2000 Century shifting hard

Hello,
Me again. :) Another problem that I don't know if it's too urgent or not. '00 Century, 76K miles, 3.1 V6 engine. Sometimes it'll shift hard, like I can kinda feel it jerk a little when it shifts -- ONLY when it's been good and warmed up, like driving on the interstate for 3+ hours when it's above 50 or so degrees outside. Is this a sign that my tranny's in the early stages of going? Can those fluid additives help, one that's supposed to fix hard shifting (I see the Lucas brand in the store, but mechanic also suggested some brand like BJ's or BG's or something?) Do you have any experience or suggestions of what might work for this?

Some more info that might be relevant: Hometown mechanic drove it a couple weeks ago and said, he's not sure if he feels the hard shifting or not, might just be normal, but he did feel that my car doesn't want to shift all the way down into first, like when I take off from an idle, it's in second already. (Well, he could make it go into 1st if he really floored it taking off on an uphill stretch, but just from a regular start, he said it felt like 2nd.) What would make it do that? He suggested it was some valves sticking inside, and said to try a fluid additive. I got the fluid changed about 16K miles ago, so we don't think it's an old-fluid problem. I'm going to try to take it somewhere with free diagnostics and see if he'll plug his computer in to check if it's going through all the gears.

Thanks so much for any help!

The first thing to do is to make sure the fluid level is correct. If you intend to use an additive I suggest using Seafoam for transmissions. It will help to remove some of the build-up in the transmission, if there is any, and can help free any sticking solenoids. If shifting becomes extremely hard you may be developing a problem with the pressure control solenoid which is about a $500 repair. If you have a tranny shop diagnose it they will be able to point you in the right direction.

See this reference- http://www.automotiveforums.com/vbulletin/showthread.php?t=899929 BNaylor, an AF Moderator, helped me with much the same problem with this advice. A very easy fix, and lots cheaper than solenoid replacement, which evidently doesn't last. Hope this helps.

See this reference- http://www.automotiveforums.com/vbulletin/showthread.php?t=899929 BNaylor, an AF Moderator, helped me with much the same problem with this advice. A very easy fix, and lots cheaper than solenoid replacement, which evidently doesn't last. Hope this helps.

Hey Dogtooth,
You are the man! Nice link! Thank you!:)

Hi Lewisp

I have the exact same problem and almost the exact mileage as you. It is in fact, the pcs solenoid, a $600+ fix. Don't worry too much about it though, I have been driving it this way for 3 years, almost 40,000 miles! But do take a look at dogtooth's excellent post for some more info. Really, don't run out and spend money--you have plenty of time.

Thanks all!

Glad to help! Please let us know how things go for you. The shift kit and fluid change have now been working for 3,500+ miles in my wife's '04 Century with nary a rough shift. A tip of the hat to BNaylor again! Now if we could just get him to come up with a fix for GM's troubles ...