PontiacBonnevilleClub.com

I'm not sure what my goal is in posting this, maybe just feedback if anyone has any;

I had my transmission fully rebuilt last June. The trans now has 31k (kilometers) (just shy of 20k miles) on it and it feels like the torque converter is shot again. At highway speeds (100km/hr to 120km/hr) I'm getting stumbling/bucking when attempting light acceleration or just maintaining speed.

It not totally consistent at the moment but I expect it to get worse.

So can anyone think of why this would happen? Of course I'm past my warranty on it so I don't think I'm going to have much luck there. Are the transmissions and components like the torque converter on the SSEis really that weak? Or does this sound more like a defective part and/or a bad rebuild?

All I know is that if I get this rebuilt again (likely elsewhere as this place put my boat roller mount on upside down leaving it sticking out the bottom of the car several inches) it had better last for several years or I might as well look for another car.

Any input is appreciated. Even if it's just a theory.

Thank you

This isn't a transmission issue, this is an ignition system issue.

When I first had this problem, new ignition wires solved it. When it came back again a month ago, new coils solved it.

I would replace your plugs and wires to start, then the coils, then the ignition control module. Cleaning the MAF sensor wouldn't hurt either.

nos4blood70 wrote:This isn't a transmission issue, this is an ignition system issue.

When I first had this problem, new ignition wires solved it. When it came back again a month ago, new coils solved it.

I would replace your plugs and wires to start, then the coils, then the ignition control module. Cleaning the MAF sensor wouldn't hurt either.

If you're right, I would be thrilled. And you can bet I'll be back in here thanking you.

I replaced the coil packs, wires and plugs last year already with top quality parts.

The only thing I haven't replaced is the ICM, which I was suspicious of at the time when a misfire was diagnosed due to my past experience with the ICM in my Camaro, but the new coil packs seemed to solve it.

I'm ordering one right now. <$200 is a lot better than a 4k bill. Might as well give it a shot.

Thanks for the input!

I recommend Amazon, or something similar, where a return wouldn't be too much of a problem.

You didn't use platinum plugs by chance did you?

nos4blood70 wrote:I recommend Amazon, or something similar, where a return wouldn't be too much of a problem.

You didn't use platinum plugs by chance did you?

Went with RockAuto. They're usually pretty good with returns.

No, I used Iridium NGKs to replace the OEs.

So, I got a new ICM, installed it, and it seemed like the problem was solved for about 24hrs.

Now I'm right back where I was before I installed it. Same stumbling, etc.

I feel like there's something wrong with the ignition system but I've literally replaced every component at this point. I'd pull it all apart but it's freezing cold outside with snow everywhere, and my garage is already occupied.

I may just bring it into my mechanic in the near future.

If you have security torx bits, get some MAF cleaner and clean the filament on the MAF. One last quick ditch effort

nos4blood70 wrote:If you have security torx bits, get some MAF cleaner and clean the filament on the MAF. One last quick ditch effort

I just cleaned that sucker last summer, but it's easy enough to do. Not like I have anything to lose.

Thanks, I'll give it a try!

Have you check fuel pressure?

Update time.

MAF sensor was totally clean. Checked it and put it back.
No, I haven't checked the fuel pressure, but I am now reminded that I very much want to change the fuel filter as soon as the weather gets a little nicer.
I did an oil change that was way overdue and the car is running much better overall.
While I was changing the oil, I replaced a parking light bulb that had burnt out and also went over the ignition system again.
I removed the metal spark plug boot protectors just in case that was causing any issues (I don't think it was, but they're gone now and it gave me a chance to make sure all the boots were properly connected)
I also noticed that two of my coil packs were loose from when I changed the ICM. This may have been causing some of my problems. I tightened them down and as of today (knock on wood) I haven't noticed any stumbling or anything that feels like a misfire.

I'll update if any problems return.

Thanks everyone, especially Carl for putting me back onto the ignition being the potential source as opposed to my worse case assumption that it was the transmission again.

Namrepus28 wrote:Update time.

MAF sensor was totally clean. Checked it and put it back.
No, I haven't checked the fuel pressure, but I am now reminded that I very much want to change the fuel filter as soon as the weather gets a little nicer.
I did an oil change that was way overdue and the car is running much better overall.
While I was changing the oil, I replaced a parking light bulb that had burnt out and also went over the ignition system again.
I removed the metal spark plug boot protectors just in case that was causing any issues (I don't think it was, but they're gone now and it gave me a chance to make sure all the boots were properly connected)
I also noticed that two of my coil packs were loose from when I changed the ICM. This may have been causing some of my problems. I tightened them down and as of today (knock on wood) I haven't noticed any stumbling or anything that feels like a misfire.

I'll update if any problems return.

Thanks everyone, especially Carl for putting me back onto the ignition being the potential source as opposed to my worse case assumption that it was the transmission again.

Update:

Transmission went out on Monday. Lost all low gears.

