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-   -   8 Speed Transmission Downshifting Behavior (http://www.jeepgarage.org/f73/8-speed-transmission-downshifting-behavior-64326.html)

mswlogo 08-19-2013 10:17 AM

8 Speed Transmission Downshifting Behavior
 
I have a Limited 2014.

I really have no complaints about the 8 Speed Transmission and saw lots of threads of abrupt shifting etc.

Mine was built 3 weeks ago so I'm pretty sure it has the latest firmware.

Anyway it may be behaving complete normal and just a matter of getting used to it. But I'm curious.

I was approaching a Green light when it turned Yellow and so I goosed it to get through the light. It downshifted perfectly.

But when I let up on the gas to coast through it stayed downshifted.

I brought the gas up normal and then it was fine.

It's like it switched to a "Sport Mode".

I really like how this Jeep coasts, so many automatics bring the revs up on the engine going down hill and seem to use more gas even if your foot is off the gas pedal.

One time going down a rural hill it seem to downshift and want to stay there. I was not sure if the this is the Hill Decent feature kicking in or what (I have it in Auto).

Roadmaster45 08-19-2013 11:40 AM

Re: 8 Speed Transmission Downshifting Behavior
 
Quote:

Originally Posted by mswlogo (Post 878739)
I have a Limited 2014.

I really have no complaints about the 8 Speed Transmission and saw lots of threads of abrupt shifting etc.

Mine was built 3 weeks ago so I'm pretty sure it has the latest firmware.

Anyway it may be behaving complete normal and just a matter of getting used to it. But I'm curious.

I was approaching a Green light when it turned Yellow and so I goosed it to get through the light. It downshifted perfectly.

But when I let up on the gas to coast through it stayed downshifted.

I brought the gas up normal and then it was fine.

It's like it switched to a "Sport Mode".

I really like how this Jeep coasts, so many automatics bring the revs up on the engine going down hill and seem to use more gas even if your foot is off the gas pedal.

One time going down a rural hill it seem to downshift and want to stay there. I was not sure if the this is the Hill Decent feature kicking in or what (I have it in Auto).

Check your build date if it was built before 7/14 then go to service and get the transmission flash done

bill_de 08-19-2013 11:40 AM

Re: 8 Speed Transmission Downshifting Behavior
 
Quote:

Originally Posted by mswlogo (Post 878739)
I have a Limited 2014.

I really have no complaints about the 8 Speed Transmission and saw lots of threads of abrupt shifting etc.

Mine was built 3 weeks ago so I'm pretty sure it has the latest firmware.

Anyway it may be behaving complete normal and just a matter of getting used to it. But I'm curious.

I was approaching a Green light when it turned Yellow and so I goosed it to get through the light. It downshifted perfectly.

But when I let up on the gas to coast through it stayed downshifted.

I brought the gas up normal and then it was fine.

It's like it switched to a "Sport Mode".

I really like how this Jeep coasts, so many automatics bring the revs up on the engine going down hill and seem to use more gas even if your foot is off the gas pedal.

One time going down a rural hill it seem to downshift and want to stay there. I was not sure if the this is the Hill Decent feature kicking in or what (I have it in Auto).

That's the car using the engine to assist in braking, as all vehicles should. I gives better control. Since the car is pushing the engine (not the other way around) you are not using any more gas.

mswlogo 08-19-2013 12:53 PM

Re: 8 Speed Transmission Downshifting Behavior
 
Quote:

Originally Posted by Roadmaster45 (Post 878784)
Check your build date if it was built before 7/14 then go to service and get the transmission flash done

I got an email on 7/19 it was "Scheduled" to go into production. So I should be ok.

Thanks.

mswlogo 08-19-2013 12:59 PM

Re: 8 Speed Transmission Downshifting Behavior
 
Quote:

Originally Posted by bill_de (Post 878785)
That's the car using the engine to assist in braking, as all vehicles should. I gives better control. Since the car is pushing the engine (not the other way around) you are not using any more gas.

You'd think so, but every Car I've had if I put it in Neutral on long down hills on the highway MPG goes WAY up. I always do this, if I'm driving a stick.

This car feels like it normally/frequently takes more advantage of down hills, that it feels like it free wheels and stays in 8th normally going down long hills on the highway. Which is great and I think partly why the MPG for this size truck is pretty damn good.

