Gears
Fri Feb 19, 2010 2:26 pm


Dave, the cost is a big factor the best price I could find for cutting and the heat treatment was 4 grand for 2 gears.
Bill has a 855 Cummins- 625 hp built by Penn Diesel he really needed taller gears so he done it as he wanted to keep his boogie axles.
Fwiw I check every drop box I find off a Allison trying to get lucky and find one that beats the 1:1 ratio .


good luck glad your here
Clifford
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luvrbus
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Re: Drop Box Overdrive Gears
Sat Feb 20, 2010 11:38 am


luvrbus wrote:Dave, the cost is a big factor the best price I could find for cutting and the heat treatment was 4 grand for 2 gears.
Bill has a 855 Cummins- 625 hp built by Penn Diesel he really needed taller gears so he done it as he wanted to keep his boogie axles.
Fwiw I check every drop box I find off a Allison trying to get lucky and find one that beats the 1:1 ratio .


good luck glad your here
Clifford


Thanks Clifford. Appreciate you. Enjoyed watching the video of you tuning Van's 6V
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Re: Drop Box Overdrive Gears
Sat Feb 20, 2010 12:44 pm


Clifford, it sounds like you think there is a possibility that there be a dropbox that has an overdrive.

On the BCM board, there is a thread on gearing (think you were involved) and Ed Hackenbruch talked about his MCI 5 being able to do well over 80 with what he thinks is stock gearing. Ed and I have talked quite a bit about it, and I think he is giving good numbers. He has checked his speed with GPS and timed highway markers. He has not checked his tach, but it sounds to be correct. He says he has two MCI 5 friends who get the same results.

So, this begs the question as to whether MCI might have made an overdrive dropbox. I can't imagine why, but the "facts" are strange.

Jim
Jim Shepherd
Evergreen, CO
'85 Eagle 10 with Series 60 & Eaton AutoShift 10 speed transmission - not at all fancy, but fully functional
Bus Project pages: http://beltguy.com/Bus_Project/busproject.htm
Blog: http://beltguy.com/blog/
Email: jim@eaglesinternational.net (Please email me rather than use the PM process)
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Re: Drop Box Overdrive Gears
Sat Feb 20, 2010 1:17 pm


Do I understand the the dropboxes were from Rockwell? Was there any other application that these were used that might have different ratios?
DaveG
 
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Re: Drop Box Overdrive Gears
Sat Feb 20, 2010 1:45 pm


Dave, a lot of drop boxes are in use today in military and the air ports handlers equipment.
The guys at Palmer Johnson Power tell me there is a .73 out there used with a Allison with the drop box www.pjpower.com goes by the name AxleTech still a divison of Rockwell.



good luck
Clifford
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Re: Drop Box Overdrive Gears
Sat Feb 20, 2010 2:09 pm


Wow. If there is a .73, that would be the perfect solution for folks wanting to use an HT 740 with a four stroke.

Would bet it would be a ton of money. If the case has the same shaft layout, then the challenge would be to find the gears for the .73 box.

That would also explain Ed's numbers reasonably well. If 72 MPH is about correct for tires with ~~490 revolutions per mile/3.73 rear end/2100 RPM, then a .73 would give you a calculated speed of ~~ 98 MPH. That would be a little tall for Ed's numbers, but in the ball park.

Jim
Jim Shepherd
Evergreen, CO
'85 Eagle 10 with Series 60 & Eaton AutoShift 10 speed transmission - not at all fancy, but fully functional
Bus Project pages: http://beltguy.com/Bus_Project/busproject.htm
Blog: http://beltguy.com/blog/
Email: jim@eaglesinternational.net (Please email me rather than use the PM process)
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beltguy
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