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Old 01-15-2011, 08:09 AM
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Exclamation HEMI hestitated and "shook" during W.O.T.

I'm not sure yet if there is a need to worry or not--I'm hoping some discussion here will remedy that. I LOVE my overland, especially the V8. Yesterday, however (with 286 miles on it!), I am still breaking in the engine via the owner's manual and several recommendations here on this forum. For the first time twice while doing approximately 45mph, I'd open the throttle wide up and when I did, the HEMI for about 1-2 seconds did some shaking then it seemed to "kick in" and respond to my W.O.T. command. Out of the 4 times I did this yesterday, it did this twice! I definitely do not want to hurt or damage anything, but I don't want to be the guy who constantly calls or brings his new Jeep in for lack of knowledge or ignorance. I'll say again, I love this forum and respect the knowledge and appreciate the well of info you guys share so we can enjoy our vehicles!
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Old 01-15-2011, 08:17 AM
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Re: HEMI hestitated and "shook" during W.O.T.

sounds like you hit the rev limit, its a safty control that does not let the engine rev past a point that can hurt the motor, were you at a hight rpm? in auto stick mode(man shift)
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Old 01-15-2011, 08:33 AM
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Re: HEMI hestitated and "shook" during W.O.T.

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Originally Posted by ken07 View Post
sounds like you hit the rev limit, its a safty control that does not let the engine rev past a point that can hurt the motor, were you at a hight rpm? in auto stick mode(man shift)
I was at 45mph in Normal "Auto" (D) mode...it did this on the 2nd and 4th times out of the 4 times I did this yesterday. The RPMs never got close to redline (at least on the Tach). I know during breakin, they say no W.O.T. from standstill, rather from "at speed" like highway passing W.O.T. which I have been doing. Thanks for your help!
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Old 01-15-2011, 08:59 AM
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Re: HEMI hestitated and "shook" during W.O.T.

Probably the trans downshifting from 5th to 2nd Prime (there are 2 2nd gears). The engine is torque limited when the trans shifts to prevent damage. That's why it felt like it wasn't responding to your throttle input. At least that's my best Internet guess
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Old 01-15-2011, 09:42 AM
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Re: HEMI hestitated and "shook" during W.O.T.

Quote:
Originally Posted by THEPRFCT10 View Post
I'm not sure yet if there is a need to worry or not--I'm hoping some discussion here will remedy that. I LOVE my overland, especially the V8. Yesterday, however (with 286 miles on it!), I am still breaking in the engine via the owner's manual and several recommendations here on this forum. For the first time twice while doing approximately 45mph, I'd open the throttle wide up and when I did, the HEMI for about 1-2 seconds did some shaking then it seemed to "kick in" and respond to my W.O.T. command. Out of the 4 times I did this yesterday, it did this twice! I definitely do not want to hurt or damage anything, but I don't want to be the guy who constantly calls or brings his new Jeep in for lack of knowledge or ignorance. I'll say again, I love this forum and respect the knowledge and appreciate the well of info you guys share so we can enjoy our vehicles!
Same here! I don't know if the thread below pertains to us or not. Did Shudder TSB fix a problem? 2011 Shudder problems thread.
There is a TSB for WK2's built before July 26th, and a Star Case for WK2's built before Jan. 9th.
Possible issues: Bad Front Axle Isolator or maybe a bad Torque Converter. I thought I read the Torque Converter takes 6,000 miles to break in.
Pay attention to the posts from Milous. He is the man!

I did take mine to the dealer and even went for a drive with a tech. I'm pretty sure they think I'm crazy. I did show them the TSB and Star Case but they told me either one of those problems would occur all the time. I told them I didn't think they could reproduce what I'm feeling in a 10 minute drive.
Anyway, I do feel like mine has been better. I'm around 6,500 miles now so maybe my Torque Converter is broke in. I'm still thinking there is an issue and there will be another TSB in the future. I feel something at 30mph every now and then.