It's just in some instances (not on the highway), have not figured it out yet, it aggressively downshifts.

If it's in "Auto" does "Hill Decent" mode kick in on it's own sometimes?
Or does "Sport" mode also kick in on it's own (When in Auto). In other words, if I start driving aggressively will it downshift more aggressively on it's own when I let off the gas?

It does not feel wrong, it just feels different and a little unexpected.

f1anatic 08-19-2013 01:13 PM

Re: 8 Speed Transmission Downshifting Behavior
 
Quote:

Originally Posted by mswlogo (Post 878843)
You'd think so, but every Car I've had if I put it in Neutral on long down hills on the highway MPG goes WAY up. I always do this, if I'm driving a stick.

This car feels like it normally/frequently takes more advantage of down hills, that it feels like it free wheels and stays in 8th normally going down long hills on the highway. Which is great and I think partly why the MPG for this size truck is pretty damn good.

It's just in some instances (not on the highway), have not figured it out yet, it aggressively downshifts.

If it's in "Auto" does "Hill Decent" mode kick in on it's own sometimes?
Or does "Sport" mode also kick in on it's own (When in Auto). In other words, if I start driving aggressively will it downshift more aggressively on it's own when I let off the gas?

It does not feel wrong, it just feels different and a little unexpected.

it is both dangerous and will not save you fuel by placing the car in neutral when going downhill or coasting to a stop.

from the fuel efficiency standpoint, when the car is is neutral, the air fuel ratio will go back to stoichiometric 14.7 : 1 whereas when coasting in gear with foot off the gas, it will go to a lean burning 20-22 : 1. But don't take my word for it, research the matter yourself.

mswlogo 08-19-2013 01:29 PM

Re: 8 Speed Transmission Downshifting Behavior
 
Quote:

Originally Posted by f1anatic (Post 878852)
it is both dangerous and will not save you fuel by placing the car in neutral when going downhill or coasting to a stop.

from the fuel efficiency standpoint, when the car is is neutral, the air fuel ratio will go back to stoichiometric 14.7 : 1 whereas when coasting in gear with foot off the gas, it will go to a lean burning 20-22 : 1. But don't take my word for it, research the matter yourself.

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.

2014RedHemiGC 08-19-2013 01:42 PM

Re: 8 Speed Transmission Downshifting Behavior
 
Coasting in gear is a good thing. The computer goes into "extended coast down" mode shutting off the injectors using less fuel than idling in neutral.

mswlogo 08-19-2013 02:39 PM

Re: 8 Speed Transmission Downshifting Behavior
 
Quote:

Originally Posted by 2014RedHemiGC (Post 878869)
Coasting in gear is a good thing. The computer goes into "extended coast down" mode shutting off the injectors using less fuel than idling in neutral.

I'm not suggesting 2014 JGC does better in Neutral on MPG. I don't know and I would not shift Automatics into Neutral.

But I'm curious about the safety issue of free wheeling.

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.

hemi15 08-19-2013 02:44 PM

Re: 8 Speed Transmission Downshifting Behavior
 
Quote:

Originally Posted by mswlogo (Post 878861)
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.

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.

CNY_WK2 08-19-2013 02:57 PM

Re: 8 Speed Transmission Downshifting Behavior
 
Quote:

Originally Posted by hemi15 (Post 878895)
I don`t believe cruising in N will help you to save gas actually you will consume more since you have to burn oil to keep engine running at idle and idling is not the most efficient way of running an engine.

Why would you have to burn oil on idle? At idle, your injectors should be at essentially 0% injector duty cycle which has them pumping just enough gas to maintain the programmed idle.

I agree that idle is not the most efficient however they don't inherently burn oil unless you have some blow by your piston rings, etc.

hemi15 08-19-2013 03:06 PM

Re: 8 Speed Transmission Downshifting Behavior
 
Quote:

Originally Posted by CNY_WK2 (Post 878900)
Why would you have to burn oil on idle? At idle, your injectors should be at essentially 0% injector duty cycle which has them pumping just enough gas to maintain the programmed idle.

I agree that idle is not the most efficient however they don't inherently burn oil unless you have some blow by your piston rings, etc.

Sorry I wrote oil instead of gas by mistake.


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