Brought it to my trusted mechanic (not who rebuilt it last time) and he has confirmed that there is an insane amount of metal shavings in the transmission housing. Just all over everything.

So the trans is definitely toast. He recommend I not proceed with another re-build based on the cost and find another car.

I'm torn. I'd have to borrow the money either way at the moment, and I was pretty invested in my Bonneville. Then again it costs me a fortune in gas and has other repairs that need to be completed.

Ugh. Life.

Sorry to hear that. Hopefully whatever decision you make ends up paying off for ya.

Also, it is very hard to find a Bonneville type package (comfort, smoothness, etc.). Good luck.

Namrepus28 wrote:

Namrepus28 wrote:Update time.

MAF sensor was totally clean. Checked it and put it back.
No, I haven't checked the fuel pressure, but I am now reminded that I very much want to change the fuel filter as soon as the weather gets a little nicer.
I did an oil change that was way overdue and the car is running much better overall.
While I was changing the oil, I replaced a parking light bulb that had burnt out and also went over the ignition system again.
I removed the metal spark plug boot protectors just in case that was causing any issues (I don't think it was, but they're gone now and it gave me a chance to make sure all the boots were properly connected)
I also noticed that two of my coil packs were loose from when I changed the ICM. This may have been causing some of my problems. I tightened them down and as of today (knock on wood) I haven't noticed any stumbling or anything that feels like a misfire.

I'll update if any problems return.

Thanks everyone, especially Carl for putting me back onto the ignition being the potential source as opposed to my worse case assumption that it was the transmission again.

Update:

Transmission went out on Monday. Lost all low gears.

Brought it to my trusted mechanic (not who rebuilt it last time) and he has confirmed that there is an insane amount of metal shavings in the transmission housing. Just all over everything.

So the trans is definitely toast. He recommend I not proceed with another re-build based on the cost and find another car.

I'm torn. I'd have to borrow the money either way at the moment, and I was pretty invested in my Bonneville. Then again it costs me a fortune in gas and has other repairs that need to be completed.

Ugh. Life.

When I considered replacing the transmission in my '05 Bonneville, I called around a lot to find a place I trusted. The local Chevrolet dealer gave me the best price and best warranty. You may want to consider calling a good GM dealership,. Just my 2 cents.

Wish you the best getting the car repaired. - BC

Another option to consider is a good used transmission.

Archon wrote:Another option to consider is a good used transmission.

Given the longevity of the 4t65 even under babied conditions, I don't think this is the most advisable path. It's too much work to install another question mark.

Was there no warranty on the rebuild? I haven't had to deal with tranny replacement lately so I don't know what the industry standard is for warranty coverage on a rebuild.

As for the track record on the 4T65, yes, we hear all the bad reports of them. But how many were installed over the years? 100s of thousands? Millions? Statistically their track record is probably decent. Worse than Toyota or Ford or...? Maybe. I don't know. But to assume they're all bad may not be justified. There are hundreds of thousands of cars out there with 4T65s that are still cranking along.

Whether or not a used transmission is a good path is up to Superman...I mean Namrepus. It depends on his situation. If he can do the work and pick up a used transmission he could easily be into it less than $1000 and the car may go another 100k miles. Who knows? Maybe he feels is car is not worth another $1000 investment.

I can only speak for myself:

I've had 4 of these cars.
-- 3 of them had hard shifts after long drives (typical line pressure compensation crap) and/or slippage starting at before 100k
-- 1 of them blew the trans at ~165k (busted forward band)

Color me not impressed with the 4t65(or HD). The trans can be built to be a nice unit but from the factory, prior to 04MY, they were flawed at best in my opinion.

188k on mine without any major issues. Granted it's an 03 and I've added a shift kit and trans cooler. I've also been religious about fluid changes and have a nice tune on the car as well.

*shoot* situation for OP one way or another, but depending on the shape of the car and how much work it actually needs, I'd still consider a new rebuild. It's gonna be rough finding another similar car for the price after selling the Bonne.

peter wrote: I've had 4 of these cars.
-- 3 of them had hard shifts after long drives (typical line pressure compensation crap) and/or slippage starting at before 100k
-- 1 of them blew the trans at ~165k (busted forward band)

Color me not impressed with the 4t65(or HD). The trans can be built to be a nice unit but from the factory, prior to 04MY, they were flawed at best in my opinion.

If that were my experience, I'd be unimpressed as well. Mine hasn't given me any issues that weren't self-induced and it has over 175k on it. I did install a shift kit a few years ago.

We've had members have luck with used transmissions. My experience with the transmissions has been similar to Sirius's. Mine had over 150k when I sold the car due to rust, and my friend's has almost 200k. Both did have a shift kit installed, not due to a problem, but to improve shifting times. I do wonder about the quality of the rebuild job that was done. It sounds as if the OP, and his mechanic have enough knowledge between them to decide upon the best course of action.