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Old 10-13-2017, 07:00 AM   #1
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Upshift/downshift/up/down/up/down

While climbimg pretty hard the trans cycles up and down about 3 seconds per cycle. I usually let up on the gas to stop it or we reach the top.its like it can't decide 5th 4th.....
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Old 10-13-2017, 08:02 AM   #2
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Upshift/downshift/up/down/up/down

When climbing, watch your RPM and try to keep it at 1500-2000. Do this by manually downshifting. Not sure of your tranny, but 5th & 6th is typically considered overdrive. This keeps engine from bogging down too much, keeps it running smoother, and keeps engine & tranny running cooler. The “Big Mike” magic uphill RPM # is 1900. Lastly, if you’re going downhill right after climbing (think mtns), use the same gear going down that you used going up. Engine brake will help you out a lot in that case. Hope this helps.
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Old 10-13-2017, 08:19 AM   #3
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You have to shift an automatic? I didn't know that.
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Old 10-13-2017, 08:31 AM   #4
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You have to shift an automatic? I didn't know that.
You don't have to, but you can
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Old 10-13-2017, 02:01 PM   #5
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While climbimg pretty hard the trans cycles up and down about 3 seconds per cycle. I usually let up on the gas to stop it or we reach the top.its like it can't decide 5th 4th.....
Sounds like this is a situation where you're trying to climb a hill that takes more engine horsepower to pull than can reach the ground in top gear.

As you climb the hill, the vehicle slows and the transmission downshifts to compensate because the vehicle is slowing down. That gets more power to the wheels because of the change in engine RPM and transmission gear ratio. The vehicle speeds up and the transmission upshifts. The vehicle slows because of the hill, and the cycle starts all over.

You gotta remember driving a large motorhome isn't like driving a car. A car has a very high power to weight ratio. You can put most cars in drive and pull any hill on the interstate without the transmission downshifting. A motorhome is more like a big truck. Its powertrain is spec'd to get this great big load down the road.

You could probably pull that hill and stay in top gear with:
1. More horsepower or
2. A deeper rear axle which would limit your top speed or
3. When it starts to cycle, preselect down one gear to top the hill without the cycling.
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Old 10-13-2017, 02:09 PM   #6
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Ok, thanks. today when it did it, the tach was at 2200. I didn't think o should downshift
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Old 10-13-2017, 02:27 PM   #7
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Sounds like you’re getting a handle on it.
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Old 10-13-2017, 04:09 PM   #8
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While on the subject, if you do manually select a lower gear will it hold that gear or downshift again if needed. I have a six speed
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Old 10-13-2017, 04:20 PM   #9
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Ok, thanks. today when it did it, the tach was at 2200. I didn't think o should downshift
Is this vehicle equipped with a gasoline engine or a diesel?
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Old 10-13-2017, 04:25 PM   #10
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While on the subject, if you do manually select a lower gear will it hold that gear or downshift again if needed. I have a six speed
For example, if you manually select a six speed transmission down to five, the 6-5 downshift will be on what is called the preselect downshift schedule It's a higher RPM than the automatic, closed or wide open throttle downshift.

If you are in 5th and forget to go back to drive, and start accelerating down a hill, it will eventually automatically upshift to sixth at a high engine RPM. The idea here is to try to prevent the engine from a catastrophic failure. That's something I don't recommend testing.

If you are manually selected into 5th, the 5-4, 4-3, 3-2 and 2-1 downshifts will occur at their normal speeds.
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Old 10-13-2017, 05:53 PM   #11
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Thank you dbarton
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Old 10-13-2017, 06:21 PM   #12
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While climbimg pretty hard the trans cycles up and down about 3 seconds per cycle. I usually let up on the gas to stop it or we reach the top.its like it can't decide 5th 4th.....
I never manual shift the Allison 6 speed transmission in the last 16 years. I set the cruise control and let her roll. If yours is constantly upshifting or downshifting every 3 seconds on every hill, then Allison probably needs to have a look at the computer programing. Sounds like something is not set right. Maybe the previous owner made some changes for some reason?
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Old 10-13-2017, 06:29 PM   #13
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It's also possible the engine is down on power and the transmission is responding. Shift cycling on a hill is usually because the vehicle doesn't have enough power to make the hill.
I suppose it's possible somebody jacked around with the transmission programming, but I'd start with the engine power if a problem is suspected.
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Old 10-13-2017, 08:59 PM   #14
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I agree with Les
When I am starting into a grade and the RPM starts to drop slowly, I manually downshift, bringing the RPM up to the 2300 -2400 range rather than allow it to drop down and automatically downshift.

Like said above, this brings RPM up, keeping the radiator and motor running cooler, and keeps from lugging the diesel motor. On some long pulls my rig could shift in and out of OD 4-5-or 6 times if left in overdrive. This cannot be good for the trans.

YES, you can leave it in OD, and yes, some rigs have a big enough motor to handle it, but if you are marginal on the HP ratings like I am (330HP in a 40' Newmar) it just works better to do it manually.

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