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  #13  
Old 08-19-2013, 04:26 PM
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Re: 8 Speed Transmission Downshifting Behavior

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Originally Posted by mswlogo View Post
I got an email on 7/19 it was "Scheduled" to go into production. So I should be ok.

Thanks.
Never hurts to double check... the only flash I've seen mention of is for the 8 speed in the V6, which isn't the same transmission as the V8.

You may be triggering the downhill mode. I've noticed that if I abruptly drop my foot from the gas, the transmission seems to stay in the same gear for a bit of engine braking. You could try turning it off to see if that changes behavior.
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Old 08-19-2013, 04:28 PM
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Re: 8 Speed Transmission Downshifting Behavior

Bring up your instantaneous mileage display.
When you drop the gas, the fuel to the engine is shut off, and mileage should go to "99" [suspect no room for three digits]
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Old 08-19-2013, 04:38 PM
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Re: 8 Speed Transmission Downshifting Behavior

the downhill mode is a button by itself. And only works in low range.
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Old 08-19-2013, 09:02 PM
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Re: 8 Speed Transmission Downshifting Behavior

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Originally Posted by mswlogo View Post
For those that do like to shift into neutral (usually sticks), the savings in free wheeling with engine idle is better than in gear, dragging down your coasting distance despite fuel is shut off or lean.
If fuel delivery is shut off or the engine enters a lean burning phase - it would surely burn less juice than at idle which is what a gear shift into Neutral achieves. But it can only make so much sense. You're not the only one driving manual transmissions around here. And some of us have more advanced electronics hooked up to their cars to lie to us than the wallet:

Boost = -7.25 psi
Air Fuel Ratio = 14.81 AFR
Knock = 0.00
Coolant Temperature = 85 deg C
Mass Air Flow = 23.58 g/s
Throttle Opening Angle = 12.76%


The AFR is one of the gauges I always look at since if I run lean under acceleration, I have to PARK the car immediately. When I lift from the gas, in gear, it goes to 20.00 which is the maximum readout from the stock Subaru sensor. At idle or in a steady state (like here on cruise control at 60 mph) it floats around 14.7 wheras under heavy acceleration it will go to 11.x
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  #17  
Old 08-19-2013, 09:31 PM
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Re: 8 Speed Transmission Downshifting Behavior

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Originally Posted by hemi15 View Post
There are lots of things some are small some are very unlikely but it sure does increase the risk. Not so much for cars but much more for heavy commercial vehicles. Many high grade downhills has a sign stating that you should cruise down at gear.

1- your brakes could get hot and extend stopping distance after a high grade long downhill. (Semi`s wont be able to stop.)
2- If a problem happens in the engine it can shut down in neutral and you wont have the power steering and brakes in that condition. In gear this will never happen. (sticks can put into gear, release clutch and can survive in this case but autos can not.) Put it in N turn off the car at a small incline and try to steer and brake. You will never put in N again while cruising.
3- In case you need to accelerate you wont be able to do it quick enough.

I don`t believe cruising in N will help you to save gas actually you will consume more since you have to burn gas to keep engine running at idle and idling is not the most efficient way of running an engine.
Those are pretty weak safety arguments. I thought you'd come up with something better.

The increase in coasting (out of gear) is more gain than the cost to idle engine on most cars. People do this ALL the time with sticks. Google Hypermiling it's a very natural thing to do with a stick. If I want to slow down then I put it gear.

Watch the computer readout. If you put in Neutral it will usually go off scale (above 99 MPG). If you leave it in gear, it will be high but not nearly as high as in Neutral. I have not tried this with Jeep.
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Old 08-19-2013, 09:40 PM
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Re: 8 Speed Transmission Downshifting Behavior

Coasting in Neutral or Gear to Save Gas - Coasting and Fuel Economy - Popular Mechanics

http://www.caranddriver.com/features...neutral-page-3
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  #19  
Old 08-19-2013, 11:39 PM
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Re: 8 Speed Transmission Downshifting Behavior

I'm glad the Jeep downshifts to use engine braking. One of the reasons I prefer standard transmissions is for the increased control, and this feature takes a step towards bridging that gap.

If you don't want the engine braking, just give it a very small amount of throttle, or use the paddle shifters. This makes perfect sense to me, you have the best of both worlds.
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Old 08-20-2013, 12:18 AM
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I have two Fords fitted with the 6 speed ZF transmissions
Generally the car will coast on down hill gradients.
If however you have the cruise control set, and on a downhill gradient, the transmission will drop back through the gears to provide ample engine breaking to maintain the set cruise control speed
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Old 08-20-2013, 04:07 PM
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Re: 8 Speed Transmission Downshifting Behavior

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Originally Posted by mswlogo View Post
My wallet says different on the MPG. Google it.

But I am curious about the safety. If your staying within reasonable speeds and possibly use up break pads a little faster.

Why is it unsafe?

I'm not suggesting to do it, in the Jeep. But folks with sticks do it all the time and I continue to do.
I wouldn't argue that it is unsafe, with modern brakes.
However, in some states using hillbilly overdrive isn't legal--cause the laws tend not to be updated since the 40s and 50s when brakes would burn out on long grades.
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Old 08-21-2013, 06:49 AM
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Re: 8 Speed Transmission Downshifting Behavior

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Originally Posted by lstowell View Post
Never hurts to double check... the only flash I've seen mention of is for the 8 speed in the V6, which isn't the same transmission as the V8.

You may be triggering the downhill mode. I've noticed that if I abruptly drop my foot from the gas, the transmission seems to stay in the same gear for a bit of engine braking. You could try turning it off to see if that changes behavior.
How do I turn that off. Thats exactly what it's doing.
It kicked down and I let off quickly and it stayed down.
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