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Author Topic: Dropbox  (Read 4000 times)
Tom Y
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80 5C With Cummins L10 in Progress




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« on: January 26, 2011, 03:57:37 PM »

Looking to get lower rpms from my engine. I called Rockwell to see if they could point me to a differnt ratio dropbox. I have a 1 to 1 ratio now. They are nice to talk to but they come back with no records found. One lady talked about a .75 to 1 but no more info.  My gear set is an 1986 3.38 ratio. I give them numbers of the gear set, dropbox, rear axle and still no information. Does anyone have a lead on a faster dropbox? Does anyone have an idea what ran these? Will they interchange? Or should I move on? Thanks for any input.  Tom Y
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Tom Yaegle
Lonnie time to go
Lonnie
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« Reply #1 on: January 26, 2011, 05:20:22 PM »

Tom

Is there anyway to post a photo..   Would love to learn as much as possible.
I just have no clue what it looks like. 

Thanks

Lonnie
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1976 4905
luvrbus
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« Reply #2 on: January 26, 2011, 06:08:28 PM »

Tom, the RolliGon marsh trucks used the Rockwell drop box .74 from 1960 to around 1970 I found a few but the gears were robbed from the ones I found.
Also it is my understanding the gears from the dropbox off a Allison has the .74 you can flip the gears and make it work I have not checked on that as I sold my Eagle. 
I can get you a number of a gear Co that cut Bill's gear for his dropbox making it a .93 I'll be seeing him on Friday



good luck
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Tom Y
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« Reply #3 on: January 26, 2011, 07:41:00 PM »

Luvrbus,  Rockwell did mention a box that ran a .93 or so to 1 ratio. I was not intrested as it did not offer enough change.
  I do not think different gears will work. On mine the input and output are the same with an idler gear in the middle. As long as the idler gear is in the same position, the in and out gears must remain the same size.  If the different gear boxes move the idle gear position, and change the other gears. Input more teeth than the output, should speed things up.
  What is a dropbox off an Allison? A tranny with a box mounted to it? Is this the same dropbox us bus people run?    Thanks  Tom
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Tom Yaegle
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« Reply #4 on: January 27, 2011, 05:04:37 AM »

Tom wouldn't it be easier to change the gears in the rear than the drop box.   You could sell the rear now with the 3.36 or just have the gears changed.  Pro Gear in Orlando FL.  would be a good place to talk with.
Jack
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« Reply #5 on: January 27, 2011, 08:18:26 AM »

  Any pics of one of these units you guys could share?
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Tom Y
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« Reply #6 on: January 27, 2011, 12:51:45 PM »

Jack, The 3.38 is the fastest gear I can get. ( As far as I know)

Luvrbus, I looked at some pics of the Allison w/ dropbox. The ones I have seen are completely different.
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Tom Yaegle
Tom Y
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« Reply #7 on: January 27, 2011, 01:28:07 PM »

Heres a pic.
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Tom Yaegle
Tom Y
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« Reply #8 on: January 27, 2011, 01:29:02 PM »

Another
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Tom Yaegle
Tom Y
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« Reply #9 on: January 27, 2011, 01:31:02 PM »

This last on shows the area with the ring and pinion, and the dropbox bolts on.  Tom
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Tom Yaegle
luvrbus
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« Reply #10 on: January 27, 2011, 02:25:31 PM »

Tom, look for one off the old 60 or 70 Allison they were 6 speeds with dropboxes looking at the one on the 700 series they look the same just upside down also check at a Army surplus I was told today the old 6X6 trucks had 2 on the rear the in put shaft ran through the first then to rear but he did not know the ratio but thought it was higher than 1:1


good luck
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« Reply #11 on: January 27, 2011, 06:28:17 PM »

  Thanks very much for the pics, now I can stop imagining.

  Does the engine really sit at an angle??
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Dave5Cs
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1979 MCI MC5Cs 6V-71 HT-740 Allison, Roseville, CA




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« Reply #12 on: January 27, 2011, 06:37:38 PM »

Yes it does. I scanned a picture out of my manual for you too.


Dave
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« Reply #13 on: January 27, 2011, 06:50:32 PM »

On the MCI they are on a angle on the Eagle the engine is offset to the drivers side


good luck
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Lonnie time to go
Lonnie
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« Reply #14 on: January 27, 2011, 07:00:50 PM »

Many many thanks for the photo's
wow i was way off on what it looked like 

Lonnie
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1976 4905
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