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Author Topic: Dropbox  (Read 3939 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
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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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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
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« Reply #7 on: January 27, 2011, 01:28:07 PM »

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

Another
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Tom Yaegle
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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
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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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« 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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« 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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« Reply #15 on: January 27, 2011, 08:40:23 PM »

   So the back of the engine is centered with the bus, pointed toward the drop box? Isnt that hard on the U-joint??

   On that drop box, can that front cover be easily removed to see inside at the gears for rust???
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RJ
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« Reply #16 on: January 27, 2011, 10:59:02 PM »

Paul -

MC5 engine, transmission and driveshaft are all in a straight line, but sit in the chassis such that the rear axle end of the driveshaft is approximately 4" > 6" to the left of the coach centerline.

To help you visualize this better, sketch a right triangle, with the base 90o angle looking like a capital "L".  Turn the drawing around so what was the top now points down.  The engine crankshaft pulley that drives the squirrel cage blowers is the bottom point of the triangle.  The forward-facing pinion shaft in the differential is in the same plane with the engine crankshaft pulley, forming the vertical side of the 90o angle.  The drop box forms the base of the triangle (which is now at the top as it's turned around.)  The engine block, transmission and driveshaft form the hypontenuse of the triangle.

Hopefully the attempt below will help with the visualization!

FWIW & HTH. . .

 Wink 


|\
| \
|  \
|   \
|__\

___
\    |
 \   |
  \  |
   \ |
    \|



Whew!   Cheesy
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RJ Long
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« Reply #17 on: January 27, 2011, 11:28:37 PM »

  Okay, I'll admit you lost me there a little bit. Its truly amazing how little information is out there on the web about these -5's, compared to other coaches like 4104, 06's, etc.. I cant even find a picture of the back with the doors open, much less a pdf file for manuals, been ridin the web til my eyes are bloodshot.

  I saw the input flange for the drop box, with the drive shaft coming at it, it looked straight to me, which is why I was curiious about the layout when someone said the engine was angled. I guess it really dont matter a lot, it is what it is, I was just trying to visualise it in my head.

  It sounds to me what your saying, is the engine and gearbox are centered in the chassis, running perfectly straight forward amidships, just like any other MCI, and the differential (pumpkin) is offset to the right, and the drop box come's up at an angle to the Bus centerline to meet the forward running driveshaft which comes over the top of the axle and plugs into the drop box. If I still have it wrong just shoot me.

  So, can I pull that cover off the front of the drop box and look inside for rusty gears, or are a whole bunch of spacers and shims and other important little bits going to fall out in the dirt and get lost.

 
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bevans6
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« Reply #18 on: January 28, 2011, 05:28:36 AM »

ask and ye shall receive...  Pic of the back of a 5C with the doors both open and closed...  Of course, the one with the doors open has an engine in the way... sorry about that!

Brian
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« Reply #19 on: January 28, 2011, 05:34:41 AM »

\here is one showing the transmission, 4 speed Spicer and the belt drive DN50 alternator.  from the other side showing the gearbox, the compressor and the power steering pump, if you look really closely.  You can also see the engine cradle that slides onto rails in the engine bay.

Brian
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Spicer 8844 4 speed Zen meditation device
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1972 NTM MK-4 B/SR
Ed Hackenbruch
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« Reply #20 on: January 28, 2011, 06:10:29 AM »

You need to go look at a 5 to really see it.  Open the doors, stick your head in a bit and look straight down at the bottom pulley. You will notice that the left side of the pulley is a little closer to the bumper than the right side is. Grin
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RJ
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« Reply #21 on: January 28, 2011, 09:33:23 AM »

Paul -

It sounds to me what your saying, is the engine and gearbox are centered in the chassis, running perfectly straight forward amidships, just like any other MCI, and the differential (pumpkin) is offset to the right, and the drop box come's up at an angle to the Bus centerline to meet the forward running driveshaft which comes over the top of the axle and plugs into the drop box. If I still have it wrong just shoot me.

Where's the gun?   Grin Grin Grin


Seriously, go back and re-read what I said, and look at that little pictogram of the upside-down right triangle. 

