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-   -   Deceleration shudder on V8 (http://www.jeepgarage.org/f107/deceleration-shudder-on-v8-20506.html)

mjw930 03-19-2011 09:57 PM

Deceleration shudder on V8
 
As my truck gets broken in I'm noticing a deceleration shudder (or stutter to differentiate it from the other complaints). It's exactly as described in 21-004-10 but it's for the V6 and for vehicles built before July 26th???? I have a V8 built in January! Acceleration is fine, smooth as can be.

Quote:

SYMPTOM/CONDITION:
Some customers may notice that they feel a shudder during the following conditions:
For vehicles equipped with a 5.7L engine during acceleration between 40 - 60 mph
in Auto and Sport modes.
For vehicles equipped with a 3.6L engine during coast or deceleration from 60 mph
in Auto and Sport modes.

The DTCM software was configured to reduce the 4WD torque to the front axle during
non-slip events under normal driving conditions.
Has anyone else felt this?


Seems I put this is the wrong forum, can a Mod move this to the drive train section please? Thanks.

Nouveau Redneck 03-20-2011 10:29 AM

Re: Deceleration shudder on V8
 
I wouldn't call mine a shudder, but when I lift my foot a little to coast down a hill, trying to save a little gas, it feels like the brakes are being applied, and my Overland Hemi slows down. Any other automatic transmission that I have ever driven in my life, in the same situation, would coast along at least at the same speed as when I lifted my foot, and most would even increase in speed a little. I feel that I'm being cheated out of gas mileage because I have to keep my foot pressed down on the gas pedal to the point that the ECO light does not even light up in certain situations. I am maintaning speed down a hill and it doesn't allow me to lift my foot off of the pedal enough for the ECO light to come on. It only does it some of the time, and I haven't paid enough attention to it to be able to know the exact conditions that will reproduce it, but it's upsetting and I'm going to talk to the service department once I've collected more data.

mjw930 03-20-2011 02:17 PM

Re: Deceleration shudder on V8
 
Sean,

Yes, I think we are talking about the same thing. It's as if the torque converter is staying partially locked to provide engine braking. I don't know if it's a bad thing or simply something I need to get used to. it also seems to be more noticeable once everything is warmed up. I'm going to take it into the dealer for the radio update (assuming there really is one) and ask them to reflash the engine and trans modules even if the system says it's not needed. I had that issue with the ECM freezing where I had to remove the negative lead from the battery to get it back and I'm wondering if the ECM isn't properly initialized (note the TSB for the V6 explicitly states to reboot the ECM after the upload so it loads the new firmware into memory).

It will be interesting to see if anyone else comments (or whether they'll hate me for pointing out something they never noticed ;) )

litespeedz 03-20-2011 03:21 PM

Re: Deceleration shudder on V8
 
I noticed it too. There is a kind of front-back-front shaking motion that occurs when you take your foot off the gas at 40mph. Sometimes it is followed-up with a clunk. It's annoying and a little scary feeling. I think resetting the ETC helped the last time I tried it. I did it by putting the car in Run mode but with the engine off. I push the accelerator the floor slowly and release slowly two times. Turn it off. Start the car and drive. It seemed to smooth out the throttle responses, including taking your foot off the gas.

Right now, I am trying to get them to fix the WOT Shudder and my stupid rear flipper window. Those parts are on national backorder. I'm calling Jeep tomorrow to put some pressure on them. Maybe at some point I'll ask about this. One step at a time...

GlowingGhoul 03-21-2011 08:58 PM

Re: Deceleration shudder on V8
 
I have the same slight shudder...clunk on deceleration on my 02 GC.

Almost the same transmission and torque converter as the 2011 sorry to say. 9 years and they can't smooth out the driveline.

PS: That said, 545RFE's transmissions are supposed to be extremely reliable. I've heard a few transmission guys say they've NEVER seen one have a mechanical failure.

mjw930 03-22-2011 07:34 AM

Re: Deceleration shudder on V8
 
Quote:

Originally Posted by GlowingGhoul (Post 380182)
I have the same slight shudder...clunk on deceleration on my 02 GC.

Almost the same transmission and torque converter as the 2011 sorry to say. 9 years and they can't smooth out the driveline.

PS: That said, 545RFE's transmissions are supposed to be extremely reliable. I've heard a few transmission guys say they've NEVER seen one have a mechanical failure.

That's not the answer I wanted to hear but it's the one I expected :cool:

It's not bad and actually you become used to it, my Trailblazer and Touareg had similar "quirks". The Touareg would make all kinds of driveline noise under hard braking......

Nouveau Redneck 03-22-2011 09:53 AM

Re: Deceleration shudder on V8
 
I'm just pissed that it's making me press on the gas to maintain speed when I should be able to let it coast down a hill. With the price of 89 octane these days I want all the fuel economy I can get when I decide to get it.

litespeedz 03-22-2011 05:05 PM

Re: Deceleration shudder on V8
 
Quote:

Originally Posted by Nouveau Redneck (Post 380470)
I'm just pissed that it's making me press on the gas to maintain speed when I should be able to let it coast down a hill. With the price of 89 octane these days I want all the fuel economy I can get when I decide to get it.

There were two threads on this topic. I think it has to do with fuel being shut-off during coasting and using the wheels to move the cylinders. You are actually saving fuel it just feels different than we are all used to.

http://jeepgarage.org/showthread.php...ighlight=coast

http://www.jeepgarage.org/showthread...oasting&page=2

litespeedz 03-22-2011 05:07 PM

Re: Deceleration shudder on V8
 
Quote:

Originally Posted by GlowingGhoul (Post 380182)
I have the same slight shudder...clunk on deceleration on my 02 GC.

Almost the same transmission and torque converter as the 2011 sorry to say. 9 years and they can't smooth out the driveline.

PS: That said, 545RFE's transmissions are supposed to be extremely reliable. I've heard a few transmission guys say they've NEVER seen one have a mechanical failure.

It feels like this could easily be polished with some programing.

I do get the sense that this engine and transmission is near bulletproof. I just wish they had refined it a little more. Hopefully a TSB will be issued for it soon!

wk2silverbullet 03-22-2011 07:32 PM

Re: Deceleration shudder on V8
 
Just press the Tow/haul Button if you have it.

It gets rid of all the non-sense. For best result dial to Sport Mode.
try it see how it goes.

litespeedz 03-22-2011 07:43 PM

Re: Deceleration shudder on V8
 
I agree. A lot of this is better in Sport Mode...

mjw930 03-23-2011 09:11 AM

Re: Deceleration shudder on V8
 
I see a lot of comments on sport mode changing the performance profile but as I understand everything I've read the only things changed by sport mode are ride height, ESC (traction control) reduced and torque split biased towards the rear wheels. There's no mention of a change to the throttle response or shift patterns.

I believe the major reason it reduces (certainly doesn't eliminate it) the sensation is because of the rear biased torque split. Tow/Haul mode changes the behavior too but again, it's not eliminated.

It's something I would think they could eliminate through programming and if you believe all the hype about the millions of miles of continuous testing it's something that should have been noticed and addressed. Maybe, since it hasn't, that's an indication that they have done all hey can with the software and it's an artifact of the design? Who really knows??????

I'm not saying I'm dissatisfied with the truck, it's a great vehicle. It's just these little quirks that make it less than it could be and takes a bit of the shine off the new car luster.


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