Tranny Problems??? 98Riviera!!

Soo I was doing some pulls with my other fellow 3.8 friends and during one pull, when my car was about to shift out of 3rd gear my Rpms stayed high for about a second before a shift. A raced my friend with a regal moments after and this time my rpms bounced for a second before they shifted. I did check my tranny fluid which seems to be a little low but not sure if that's the real problem, thanks for the help , new at this 3.8 stuff, my car also reads a P0420 code, any ideas?

It could be your ATF got all bubbled up after several enthusiastic pulls.
Code P0420 is about the low efficiency of catalytic converter.

Is the transmission stock and are all the shift points and pressures stock settings in the powertrain control module? .if it's all stock it's a good chance it's going to need repairs soon. There's nothing you can do really other than replace the fluid and filter for maintenance. If the trans if flaring between shifts it could be a worn clutches. If it's an all of the sudden occurrence it could be debris floating around in the transmission ( think metal filings usually) . These are cars built for comfort not high performance so each shift is timed generally at .750 sec for smooth comfort but it's not meant for a performance shift. This 4t65E is basically a heavy duty electronic version of a 4t60E in a car that could have used a more robust 4t80E transaxle . Anyhow, because the shifts are timed as such the line pressure is increased, as throttle position, torque and road speed are increased simultaneously and shift points are moved to higher rpm as well..its all on tables written within the programming of the PCM ....So run hard and shifts ate commanded quicker and with more line pressure. So if you have a clutch issue in a pack or sh!t caught in the fluid flow...it may cause a flair during a shift generally speaking.(see diagnostic pages below) ...I have altered all my transmission shift points, line pressures, shift speeds (.250 sec) as well as torque converter operation and removed all speed governors using HP Tuners software. I altered it 5 times until I had it set just right. It was a learning experience. My trans shifts crisp and clean, releases the TCC under less throttle, downshifts quicker and holds third gear up to 43 mph under normal throttle ..this makes the car feel allot less sluggish and accelerating quicker under light to moderate throttle also it will shift to 4th gear at 125 mph under full throttle . Only brave enough to try it twice!

Keep in mind that the shifts are all timed and controlled via solenoid pack in the side case. Here are some diagnostic charts and diagrams to help out ...

Troubleshooting

Did you find any problems?

Angeles98 wrote:

Soo I was doing some pulls with my other fellow 3.8 friends and during one pull, when my car was about to shift out of 3rd gear my Rpms stayed high for about a second before a shift. A raced my friend with a regal moments after and this time my rpms bounced for a second before they shifted. I did check my tranny fluid which seems to be a little low but not sure if that's  the real problem, thanks for the help , new at this 3.8 stuff, my car also reads a P0420 code, any ideas?

What's the general state of maintenance of your car?

An ignition system misfire or any other fuel control system malfunction, that causes the fuel injection computer to inject excess fuel (due to a loss of fuel trim control), will cause the catalytic converter to overheat and eventually malfunction and set a P0420 DTC.  The malfunction can be clogging or non-performance.  If you have no symptoms other than rotten egg smell and sucky gas mileage, you have non-performance failure tripping P0420.  If you have lack of power, hesitation, maybe rough idle, then you have clogging and your combustion is off stoich as a result, so you set the code.

Horsing the car repeatedly while also having a marginal MAF, or a slightly leaking LIM gasket (antifreeze in the exhaust) will do it (set the P0420).

Engine additives (esp. oil additives) containing very high Zinc could, I imagine, poison your cat over time, which is one reason *not* to use diesel oil in your gas powered car unless you know for sure what is in the additive pack. It's not much of a 'thing' if your rings and valve stem seals are good.  It's a headache if your rings are worn and therefore you are burning oil.  I can't tell from here.

If your sensors are lying to the PCM and your car is running rich, your cat will overheat and fail, which will set the P0420 (for instance a marginal MAf or poisoned upper oxy sensor would do this, or set a P0171, depending on what else is wrong).

In general you ought to figure out if your car is running wrong due to misfire, leaking or (partly) plugged fuel injectors, retarded spark timing or weak spark, or if it has  high engine oil or coolant consumption.  Figure that out, fix it, then depending on how good the fix is you still may need to replace the cat.  Your PCM will retard the spark timing if you have a supercharger and are burning regular instead of premium gas and nothing else is wrong.   In that event I imagine Regular combined with hard pulls can get you P0420.  You can get a slight misfire on an SC car by replacing one or more of the coils with coils intended for the NA car. They will work but they don't flash as hard as the SC coils so you get a mini misfire or chuggle that you can *barely* hear and never sets a code.

The insight here is that catalytic converters don't die, they are murdered by abuse or slaughtered by neglect.  Bottom line is what to do depends a lot on the general state of maintenance of your car.

Albertj

The bottom line is the transmissions in these cars are the weak link. The 98 has the 4T65HD I believe, and it is a good transmission, but if you make a habit out of racing the car and spinning the tires, you will hurt it, eventually. I currently have 197,000 miles on my original transmission and it shifts mint. I change the fluid every 20,000 miles with Dex 6 and I do not abuse the car. You don't have to step on these cars very much to make them go.

The P0420 code is just the rear O2 sensor telling the PCM that the catalytic converter isn't up to snuff. Want to try something cheap? Get an O2 extender for the rear sensor, like this one,

https://www.amazon.com/Stainless-Oxygen-Sensor-Spacer-Expender/dp/B07WRYDPGB/ref=sr_1_1_sspa?keywords=o2%2Bsensor%2Bextender&qid=1577544406&s=automotive&sr=1-1-spons&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUFWMlpDV1VVVTQ2VzkmZW5jcnlwdGVkSWQ9QTA3MDc2NzROUjJJNTkxWDhTSTkmZW5jcnlwdGVkQWRJZD1BMDk5NDg0ODFQVlI2TTVDNThGRU8md2lkZ2V0TmFtZT1zcF9hdGYmYWN0aW9uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl&th=1

Google "P0420 fix", or put it into Youtube. What it does is give that rear sensor less of a sample and that does the trick.

Did you solve the issue and what did it take?