Remember your geometry?  The Hypotenuse is the side of a right triangle opposite the right angle.

The engine's crankshaft, the transmission, and the driveshaft form the hypotenuse.

The dropbox is the horizontal base of the triangle.

The centerline of the bus, the pinion input shaft of the differential, and the big bolt that secures the harmonic balancer onto the crankshaft form the straight vertical side.

You do have it correct that the driveshaft goes over the top of the axle, and it does so on the driver's side of the ring & pinion pumpkin.  The pumpkin is NOT offset to one side - GM did that, not MCI & Eagle.

This isn't a very wide triangle - we're only talking about a 4" - 6" offset over a 3' - 4' run between the back bumper and the U-joint on the dropbox.  It's certainly not enough to cause excessive strain on the U-joints due to the small angles they have to run.  I've seen much more severe on some of the ag equipment around here.

Oh, just to keep you confused, Eagles that use dropboxes are also angled this way.

May be hard to picture in your mind, but it's very obvious when you are standing at the back of a coach with the engine compartment doors open.  (Doesn't photograph well, tho.)

Clear as mud yet?

FWIW & HTH. . .

 Wink
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RJ Long
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« Reply #22 on: January 29, 2011, 04:35:58 AM »

Oh, just to keep you confused, Eagles that use dropboxes are also angled this way.

NO, Eagle offset the engine to the driver's side so the shaft is stright into the dropbox.
Jack
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« Reply #23 on: January 29, 2011, 05:28:56 AM »

I really like that engine cradle. Do you have drawings for it. I would love to build on for 8 with an 8V-71.
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bevans6
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« Reply #24 on: January 29, 2011, 06:32:45 AM »

I built it based on the dimensions published in the MC9 manual.  The big modification was using the four posts instead of a big sheet metal box.  It just picks up the engine on the oil pan flange.  Couple of points - the manual calls for 12" wide at the pan flange pickup points, 11 5/8" or 11 3/4" would  be better, the pickup points are just a tad too wide.  Also make sure you get it as far back as possible, the tranny weighs a lot and the balance point is not far forward of the rear of the block where the rear pickup points are.  The main beams are 4" square 3/16" wall cold rolled mild steel, the uprights are 2" by 4" 3/16" wall CRMS, the casters are 1,000 lb nylon tired, steerable.  Since the engine is installed at an angle on the MC-5 all four need to steer, since the dolly actually rolls back at an angle  as it comes out of the bay.  And once you have it in your shop, you can spin the engine around in place to make it easier to get at.

I just bought all the steel cut to size, except for the bevels on the up rights, and welded it together one Saturday.  It took longer to paint than it did to build, but I wanted it to look pretty 'cause I planned to post pictures of it!  it's bloody heavy, though.

Brian
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« Reply #25 on: January 29, 2011, 10:30:38 AM »


Where's the gun?   Grin Grin ;

  LOL. I get it now, thanks for your patience.

  Brian, thank you for those pics, they help a great deal in understanding how its put together. May I assume the engine cradle "slides" into the bus on some ledge along the chassis? Do you just lose some air to drop the bus away from the cradle and roll it out??

  Your trailer hitch, is it attached to the engine cradle, or the Bus chassis? Whats the best way to attach???

  How long does it take to pull the motor out??
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buswarrior
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« Reply #26 on: January 29, 2011, 01:39:42 PM »

Two old wrenches that I know, deep into retirement now, in their youth and enthusiasm, while working for the old fleet, unionized shop, decided to see how fast they could get one out. Removing the drive train was a routine for them, as they did it regularly...

Coach positioned on the hoist, clock started with opening the engine doors, clock stopped when the drive train was hauled clear on the dolly.

45 minutes.

