I recently created a new topic thinking that my '02 Buick Park Ave Ultra with 89,000 miles was having tranny hard shifting problems that were related to tranny temperature...
But yesterday the car had only been driven for 15 minutes and the coolant temp was 180 degrees and the outside air temp was 65 degrees, and while in overdrive on the freeway I accelerated to pass someone. From that point forward, every shift was abrupt. The engine light did not turn on at all.

A little while later I pulled over and shut off the engine. I waited only a few seconds and then started it again and continued driving. Shifting was normal the rest of the way home. How does that make any sense? Whatever the problem is, it doesn't appear to be heat related.

When I got home, I checked for error codes using my Actron scan tool and my Innova scan tool. There were no error codes.

The hard-shifting behavior has occurred twice since I've owned this car - once almost a month ago when I was stuck in traffic for more than an hour, and then again yesterday when traffic was clear. So it'* not a frequent problem (yet).

I've been contemplating installing the Transgo shift kit and scuffing-up the walls of the accumulator as recommended by others, but it now seems like the cause of the problem may be downshifting, and installing the Transgo kit will only affect 1-2 and 2-3 shifting, right?

Any ideas?
Thanks.

Could be a bad trans or motor mount. Could also be a sticking shift accumulator. Look in techinfo/transmissions and in the 4t65e you will find how to install a **** kit in a 4t65e It will tell you how to remove the accumulator and then you just lightly sand the cylinder walls with a very fine sand paper. I've cleaned up a ton of hard shifts this way.

I did a DanThurs inspired shift kit, filter change and Dextron VI upgrade on a 2001 SSEi with 95,000 miles and shifting horrible, thought the tranny was going to crunch itself at any moment. SSEi now has 155,000 miles and running great. I am so happy I did the shift kit and fluid upgrade over spending big bucks on a rebuilt transmission.

On a side not, I had a plug wire go bad at 145,000 miles and it started to shift poorly. I discovered that if the engine is not running properly, it makes the tranny shift poorly also.... After plug wire was replaced, tranny shifted normaly again.

Moved to Mechanical/Buick as we try to keep keep these mechanical threads in an order that helps visibility and people doing searches for like problems. Park Ave will be getting it'* own section inside Buick soon. V

EDIT: Park Avenue Section created. And this thread moved into it. Moderators please move all Park Avenue related threads from Buick here as time permits and lets keep up with our getting "Brands/Models Organized Initiative".

So, Dan, if this was your car, would you install a 'DanThurs inspired shift kit', change the filter, and fill with Dextron VI? Has there been long-term shift harshness correction success installing the spacers from the hardware store, scuffing-up the accumulator walls, and changing the filter and fluid, but not replacing the springs?

I wonder what the spacers in the TransGo shift kit are made of; if I choose to buy and install spacers from the hardware store instead, I'd be very reluctant to use nylon.

Or would you install the TransGo shift kit (including the springs), scuff-up the accumulator walls, and change the filter and fluid?

Thanks!

I've had great luck simply making shift kits. Both billboost and i have made dozens for members. The springs are nice, but don't really make a real big difference. I replaced my springs and went with double springs. And I find it really don't shift much different then simply adding the spacers.

Thanks, Dan.

So is adding the spacers the most important factor, or is scuffing-up the cylinders in the accumulator also very important in fixing the hard shifts?

And have the aluminum spacers from the hardware store held up well, or have you found that aluminum is too soft?

Scuffing the cylinder walls up is what really fixes the problem. But only scuff it a little bit, take the shine off. What happens is the O rings stick, pressure builds up and then it lets go causing a very rapid and harsh shift. Think of it as a bungee pressure builds on one side pushing the piston down which moves fluid nice and smoothly to close the shift band. Do it slow and you have a smooth shift. Do it fast and you have a hard shift. Adding the spacers will not make the shift harsh, but will shorten the shift time, making it firm, but not harsh. You can make the spacers a bit larger and that will start to make them harsh. You can make them a bit shorter and it will make them a big less firm.

Never tried aluminum spacers, but it should be OK, I've used steel and plastic with no difference in the two.

Hi Dan,
I bought 8 quarts of Dexron III fluid and a filter, but I haven't been able to find the right size spacers at the hardware store (Home Depot and Lowes). Any ideas where I can find the spacers here in So. Ca?

Thanks!

You may have set a P1811, which is a bad pressure control solenoid.
I have noticed that all scan tools are not created equal. I have scanned vehicles with different scan tools and got different codes.
You may want to try scanning the car with a different scan tool to see if the P1811 was actually set. P1811 will not set a check engine l
ight.