Did Shudder TSB fix a problem? 2011 Shudder problems thread


Quote:
Originally Posted by mjw930 View Post
Probably the trans downshifting from 5th to 2nd Prime (there are 2 2nd gears). The engine is torque limited when the trans shifts to prevent damage. That's why it felt like it wasn't responding to your throttle input. At least that's my best Internet guess
This sounds good to me too. However my '05 WK had a Hemi and Quadra Drive and it had 2 2nd gears and I never felt anything close to this... but of course this is a totally different monster.
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Old 01-15-2011, 10:21 AM
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Re: HEMI hestitated and "shook" during W.O.T.

My car does the EXACT same thing. I noticed it is when driving at 45mph and in Eco mode. If you punch it and let the car downshift the whole engine shakes. It doesn't sound like it, but it almost feels like the engine is missing. To me it feels like the Eco mode isn't dis-engaging. After 1 - 2 seconds it kicks in and goes.

I brought it in twice to have it looked at. In a roundabout way, they acknowledged it. They said that the transmission and torque converter have a 6,000 mile break-in period so there is little they can do. But then they told me that Chrysler engineers are always coming up with fixes so there could be a TSB for it at some point. I have approximatel 2,400 miles on my car and it still does it.
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Old 01-15-2011, 10:25 AM
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Re: HEMI hestitated and "shook" during W.O.T.

Quote:
Originally Posted by mjw930 View Post
Probably the trans downshifting from 5th to 2nd Prime (there are 2 2nd gears). The engine is torque limited when the trans shifts to prevent damage. That's why it felt like it wasn't responding to your throttle input. At least that's my best Internet guess
That's weird. My dealer told me there were two "4th gears" depending on if the torque converter was in lock-up mode or not. They said that is the reason for some of the vibrations at 45mph and cruising speeds. The torque converter is still "learning" when to lock-up and when not to.

I am also recalling that they told me the transmission learns and this was programming downshift issue. In other words, when you put your foot to the floor it is trying to learn what the optimal gear is. I was kind of surprised by that and didn't buy it. I agreed to keep an eye on it.

The weird part is the rest of the car drives great.
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Old 01-15-2011, 10:38 AM
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Re: HEMI hestitated and "shook" during W.O.T.

I can't really speak to any shake, and hope that it isn't the shudder from the drivetrain noted above. It doesn't sound like your engine is cold, but perhaps being new is enough to cause this and it could clear with a bit more break in and distribution of engine lube.

Note that you can and will experience a lag due to the Electronic Throttle Control (ETC), especially if you haven't been driving with a heavy foot. The ETC effectively "learns" your typical driving habits and if you're babying the rig then go to stomp on it, it may lag by a half tick or so. Many don't like this vs. a mechanically wired throttle from pedal, including yours truly.

Nate the Great's ETC reset method below:

Quote:
Originally Posted by White WK Swagga View Post
Here's the steps you need to follow:
1. Find an unused section of road with a good spot to pull-off/turn-around.
2. Pull off of the road and shut your car off.
3. Turn your key to the "On" position (but don't start the car), and wait for the 'idiot' lights to go out.
4. Press down on the accelerator, and let it back up.
5. Turn your car off.
6. Re-start your car and cruise up and down the road testing your throttle responsiveness.
Depending on how fast/slow you do the 4th step, your throttle will either become more or less sensitive/responsive.
Repeat steps #1 through #5 as needed until you're satisfied that your throttle response is as good as it's going to get.

Remember these things 'learn' how you drive so if you drive like Grandma for a few days, it's adjusts accordingly.
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Old 01-15-2011, 10:39 AM
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Re: HEMI hestitated and "shook" during W.O.T.

Quote:
Originally Posted by litespeedz View Post
That's weird. My dealer told me there were two "4th gears" depending on if the torque converter was in lock-up mode or not. They said that is the reason for some of the vibrations at 45mph and cruising speeds. The torque converter is still "learning" when to lock-up and when not to.

I am also recalling that they told me the transmission learns and this was programming downshift issue. In other words, when you put your foot to the floor it is trying to learn what the optimal gear is. I was kind of surprised by that and didn't buy it. I agreed to keep an eye on it.

