Just bought another 2002 Grand Prix GT Problem

[GaryFenza]

This is my third Grand Prix with the SAME EXACT damn annoying problem. The engine runs perfect, the car sounds good when accelerating. (92,000 miles) I dont understand i'll be going down the road shifting good, then slow down and make a left hand turn going about 15mph or less and it shifts rough into gear and then from that point on all the shifts are hard and you feel the "kick" of the shift in your seat. Then i'll turn off the ignition, and it will be find, and enentually it starts doing it again. anyone have any idea what the hell this is?

[BNaylor]

Get it scanned with a trans capable scanner and see if a P1811 (max adapt, long shift) DTC has set. It commands maximum line pressure and disables shift adapts which then causes the hard shifting, mainly upshifts. Does not trigger the SES/CEL light. It could be internal slippage, worn 2/3 clutch packs, accumulator, or a pressure control solenoid (PCS) issue.

[GaryFenza]

Thanks, i put some Lucus Transmission FLuid stuff in it.....in the past this stuff has worked for me, so i figured i would try it again. If it is a computer problem like the Codes, how much does that cost for a place to fix that problem.

[BNaylor]

How DIY capable are you on autotransaxles? Can you do a pan drop service? I have a fix that may work. You're welcome to try it versus spending the big bucks.

[GaryFenza]

yea i did a pan drop to change the fluid and filter on my other 03 Grand Prix, why what should i do on this one....drop the pan and put a new filter and fluid in?

[BNaylor]

See link below. You'll find the fix and results surprising. Basically the fix is a 1-2, 2-3 accumulator mod by adding a shift kit with new screen filter and upgrading to the new Dexron VI. The shift kit insures the PCM does not see shift timing greater than .65 seconds, thereby eliminating the P1811 DTC and the hard shifting. The Dex VI is better than the old Dex III with better lubrication qualities and temperature control since it is a synthetic blend ATF.

Click here

[GaryFenza]

Thanks, so i drop the pan.....put the new Dexron in, replace the filter and take the accumlator down by the bolts should, then dissaemble it and put the new springs and internals in? can i get further instructions please, thanks

[BNaylor]

I recommend getting the ZZP shift kit which will have the accumulator spacers. $30.00. Plus the instructions are the best around so hard to screw the job up. Let me know if you need a link. Also, the ZZP kit comes with a new screen filter. The SPX/Filtran which is the same one as the GM/AC Delco TF304.

First step is pan drop, then do the accumulator mod and reinstall, new screen filter, close it up and then add the Dex VI, approximately 7.5 qts give or take a few ounces.