QuestionQUESTION: I have a 1999 Cadillac Seville STS, w/ the 4.6L V8 Northstar motor & 4T80-E trans.
The engine and trans were out for lower crankcase oil seal replacement.
Everything went back in and the car runs great. The only problem is that (in any gear) if you hit the gas pedal and keep it on the floor, it'll first downshift into "passing gear" (as it should) but then as it reaches the redline (6500) it doesn't shift, just keeps going into the red.
If I release the gas pedal just a touch when it gets near the redline, it'll shift into the next gear and all's good.
Before, it always shifted at the redline. The trans shifts normally in every other kind of driving and it's all smooth, it goes into all the different gears when it's supposed to. It's only when you floor it and keep it
floored that it won't shift at the redline.
I've checked for codes (I can access everything, ABS, transmission, airbag, etc. not just PCM) and there are none. The car runs perfectly otherwise and since this problem started I've changed the trans fluid/filters and the fluid is at the right level.
Please help!
Thanks,
Jad
ANSWER: Try adjusting your transmission throttle cable.
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QUESTION: This transmission is electronically controlled - no throttle cable.
ANSWER: My apologies, Was NOT thinking clearly when I answered your question as I am still shocked over the death of my 59 year old sister from a massive heart attack last week.
Anyway, You have 3 possibilities:
1. The TFP (trans Fluid pressure) manual position switch on the lower valve body of the trans can be faulty and or have sticking pressure switches.
2. A sticking pressure regulator boost valve.
3. A circuit malfunction in the lateral accelerometer.
IS or HAS the check engine or any service messages appeared on the dash while driving the vehicle ?.
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QUESTION: No need for apologies, my condolences for your sister.
Absolutely no codes, no CEL or other service messages while driving or otherwise. I took the plunge today and kept my foot on the gas into the red and at 6700 or 6800 it shifted. Did it twice at the same spot, and the shift was smooth, nothing unusual. It used to shift at around 6250 actually. I read that the rev limiter is at 6800 and I didn't feel any fuel cut off so I don't think I actually hit 6800. What could change the shift point for full throttle acceleration? The computer was not touched (other than being disconnected for a while, of course). Thanks for your help here.
AnswerIt is difficult to determine exactly what the fault could be, As anytime you open an electrical connection and it remains open for a period of days or weeks corrosion can start to occur on the pin connectors causing a difference in resistance readings which can cause this problem. When the trans was removed a small piece of debris could be causing one of the pressure manual position switch to change in the amount of pressure required to close the contacts. A slight variation in the throttle positioning switch may have occured while wrestling with the engine. .
I really would not be to concerned about it unless the trans does not shift prior to the limiter kicking in.
