2003 Buick Lasabre transmission hard shift

I have a transmission issue that I would like to get some help with. My 2003 Buick Lasabre - 3.8 Ltr. - 197,000 miles has a P1811 pressure control code which produces a long and/or hard shift through all of the gears, on the 4T65E transmission.

It shifts perfectly most of the time and then it will go into hard shifting. It does seem to long shift, but very rarely.

The dip stick pops out of the down position; However, the fluid level is correct and what I think is a vent, on the top of the casing, appears free and open. The transmission has no external leaks. When I check the fluid, using the method highlighted in the owner's manual, I noticed a few bubbles on the dip stick, but not foam.

My research tells me that the problem is the pressure control module, which requires removing the transmission or extensive dismantling, to access the side cover of the tranny, to gain access to the modules.

Another repair I've found is installing a shift kit (spacers & springs) that is accessible by removing the bottom pan and accumulator cover. My questions are:

1. Are there any simple things to check, other than the module or internal transmission issues, that could cause these issues?

2. Would you try the shift kit first, as I have read that this can correct the shifting issue without extensive effort.

3. With 197,000 miles on this vehicle and the fluid/filter has never been changed, would you replace the tranny fluid or put the old back in. I've read that new fluid could cause an old transmission to start slipping.

4. If I am forced to change the pressure control module, what should I expect to pay for that repair.

Please let me know and thanks in advance for your professional help!

cashtom55

Replacing the springs and collars for the 1-2/2-3 accumulators in the oil pan along with the differential tube enhancement and a flush with clean Dex 6 can help alleviate the P1811. It's worth the effort for the minimal cost, along with replacing the filter in the process.

If the trans has to be opened to replace the PCS solenoid, it might as well be rebuilt completely since the parts cost is small compared to the labor. The stovepipe (reverse reaction drum), chain, a few other critical valve spools, the input shaft spline, and bands may all be exhibiting wear at almost 200K miles even if the stacked clutches and plates all have normal or minimal wear.

$2,000-2,500 is a typical turn-key R&R with rebuild and a warranty. If the trans is pulled to just go through the valve body, it might be $500-700 less at most.

Had the same issue with a 2003 Lesabre I owned, at about 150k. If I shut it off, when restarted it usually went back to normal. Never fixed it and sold the car, 30k later.

TransGo Shift kit worked wonders for my tranny!!!!!

Used to live on Grand ave, south of sunrise in the 60's.

Fresh fluid might work wonders… I would not do a flush with that mileage though, just a spill and fill and a filter change if you have to drop the pan.