The weird part is the rest of the car drives great.
Nope, the additional gear is 2nd, the locking torque converter has nothing to so with gear ratios.
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Old 01-15-2011, 10:51 AM
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Re: HEMI hestitated and "shook" during W.O.T.

If you were running at 45 in Eco mode, it almost sounds like there was a delay for all eight cylinders to kick in, thus the full throttle 4 cylinder shutter.
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Old 01-15-2011, 11:10 AM
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Re: HEMI hestitated and "shook" during W.O.T.

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Originally Posted by mwhited View Post
If you were running at 45 in Eco mode, it almost sounds like there was a delay for all eight cylinders to kick in, thus the full throttle 4 cylinder shutter.
Hmm, I don't think it has anything to with MDS or the engine for that matter, it's the good ole' 545RFE torque management doing it's thing. I think the OP's problem will lessen over time.

And FWIW I believe it's the 3rd gear that is different.

check this out guys: go to an open non traffic area and floor it from 0 going into at least 3rd gear, when you do this in normal "D" mode everything is normal.... but when you do this in autostick mode you'll notice 3rd gear is very different, when the change from 2nd to 3rd occurs 3rd starts off at a much higher RPM, it's pretty cool, try it out sometime and remember, you gotta be going WOT so don't be a pussy.
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Old 01-15-2011, 11:38 AM
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Re: HEMI hestitated and "shook" during W.O.T.

Quote:
Originally Posted by 5.7Unlimited View Post
Hmm, I don't think it has anything to with MDS or the engine for that matter, it's the good ole' 545RFE torque management doing it's thing. I think the OP's problem will lessen over time.

And FWIW I believe it's the 3rd gear that is different.

check this out guys: go to an open non traffic area and floor it from 0 going into at least 3rd gear, when you do this in normal "D" mode everything is normal.... but when you do this in autostick mode you'll notice 3rd gear is very different, when the change from 2nd to 3rd occurs 3rd starts off at a much higher RPM, it's pretty cool, try it out sometime and remember, you gotta be going WOT so don't be a pussy.
Nope, it's 2nd gear that's different, it's called 2 Prime.

545RFE Automatic Transmission

The introduction of the completely redesigned 1999 WJ Grand Cherokee in June of 1998 was a much anticipated date for automotive enthusiasts. One of the major pieces of the redesign was the new five speed automatic transmission designated the 545RFE. This transmission was developed specifically with Jeeps in mind.
This transmission was available only on WJs with a 4.7L V8 engine; the 6 cylinder engine received the venerable 42RE. By design, the 545RFE is quite sophisticated. It employs multiple gear ranges controlled electronically to provide greater fuel economy as well as great responsiveness for passing and acceleration. Precision engineering and manufacturing methods also helped to reduce overall NVH (noise, vibration, harshness). It features five forward gear ratios with an alternative second gear ratio (2 Prime) for smoother 4th to 2nd kickdowns at high speeds to provide spectacular passing performance over a wider speed range. The addition of the fifth (overdrive) gear ratio is the primary cause of the lower NVH and better fuel economy (lower RPMs = less noise and fuel consumption).
It is electronically controlled by the TCM or Transmission Control Module. This module is the heart adaptive shifting programming. The TCM depends on data from several sensors and switches to determine driver demand and the Jeep's operating conditions. Controls are in place to protect the transmission from damage from high temperatures. The TCM protects the transmission by modifying shift schedules, line pressure and converter clutch control. These controls reduce the amount of heat that is created and increase cooling of the 545RFE. The 545RFE is contained by a one-piece die-cast aluminum case. To reduce NVH, integrated into the case are ribs to increase multi-angular torsional rigidity. There are dual lubricant filters in the 545RFE. First is the customary internal main sump pan filter; second is the external canister-type pump return filter.




Gear Ratio 1st 3.00 : 1 2nd 1.67 : 1 2nd Prime 1.50 : 1 3rd 1.00 : 1 4th 0.75 : 1 5th 0.67 : 1 Reverse 3.00 : 1 Torque Converter Up to 2.40 : 1
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