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Author Topic: Third Gear Allison 740  (Read 773 times)
Miss Scarlett
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« on: July 23, 2013, 07:41:41 PM »

Do any of you guys with a 740 run third gear when doing hilly curvy 2 lane roads? I recently did a trip with a lot of 35 to 55 mph driving and the bus seemed happier and much more responsive in 3rd than in 4th. Is it ok to just put it in 3rd and run at those speeds?
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Miss Scarlett is an Eagle 10 with a 6v92 and Allison 740
UPDATE: finished enough to use!!!- exterior will remain original.
-Dan
Seayfam
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« Reply #1 on: July 23, 2013, 07:53:21 PM »

I do with mine. Anything under 50mph my tranny will hunt for gears, so I just put it in 3rd.
I try and always shift my tranny manually.
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Gary Seay (location Alaska)
1969 MCI MC-6 unit# 20006
8V92 turbo 740 auto
more pics and information here     "  www.my69mci-6.blogspot.com  "
luvrbus
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« Reply #2 on: July 23, 2013, 07:54:15 PM »

The 2 most common rear gear ratio for the Eagle are the 3:73 or 3:36 if you have the 3:36 third gear is wicked on a 740 and Detroit's love it with the 3:36 you can run up to around 62 to 65 mph depending on the rpm setting

 I loved my 3rd gear on the 740 with the 3:36
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Life is short drink the good wine first
Miss Scarlett
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« Reply #3 on: July 23, 2013, 08:19:33 PM »

Mine seems to hit the governor at about 55 in 3rd. I wish I could get it to downshift from 4th to 3rd at 55 on hills so I could keep my revs up. Even if I put it in 3rd and floor it, it will still wait until 46mph to downshift. However, driving in 3rd at the lower speeds eliminates that.
It runs much better with the new turbo. It climbed Rockwood Mountain on I-40 at 65mph in 4th and it would have never done that before.
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Miss Scarlett is an Eagle 10 with a 6v92 and Allison 740
UPDATE: finished enough to use!!!- exterior will remain original.
-Dan
luvrbus
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« Reply #4 on: July 23, 2013, 08:23:59 PM »

55 mph is about right for the 3:73 gears and the 740 in 3rd keep your eyes open for 3:36 rear gear you will love it
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Life is short drink the good wine first
lostagain
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« Reply #5 on: July 23, 2013, 08:52:39 PM »

I swapped my 4:11 for a 3:36 a couple years ago. I went from 2200 rpm to 1700 rpm at 65 mph. 3 rd gear (HT 740) takes me to 55 mph. 2nd gear to 40 mph. Greatest improvement I have done to my bus. The loss of power is more than compensated by the fact that you can downshift at a higher speed. So yea, running in 3 rd below 55 mph can be good if you need the power. Although with the 6V92TA, I have good torque down to 1500 rpm or so, so 4th gear is good too on flat terrain. 2 nd is great in the city, up to 40mph. Running higher rpms is fine, just might use a little more fuel. Running lower rpms at a higher gear is ok too, as long as you don't lug the engine. Watch the temperature too, lower rpm in high gear and stepping on it will warm it up fast. Drop down to 3 rd at 50, 55 mph and  your temp will go back down to 180F.

JC
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JC
Invermere, BC
1977 MC5C, 6V92/HT740
RJ
Former Giant Greenbrier Owner
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« Reply #6 on: July 23, 2013, 10:42:34 PM »

Dan -

You've got the right idea, but I think I may have an answer for you as to why you can't get the downshift done when you want it.

I found it worked best if you started about 3 mph over the max governed speed in the next lower gear.  The trick seemed to be to come OFF the throttle for just a second as you manually downshifted (taking the load off the driveline), then immediately coming back on the throttle.  With practice, you'll get the timing down, and your shifts will be smooth and right where you want them.

Give it a try, but it will take some practice.  For more details:

http://busnut.com/forum/index.php?action=articles;sa=view;article=41

FWIW & HTH. . .

 Wink
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RJ Long
PD4106-2784 No More
Fresno CA
luvrbus
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« Reply #7 on: July 24, 2013, 05:42:34 AM »

Buy you a 740 manual you can adjust a 740 to do about anything you wish through the valve body and governor,then they have a dozen different torque converters but that gets a little pricey when one goes there 

good luck
« Last Edit: July 24, 2013, 05:46:33 AM by luvrbus » Logged

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HB of CJ
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« Reply #8 on: July 24, 2013, 12:52:11 PM »

Only you do not have a clutch pedal.  The engine is much happier running at 1500-2100 without bouncing around as the Allision 740 "hunts" for the correct gear, plus you will get a little bit more engine braking when you need to slow down for those pesky curves.  With a Jake, the higher rpm really helps also.  Enjoy.  HB of CJ (old coot)
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Miss Scarlett
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« Reply #9 on: July 24, 2013, 07:07:49 PM »

Thanks guys, I will start practicing the downshift and get a manual. I always drove a stick with the old 6-71s and shifting or making it run the RPMs I wanted it to was never a problem. I suspect my tranny could use some adjusting so I will keep that in mind as I learn. In gears 1 and 2 it will upshift even if I don't which I really don't like going downhill. In 3rd it will stay and hit the governor at 55. In 4th I hit the governor at 74 MPH. I LOVE driving this bus! Camping trip to Lillydale coming up this weekend.
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Miss Scarlett is an Eagle 10 with a 6v92 and Allison 740
UPDATE: finished enough to use!!!- exterior will remain original.
-Dan
luvrbus
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« Reply #10 on: July 24, 2013, 07:32:44 PM »

The modulator controls the shift if you have the cable type they are pretty easy to adjust now the air modulator is a different story that adjustment is all done with the length of the hose it can be fun
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Life is short drink the good wine first
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