What would cause a 4l60e to shift early
What would cause a 4l60e to shift early My car is shifting about 400rpms sooner than it should be, also my rev limiter dropped, and the car is lacking some power. Could this be a transmission issue?
Moderator
Joined: Aug 2010
Posts: 7,323
Likes: 529
From: Ann Arbor, MI
The PCM controls the shifting. A bad transmission typically shift too late, not too early.
This sounds like an engine sensor problem - the PCM does not think you are at WOT. I would check the MAF and TPS first, then the MAP.
This sounds like an engine sensor problem - the PCM does not think you are at WOT. I would check the MAF and TPS first, then the MAP.
I have replaced the tps and maf, so I will work on relpacing the map sensor. Out of all curiosity could this problem have anything to with speed sensors or the fact that the abs is unplugged in my car and it still has the abs distribution block?
Changed my map sensor and it's still the same. It's supposed to shift at 6700 for all shifts, but it shifts at 5800 at the 1-2 shift and around 63/6400 on the 2-3 and will shift at 6700 at 3-4. Is it the trans?
Moderator
Joined: Aug 2010
Posts: 7,323
Likes: 529
From: Ann Arbor, MI
The 4L60E has no ability to shift on its own. Shifting is completely controlled by the PCM based on sensor input and the "shift tables" in the tune. Of the sensors, the VSS and TPS are the most critical. I suggest hooking up a scanner that can read TPS position and ensuring that it reads at least 98% with the pedal all the way down.
Trending Topics
Moderator
Joined: Aug 2010
Posts: 7,323
Likes: 529
From: Ann Arbor, MI
You seem to be checking all the right things. Yes if the speedometer reads correctly the VSS should be right, and yes the VSS is located in the tailshaft.
Unless the tune changed, the rev limit is not going to change on its own. Maybe your tach is wrong. Can you compare the tach with a scanner?
Unless the tune changed, the rev limit is not going to change on its own. Maybe your tach is wrong. Can you compare the tach with a scanner?
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo The scanner I used was my cousins snap on scanner not sure what model I will ask him and see if it will read rpms. I do have an autometer shift light with built in tach though and that's what I'm going by.
Are you seeing any immature codes at all? Or any that
are set to no MIL, rather than No Error Reported? Short
shifting is a fault response to several things when the
PCM doesn't know what to trust (VSS, TPS, etc.). But
these shift RPM numbers don't seem like that kind of
conservative.
Now these RPM values you say, are they from logs
or from eyeballing the notoriusly slow and inaccurate
tach?
are set to no MIL, rather than No Error Reported? Short
shifting is a fault response to several things when the
PCM doesn't know what to trust (VSS, TPS, etc.). But
these shift RPM numbers don't seem like that kind of
conservative.
Now these RPM values you say, are they from logs
or from eyeballing the notoriusly slow and inaccurate
tach?
I did have a maf low voltage code I think it was. But I replaced the maf and the light did not come back on.
The tach I'm going off of is the autometer digital shift light I have with peak recall
The tach I'm going off of is the autometer digital shift light I have with peak recall
The trans as stated cannot shift on its own so very unlikely a trans issue. and as stated many variables but I would have to agree its a sensor issue of some sort.
__________________
I'm not sure what sensors to look at anymore or replace. Which all are trans related? It may all be in my head at this point but it feels sluggish like its slipping. But I would much rather it be a sensor problem if I could just figure it out.
same problem I have the same thing but only in my 1st to 2nd shift programmed at 6000 and 37 with 3.73s but shifts at 5500 at 35 would love to here some possible solutions 2nd to 3rd 5900 at 75 is right on
