I know this should be in my signature, but in case it'* outdated or just missing, here goes:

2003 Bonneville SSEi
~132,000 miles

I have a few problems with the car right now. The first is a relatively simple fix, but I am short on cash right now so I am waiting. The SES is lit, checked it a while back and it was the Catalytic Converter (P1141 I think, but cannot remember). It has been getting worse lately and I really need to get it fixed- it rattles like anything.

The second question is that the "Service Stability System" light comes on here and there. It came on once, left for a few months, and now it'* coming on here and there- usually while taking small turns or hitting a bump. Not sure what would cause this...

My BIG problem though, is that every so often the car shifts VERY hard. I mean it really slams into gear. When it happens, it happens in ALL gears, not just one or two. It first happened probably a little over a year ago- after a very long drive on a hot day. After that period, I'd get smaller bangs here and there, but only on take off and usually around turns. It felt kind of like the tires slipping and suddenly grabbing. I had old tires, so I replaced them, drained the fluid in the tranny, changed the filter, cleaned the pan, refilled it, and off I went. No more problems. I attributed to balding tires (maybe erroneously).

Well, I now have about 35,000 miles on the tires, and they're getting older but not at all bald yet. Ahout 6 weeks ago I was driving and the banging started up again. I was pissed that my tires could be balding so soon- so I rotated them and checked the tread and it should be fine. Now it'* becoming more frequent. It seems to happen mostly after long drives or starting numerous times (like going to 4 different stores for instance). I will be driving and suddenly every shift is like hitting a wall. Power is obviously lacking when this happens. It will continue to happen until I shut off the car- so if I'm in a row of stop lights every time I accelerate after a stop it bangs through all gears.

The WEIRD thing is that stopping the car and letting it cool down completely eliminates the problem. Other than when this is happening the car shifts like butter- I couldn't imagine better shifting. The fluid has about 30,000 miles on it and I will probably change it, but it'* still pretty red. It is Valvoline Synthetic ATF. I have also noticed that when parked and idling on an upward slope, the car sometimes emits a bad odor (some kind of burning (?) fluid? The other thing I question is whether or not it is really the shifts that cause it to slam, or the throttle. It ONLY slams when I am giving it gas. I understand the car won't shift up without gas, but even backing off before a shift, and then giving it gas will slam the car. It does NOT slam when downshifting.

The reason I posted all of the problems is that I'm wondering- is this definately a tranny problem, or could this be some kind of backpressure problem? I'm short on cash and the "Service Stability System" light and this problem have me a bit concerned....

Thanks, as always, for the help and advice guys.

Some experts can chime in here but the cat convertor can cause havoc with the way the car runs. The sensors are getting buggered up with the crap the cat is pushing back into the engine. Scan the car again and see if another code comes up but I would be looking at the cat myself.

I am no expert but I have had a cat go bad on me before and the problems it created seemed unrelated but once the cat was changed the car ran great again.

Is it the money for the cat you don't have or the money for labor. You might be able to find someone to help change it out for ya. Someone near u.

may be unrelated but also check your front motor mount. have some one power brake the car lighty while you watch for the amount of play. although I doubt this is your problem it could make the rough shifts feel and sound worse.

Windshield,
Thanks for the reply, I was hoping to hear that- but don't want to be too optimistic. I am kind of torn on the cat- I am between going direct fit and universal fit. I'm thinking I'd like a hi-flow cat, but cannot find a direct fit. I know the highly recomended Magna Flow Universal Fit High Flow Cat is available for less than $70 on EBay, which I could afford.

The labor involved may become the issue. I wouldn't even work on cars if I could find a GOOD mechanic around here (Cape Cod), but I've been unlucky. I just started doing it myself. It usually costs too much to go to a mechanic and you never know what corners they cut until it'* too late. I may not know what I'm doing, but I'll find out and do it right or have myself to blame I guess.

I was thinking of maybe cutting out the old cat myself, installing the new one myself, and then just driving it straight to some place to weld it all together (i've never welded before). Or I may find someone who knows how to weld and has done this before to help...I'm just not sure which way I want to go yet. Suggestions would be appreciated.

The only tip I could give you would be to go to your local NAPA auto parts store. Ask them for a price and a recomendation for a shop. In my expierence NAPA has not led me astray.

True test of a shop isn't the price or the look of the place or the size it'* how they treat you. I go to a place with 2 bays. They are busier than a one armed paper hanger with an itch. I got the recomendation from NAPA and had to send my wife as I was in NJ in jail. The shop treated my wife with respect and to me that means alot. It also shows they aren't there to rip anyone off. They do all my work now if it'* something I can't do myself. I send everybody there.

Just my 2 cents

Also smaller shops are more willing to help with the little things like welding after u started the work.

The harsh shifting could be the pressure control solenoid in the transmission. Here'* a similar thread.

http://www.bonnevilleclub.com/forum/...ic.php?t=71558

You can try changing the fluid first, and put in standard tranny fluid. Some have had shifting issues when using the synthetic fluids.

Getting the cat replaced could take care of a host of performance problems.

The service stability could be a bad wheel bearing, but first check the wheel speed sensor connections front and rear.
Do you feel a clunk or hear a differance in noise when you turn the wheel while going over a bump?

Everyone, thank you for your replies. A few weeks ago, right after I rotated my tires I noticed a strange noise in the front end going over speed bumps, but it has gone away. I thought it may be a wheel bearing too.

I know the CAT needs to be replaced, so I am going to grab one of the universal high-flow models and have it welded on. I will see if this fixes the clunking gear shifting problem. My next move will be the steering wheel position sensor and a good look at the bearings. It probably won't happen too soon though- but as I get the money I'll do it.

Thanks again guys! You've been a big help.

Does the transmission have a limp mode when it detects some error codes? I seem to remember that from somewhere. I wonder if the unmodulated shifts are a symptom of the limp home mode...?

I don't think these transmissions have a default or "limp home" mode.