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Author Topic: GEAR RATIO, REAR END ?  (Read 6353 times)
Just Dallas
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« Reply #30 on: February 18, 2010, 03:44:03 PM »

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« Last Edit: July 15, 2010, 11:24:57 AM by Now Just Dallas » Logged

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« Reply #31 on: February 18, 2010, 04:51:40 PM »

Jim,

Whichever way it is if it is done wrong it will be pretty obvious!!

I'm pretty sure it is rev/2 because I remember being surprised at how fast that drive shaft turned when I turned the wheel.
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Ed Hackenbruch
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« Reply #32 on: February 18, 2010, 05:47:51 PM »

Brian, i am not saying that you are wrong or made a mistake.  Algebra is not my strong suit so no formulas from me. Smiley  All i am saying is what i have experienced. Now if it was just me, i would be wondering if i just imagined it, but i am not that senile......yet! Grin  And since two other people with 5's have also done it and one has proof in the form of a ticket, you can see why i have to question a statement that says that X mph is all that is possible and you can not go faster than that.  Bus races!!!!! we need to find a big long track somewhere that we can test buses on! Grin
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1968 MCI 5A with 8V71 and Allison MT644 transmission.  Western USA
NewbeeMC9
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« Reply #33 on: February 18, 2010, 06:12:26 PM »



What is the gear ratio of the drop box Huh    them number must be included in the numbers game Grin
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hargreaves
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« Reply #34 on: February 18, 2010, 07:30:15 PM »

Just to chirp in, if my bus could do 100 mph I would gladly take the ticket and frame it and put it on the wall for everyone to see. LOL
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now as of Feb 2012 series 50 B400  . Sunshine Coast British Columbia
bevans6
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« Reply #35 on: February 19, 2010, 05:23:04 AM »

drop box ratio on an MC-5 is 1:1.

You can bring a horse to the water, but you can't make him drink...
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1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
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TomC
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« Reply #36 on: February 21, 2010, 08:34:50 AM »

It is really hard to determine tire rotation per mile just by measuring or using measurements from the manufacturer.  Different tires have different deflections.  A 11R-22.5 can have RPM's (revs per mile) of 497 to 505.  The best is to get the exact tire and go to your tire manufacturer to get the rpms of that tire.  For example- a tire my seem to get 1850rpm at 62mph with 3.33, but using the 500rpm (which is most common), the actual engine speed at 62mph is 1720rpm-a difference of 130rpm!  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #37 on: February 24, 2010, 02:17:58 PM »

I thought I would chime in...

i have the Mc5 with the 8v71 and the alison 644. 12r22.5 tires. I am not sure what my ratio is. I just got back from a 48 hour trip and my top speed is about 75mph at 2400rpm (I must have the 3.71 gears?)

rpm guage a little bouncy
Speed on guage not gps.




my old mc5 with the spicer and no rpm guage would run in excess of 80mph - I never did find the top speed but there was lots of peddle left Smiley
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« Reply #38 on: February 24, 2010, 02:43:44 PM »

75mph @ 2,400rpm with 12r-22.5 tires (486rpm) makes for a 3.95 ratio.  So either your speedo is off or your tach is off.  But your close enough to say you have the 3.73 ratio.  Good Luck, Tomc
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
Ed Hackenbruch
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« Reply #39 on: April 11, 2010, 04:40:22 PM »

Just a quick update on this.  A couple of days ago we were on I-40 headed east out of Flagstaff. The speed limit is 75.  As is the case almost everywhere people were going a lot faster. Smiley  I got out the gps and checked my speed. I knew my speedo runs 3-4 mph fast as verified by, 1. my wife clocking me in our car. 2. going past many roadside radar units that are there to let you know your speed when entering a construction zone. 3. Freeway mileage test areas. And 4. By my gps.  All say the same, actually the gps was the most precise, it said my speedo was reading 3.8 mph fast.  Sooooooo, i  ran the bus up until i hit 80.1 mph. I was in 4th gear with my MT 644 and i was turning 1900 -1950 rpm. Still had throttle to spare. Sorry Brian, but i didn't want to get a ticket so i did not try to find out what my top speed is. Plus we were towing our jeep too. Grin
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1968 MCI 5A with 8V71 and Allison MT644 transmission.  Western USA
luvrbus
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« Reply #40 on: April 11, 2010, 04:48:36 PM »

Ed, do you want to sell your drop box I'll even do the change out I believe you one of the rare .93 ratios from Rockwell


good luck
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DaveG
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« Reply #41 on: April 11, 2010, 04:51:55 PM »

Okay Brian, do the math again using the .93 and see how it turns out.......
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Tom Y
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« Reply #42 on: April 11, 2010, 05:39:48 PM »

Clifford, What did the .93 ratio units go in?  Thanks Tom
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Tom Yaegle
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« Reply #43 on: April 11, 2010, 08:33:53 PM »

Tom Y they were used in the Rolligons high flotation trucks back in the 60's and 70's before they went to the hydraulic drive.
They had a gear and yoke at the bottom where normanly it would bolt to 3rd member where the pinion gear was you just removed the bottom cover ,gear and the yoke and they would bolt up to differential on a Eagle or MCI 5.
It is a hard item to find but they are out there I found 2 in New Iberia La but the bull gears were missing and you can not buy that gear off the self now it has to be cut on special order for 4 grand .   



good luck
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Tom Y
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« Reply #44 on: April 12, 2010, 04:47:33 AM »

Luvrbus, Thanks for the info.  Tom
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Tom Yaegle
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