limp mode and converter
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Teching In
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From: calif
limp mode and converter doin 55 on the freeway heard or felt something next thing rpm's are 5000 and it's in overdrive , let off the gas it feels like it's freewheeling .. get off the freeway stop , it's got f and revs in all shift modes , so take off starts in first and shifts into second but thats it,felt like it shifted fine from first and second .. felt some vibration when coming to a stop but pulled and shifted to second all the way home ... never got hot, fluid clear and not burnt .. now home in the driveway still had f and r but had a vibration in neutral and in park ... shifted from f and r and back a few times power braking some times didnt feel like it grabbed hard , making some noise from the trans dont sure what ... then had no f or r but the vibrations were gone ... thinking the converter went bad and the trans went in limp mode ?????? if thats possible ?? help please ...
Last edited by xracer33; Apr 30, 2016 at 05:26 PM.
Thread Starter
Teching In
Joined: Apr 2015
Posts: 41
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From: calif
starts in first and shifts into second but thats it ... does not shift past second. had a vibration in park and neutral like something was out of balance, once it lost all gears the vibration was gone too ... does a 4l60 have a limp mode ???
TECH Junkie
Joined: May 2012
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From: Poplarville, MS
Input shaft and input drum are spinning in park. When the 4L60E goes into limp mode the trans will only have 3rd gear and reverse. Being that you have 1st and 2nd gear, I would say that the trans is not in limp mode. Most likely something has broken in the input drum.
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Verdad Gallardo TECH Junkie
Joined: May 2012
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From: Poplarville, MS
We did guess that something has broken in the input drum, but there is no way of knowing until the trans is taken apart. It really makes no difference. The trans still has to come apart and that is a guess based on the description that you gave. Need more info for a more pinpointed guess. Like what gear is the shifter in when freewheeling in second?
Joined: Aug 2007
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From: Turnin' Wrenches Infractions: 005
Joined: Aug 2007
Posts: 24,241
Likes: 89
From: Turnin' Wrenches Infractions: 005
Well false means its not true. The computer will shut off solenoids if certain faults codes are tripped, which cause irratic combinations of gears available. My particular fault that plagued me was leaving me with 2/3, no 1st, 4th, or lockup. Others are available. The info is available in the trans sticky, particulary the post that performabuilt made that is linked up there.
TECH Junkie
Joined: May 2012
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From: Poplarville, MS
My understanding is that limp mode is when both shift solenoids are turned off by the PCM or the trans loses power to the solenoids or loses communication with the PMC to the extent that both shift solenoids do not turn on in any combination. My terminology and yours may be a little different, but there is no need for name calling and rudeness. We are all just trying to help the op. I am not a “Bad poster”.
Moderator
Joined: Aug 2010
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From: Ann Arbor, MI
Guys, you are splitting hairs and arguing over definitions; this will confuse the less experienced members and future readers. Both of you are very knowledgeable and great contributors to this forum.
My inclination to delete this group of 4 posts (inc this one) and combine what both of you are saying into one post. Cool?
My inclination to delete this group of 4 posts (inc this one) and combine what both of you are saying into one post. Cool?
Joined: Aug 2007
Posts: 24,241
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From: Turnin' Wrenches Infractions: 005
Well lots of people take whats here as gospel, especially when said with authority. I explained my particular issue, which ive even explained in lots of detail over the years as I learned how to make it happen and avoid it by understanding what actually was happening. In a nutshell, the computer sets codes for different reasons based on trans performance and sets you in a limp home mode based on the code set. Its intention is exactly as it sounds....it keeps the car driveable with the malfunction. Sometimes these are false, sometimes they arent. But the point I was making is there are several different versions (based on which code is set). Saying there is only one variation is flat wrong and shouldnt be said. Only having 3rd and reverse is what it's like when the trans has NO power correct? And that may be able to be commanded also I dont know for sure cause I'm not a trans guy.
Joined: Aug 2007
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From: Turnin' Wrenches Infractions: 005
See here: https://ls1tech.com/forums/automatic...lush-more.html
Now, based on the below information, can YOU tell me which trans code I was fighting??
* P0751 - 1-2 Shift Solenoid Valve Performance - No First or Fourth Gear
* P0752 - 1-2 Shift Solenoid Valve Performance - No Second or Third Gear
* P0753 - 1-2 Shift Solenoid Circuit Electrical
* P0754 - Shift Solenoid A Intermittent
* P0755 - Shift Solenoid B Malfunction
* P0756 - 2-3 Shift Solenoid Valve Performance - No First or Second Gear
* P0757 - 2-3 Shift Solenoid Valve Performance - No Third or Fourth Gear
See, we are learning today aren't we???
So, to be correct, it should have read......When the 4L60E has no power the trans will only have 3rd gear and reverse.
Now, based on the below information, can YOU tell me which trans code I was fighting??
* P0751 - 1-2 Shift Solenoid Valve Performance - No First or Fourth Gear
* P0752 - 1-2 Shift Solenoid Valve Performance - No Second or Third Gear
* P0753 - 1-2 Shift Solenoid Circuit Electrical
* P0754 - Shift Solenoid A Intermittent
* P0755 - Shift Solenoid B Malfunction
* P0756 - 2-3 Shift Solenoid Valve Performance - No First or Second Gear
* P0757 - 2-3 Shift Solenoid Valve Performance - No Third or Fourth Gear
See, we are learning today aren't we???
So, to be correct, it should have read......When the 4L60E has no power the trans will only have 3rd gear and reverse.
Moderator
Joined: Aug 2010
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From: Ann Arbor, MI
Thank you for the excellent info and saving me the trouble of copying it in here.
I'll verify, but I think the GM doco does refer to the PCM entering "limp mode" for the transmission and then only 3rd and Reverse are available. Limp mode is very similar to the trans not having any power, e.g. with the connector removed.
I'm still trying to determine if 1st gear is available in "limp mode" (or connector removed) if the shifter is moved to [D1].
I'll verify, but I think the GM doco does refer to the PCM entering "limp mode" for the transmission and then only 3rd and Reverse are available. Limp mode is very similar to the trans not having any power, e.g. with the connector removed.
I'm still trying to determine if 1st gear is available in "limp mode" (or connector removed) if the shifter is moved to [D1].