Pontiac Repair: 4-speed Auotmatic Transmission, piston seal, speed transmissions

Question
QUESTION: I recently changed the AT fluid and filter on a 2001 Pontiac Grand-Am. All is well except I now have a complaint that the transmission takes longer to shift from park to reverse and from reverse to drive.  I test drove it and the delay is about 1-1/2 seconds. Aside from that it shifts fine and there is no other abnormality.  I am told the transission had no delay in shifting before the fluid and filter change.  I am certain the level is correct and I used a quality brand Dextron III fluid.  Any comments or suggestions???

ANSWER: Hi colin:

Does this happen on first shift "garage shift" in the AM or all the time? any other complaint like loss of drive on sharp turns? that would indicate a low fluid level or the filter may not be sealing good in the case. Other then that I don't know of anything else that could have caused this to happen all the sudden. If it's not either of those things then it has an internal leak leak and the "gear" is taking to long to fill up it could be a bad piston seal leaking or just plain worn out cluthes in that gear.
Good luck:)


---------- FOLLOW-UP ----------

QUESTION: The delay occurs regardless of cycle or temperature and does not change from cold to hot.  At 1 1/2 seconds, I don't consider it excessive unless it gets worse.  Question: what is the difference between Dextron III and IV
What models is the D-IV used on and is it interchangeable with the D-III.  One last question: What systems are monitored by the "Check Vehicle" MIL? (not only for the 2001 Grand-Am but newer vehicles as well)

Answer
dextron IV is the newest one out and it back dates all other dextron's. It's more for the asain warner transmissions in the newer gm cars like the g6 and the torrent's with the 5 speed transmissions. you can mix them without an issue. Do not mix ford mercon and dextron that's bad.

The Body control module is what trips the SVS lamp on but the BCM monitors a lot of things a ABS issue will turn on the SVS lamp or a headlmap bulb out will turn the lamp on. The BCM monitors all the serial data from the modules and if any module has a fault depending on what that fault is it wil decide to trip the lamp on or not.