And they never did it again after the careless comments made by the shop foreman regarding a permanent change of pace...

happy coaching!
buswarrior

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« Reply #27 on: January 29, 2011, 01:57:40 PM »



And they never did it again after the careless comments made by the shop foreman regarding a permanent change of pace...

happy coaching!
buswarrior



  Well, thats unions for ya. Anything that can me done in an hour, make it four.   
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bevans6
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« Reply #28 on: January 29, 2011, 02:13:41 PM »

If you look at picture 1010304, up there, there is a triangular plate with a tube in the middle at the bottom of the engine bay.  that is the rearmost part of the engine frame.  that is where the hitch bolts to, along with a stretcher that goes across the bay from side to side.  the bumper bolts on over the whole thing.  those triangles are fully integrated into the whole rear frame structure, transfer loads back up to the floor and the roof, and are extremely well supported.

It took me, working completely alone, about three honest days to pull the engine.  That included the blocking and jacking and all of that, four hours to disconnect the drive shaft (never under estimate the power of a rusty bolt to not undo in a very hard to reach spot), taking a lot of notes and labeling so that I had a hope of putting it back together, and never having done it before.  There is a ton of plumbing and joints to disconnect, clutch and shift linkage, and if you haven't done it before you don't know the best way to do it.  There is not a lot of clearance above the engine on the  MC-5.  As an example, when you drop the bus down to put the engine on the dolly to roll it out, you have 1/2" to work with.  I had to remove the governor from the air compressor because it will not clear when you drop down the bus...  You have to figure out a place to put 20  gallons of coolant so that it doesn't run down into your neighbours horse paddock, on and on and on.  FWIW we once pulled an engine out of an original Mini in 20 minutes, so I know how to work fast with experienced partners...

Brian

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1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
Spicer 8844 4 speed Zen meditation device
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1972 NTM MK-4 B/SR
RJ
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« Reply #29 on: January 29, 2011, 04:09:44 PM »

Paul -

How long does it take to pull the motor out??

I had a tour of the San Francisco Maintenance Shop for Greyhound back in the early '70s.  At the time, they were running mostly GMs, but the MCIs were beginning to infiltrate.  This was a full-service shop - they did complete engine, transmission and rear axle overhauls, as well as brakes, upholstery, body shop, etc.  The overhaul shop always had several complete powerpacks (engine/transmission) sitting on pallets ready to go on a daily basis.

Just to show you the difference, two journeymen mechanics working together could R & R a complete powerpack on a V-drive GMC before noon, then do a second one after lunch.  That's right, two buses a day in and out of the shop.

It would take those same two fellows all day to do a powerpack R & R on a T-drive Scenicruiser or any of the MCIs.  One bus per day vs two.  (Can you guess which coach manufacturer had the better design from a service standpoint?)

Sadly, that shop is now closed, all they do is minor repairs (restroom service, sweep/mop, wash rack, brake adjustments and light replacements).  The only HD shop that I know of on the West Coast for Greyhound now is in Los Angeles (where the historic fleet is stored, btw).  Seattle or Portland might have one, but I'm not sure.

All this was back in the days before the Hot Dog Salesman took over the company.

FWIW & HTH. . .

 Wink

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RJ Long
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« Reply #30 on: January 29, 2011, 08:09:52 PM »

RJ, there has been zero maintenance in Portland for years.  I heard they outsourced maintenance in Seattle recently or moved to the Gray Line Seattle shop on West Marginal Way, but don't know for sure.  The old Portland shop has been sitting empty and falling down for many years.  Both locations use Pacific Power (formerly Pacific Detroit Diesel Allison) for heavy maintenance when necessary.  I saw a pic of the old Portland shop on some site a while back, but in any event it is waiting to be torn down by the city.  You can see it right below the Marquam bridge (I-5) where I-405 splits off.
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« Reply #31 on: January 31, 2011, 03:51:16 AM »

  Would the drop box attach to/work on a two speed rear axle? I do realise the drive shaft would probabnly need to be lengthened, just curious if its possible. 
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« Reply #32 on: January 31, 2011, 08:28:28 PM »

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« Reply #33 on: February 01, 2011, 04:28:31 AM »

There is no way to put in a two speed rear with the drop box.
Now someone will find a way.
Jack
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« Reply #34 on: February 01, 2011, 04:54:08 AM »

Hmmm, lets see,.....if you flipped the rear end and turned the dropbox on its side and added a........ Grin
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