2012 slows down fast for an automatic
JK Enthusiast
Joined: May 2011
Posts: 482
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From: heart of dixie
This has been covered in other threads. The Hill Start Assist (HSA) contributes to quick coast down.
A few of us tested this and posted back a couple months ago. I appears the HSA system starts applying some brake when you lift off the gas. It is more noticable on hills. When HSA is turned off, the quick slow-down goes away. I keep HSA turned off all the time. Its a mall-crawler feature for people who can't drive anyway.
Not to say there isn't something else contributing to slow-down on the 2012, but HSA is part of the picture.
Turning off HSA is covered in the manual.
Search up "HSA" on the forum and there will be lots of posts.
A few of us tested this and posted back a couple months ago. I appears the HSA system starts applying some brake when you lift off the gas. It is more noticable on hills. When HSA is turned off, the quick slow-down goes away. I keep HSA turned off all the time. Its a mall-crawler feature for people who can't drive anyway.
Not to say there isn't something else contributing to slow-down on the 2012, but HSA is part of the picture.
Turning off HSA is covered in the manual.
Search up "HSA" on the forum and there will be lots of posts.
JK Super Freak
Joined: Mar 2011
Posts: 1,934
Likes: 2
From: Seattle, WA
Originally Posted by jhol111964
That makes sense. I experimented with coasting and thottling yesterday, and there's something definitely dragging when releasing the accelerator at speed. Dragging = bad, imo. I was able to moderate it with partial throttle to use a little bit of engine braking properly and appropriately, so its manageable. But it remains to be seen if its costing me extra fuel, as I use partial throttle/fuel to offet the drag from the HSA or other "smart" feature.
I can see this being helpful if we are stepping on the brake and the Jeep makes the engine help stopping, as we do with a manual transmission. Same if we have cruise control on and start going downhill the Jeep uses the engine to help controlling speed. Nothing difficult to implement via software.
JK Enthusiast
Joined: Dec 2006
Posts: 297
Likes: 0
From: West Los Angeles
My 2011 Rubi Unlimited auto trans seems to really slow down more than any other vehicle I've owned when you let off the gas, so maybe it has this feature? I'm talking about street and highway driving. It's the only vehicle I've ever owned that will almost just sits there on level ground if its running and in gear and your foot is off the brake. Every other vehicle I've owned would move forward in gear and foot off the brake. I've thought that maybe its sort of a helpful off-road feature too? So you could drive slowly through rough areas and not have the Jeep be pushing you too fast?
Thread Starter
JK Enthusiast
Joined: Feb 2009
Posts: 335
Likes: 1
From: Keller, Tx
My 2011 Rubi Unlimited auto trans seems to really slow down more than any other vehicle I've owned when you let off the gas, so maybe it has this feature? I'm talking about street and highway driving. It's the only vehicle I've ever owned that will almost just sits there on level ground if its running and in gear and your foot is off the brake. Every other vehicle I've owned would move forward in gear and foot off the brake. I've thought that maybe its sort of a helpful off-road feature too? So you could drive slowly through rough areas and not have the Jeep be pushing you too fast?
eta: my kids 11 is nowhere near as bad as my 12 (his feels like a caddy compared to mine).
JK Freak
Joined: Feb 2009
Posts: 580
Likes: 1
From: Allentown, NJ
Originally Posted by f2fast4u
Define late build 3.8L - because I had a mid-year 2011 Rubicon that didn't do that.
Curious because everything else I've heard/read is that it's transmisson specific (the non-coasting and slap stick features). Shutting off the fuel and changing the torque convertor/tranny workings are two separate worlds.
Actually, if you wanted to squeeze extra mileage out of the JK you'd shut off the fuel and let it coast at the same time, not brake it.
JK Newbie
Joined: Sep 2011
Posts: 36
Likes: 0
From: Louisiana
My 2012 does it but I always attributed it to the transmission down shifting. If you watch the tachometer you'll normally catch about a 200 rpm increase when it happens. A lot of automatics will wait to down shift when you get back on the gas after coasting. The Jeep seems to down shift as you slow.
JK Newbie
Joined: Jul 2011
Posts: 24
Likes: 0
From: Central Kentucky
My '11 has slowed down quick from letting off the gas since day 1.
Coming from a diesel, I quickly attributed this to Jeeps use of locking the torque converter more often, to get fuel economy numbers up. These jeeps stay locked up a LOT more than they used to, and it causes that "sluggish" feel. But it's a good thing for multiple reasons.
Coming from a diesel, I quickly attributed this to Jeeps use of locking the torque converter more often, to get fuel economy numbers up. These jeeps stay locked up a LOT more than they used to, and it causes that "sluggish" feel. But it's a good thing for multiple reasons.
JK Enthusiast
Joined: May 2011
Posts: 160
Likes: 0
From: Dallas, Texas
I noticed this when I added my tires. My guess is no one here is running stock wheels. I had 16's and they rolled like crazy. Put on 33's and 17" rims and I thought my brakes were on. I even posted about it. It's the tires.
JK Super Freak
Joined: Jun 2008
Posts: 1,071
Likes: 1
From: Attleboro, MA
Sounds like Chrysler might have modified shift points and torque converter locking points. In a common 4 speed electronically controlled tranny, normally the TC only locks in 3rd or 4th gear, and only when above ~40mph. Like the poster above says, I wonder if they're locking it more often.
The TC should totally disengage on it's own when power is removed under its rated stall speed - approximately 2,000rpm or so.. that is, unless the TC lockup clutch is activated.
FWIW, my wifes later model 3-series beemer will engine brake itself down to about 15 mph. It's kinda fun.
The TC should totally disengage on it's own when power is removed under its rated stall speed - approximately 2,000rpm or so.. that is, unless the TC lockup clutch is activated.
FWIW, my wifes later model 3-series beemer will engine brake itself down to about 15 mph. It's kinda fun.
JK Enthusiast
Joined: Nov 2008
Posts: 237
Likes: 0
From: Stratford, WI
I have a 2011 Ram 1500 with a Hemi and a 5 speed auto and it acts the same as the 2012 JK. It is very noticable on the Ram when it is in Tow/Haul mode. I kind of like it, it's like a jake brake!
