Mr. Trick

iTrader: (19)

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?

mrvedit

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.

Mr. Trick

iTrader: (19)

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?

mrvedit

The VSS (speed sensor) is critical in determining when the trans shifts.
Sorry, but I do not know the answer to your ABS question.

Mr. Trick

iTrader: (19)

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?

mrvedit

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.

Mr. Trick

iTrader: (19)

It's has a new tps sensor and reads 99% at wot. My speedometer is good so my vss should be good to right? Also the vss is located in the tailshaft correct.

mrvedit

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?

Mr. Trick

iTrader: (19)

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.

jimmyblue

iTrader: (11)

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?

Mr. Trick

iTrader: (19)

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

performabuilt

iTrader: (25)

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.

Mr. Trick

iTrader: (19)

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.

2000 TA owner

iTrader: (1)

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

Mavn

iTrader: (3)

I'm thinking your tire size is off in the tune... Or gear ratio etc