Odd shifting issue

[dan]

hello everyone, this may get lengthy… so hang on tight, i have asked tons of people what may be wrong and i can get no definitive answer

I own a 1998 Buick Regal LS 25th anniversary edition, it has a 4T65E Transmission and the 3800 Series II L-36 N/A engine… it has 202,200+ miles and still runs like a clock, its transmission has been replaced some time in its life time with either a junk yard unit or rebuilt as paint marker lettering adorns parts of the transmission.

the transmission shifts great, nice and smooth and confident into every single gear up and down until the engine reaches around Operational temperature and what appears the PCM goes into a closed loop operation… after that funny things can happen, funny things like this.

quite commonly it does this after long cruises at highway or freeway speeds but sometimes it does it in city stop and go traffic but rarely and rarely does it in repetitive succession, it is very intermittent, first what happens is before i come too a stop the transmission feels like it down shifts into its lowest gear with a clunk, as if its down shifted manually rather than coasting it almost “Engine brakes.” it can do this so hard at some times it feels like the whole car jolts, or so soft sometimes you can barley even feel it or not feel it at all!
then once you accelerate the car accelerates just fine no slippage all the way through first gear, then when it should shift, it does not and holds first until about 3,000RPM like its being held in first gear, then it either shifts normally into the next gear, or more commonly, the engine suddenly revs another 1K RPM as if the transmission shifts into neutral, not like slippage! then the transmission smoothly shifts into second gear without slippage, and goes through the rest of the gears without issue… smooth as glass, sometimes right after the event if i come too a stop at another stop light or something it will do it again, but rarely… after the event especially in the case of city driving the transmission usually shifts slightly hard from first too second gear with slow moderate acceleration but i have noticed if you want too pick up the pace a little more peppy it does not shift so hard..

in scary cases i have had issues where i am going down the highway 55… having too slow down too 45 for a Semi, then when i want too get around him quickly, i press the gas, the engine adds more power, however the transmission does not down shift from the next lowest gear, commonly second gear, i will press harder and harder on the accelerator too pick up some pace, then the transmission seems too shift into neutral and the engine revs dangerously high once according too my Tacho it revved too 6,000RPM when it seemed too shift into neutral, it will either then shift into second gear, or until i let off the gas beacuse i don’t want a rod through my block, and it just goes back in third.

I have no engine light or codes pertaining too the transmission, i have replaced the TPS, and the MAP sensor, changed the trans fluid and filter and put Lucas trans additive in it and cleaned my MAF sensor, and currently swapped engines beacuse the engine that was originally in the car was neglected… and im guessing coolant got into the crank case and it ate the main and rod bearings and it threw a rod bearing eventually, or that dangerous 6K rev with my trans may have done a rod in… who knows.

also i have tried shifting through the gears manually, it doesn’t work that way either, once i manually selected second gear at about 35-40MPH being carful not too add to much accelerator, usually at this time the engine is doing 3,500 4,000RPM when i pressed the gas the engine would rev like it was shifted into neutral rather than 2nd gear, but when you let off the gas it would shift back into second, it would do this for a little bit, then when you shifted into second manually with the gear selector, then it would go into second…

any suggestions would be appreciated, thanks 🙂

Topic

[celticbhoy]

When was the last time the transmission fluid was changed? What’s the fluid level like and does it look/smell burnt? Check the level with the car running and when it’s at operating temperature.

[dan]

I forgot too add, when i changed the fluid which was really no more than 10,000 miles ago, it was only in need of changing just a slightly darker color… it was not burnt, wasn’t black did’t smell funny, and there was hardly any particulates in the pan, the tranny fluid now is at a almost perfect level, just right, and its a nice pink color and smells just like it should… which further supports my theory its of some sort of strange electrical issue and the trans is not slipping.

thanks for reminding me too add that 🙂

[college man]

From what I read.GM had a problem with the PCS pressure control solenoid.

http://www.gminsidenews.com/forums/f53/shudder-hesitation-takeoff-1998-riviera-83086/

[Matthew]

Do you have any bog down? Does it seem as if the car always has it brakes applied? I got a simular issue my car will not shift out of 1st until it hits 40mph second i let off the gas car slows at a steady pace like i am using the ebrake.

[dan]

thank you for your post! i did not know the pressure control solenoid could cause that many issues, however it never seems to go into a long shift adapt mode, nor do i ever get a P1811 code on my PCM for my transmission, maybe there is a ray of hope after all…

however could this be bad and not set any codes at all?

thanks again.

[dan]

[quote=”LeoTheLion89″ post=57803]Do you have any bog down? Does it seem as if the car always has it brakes applied? I got a simular issue my car will not shift out of 1st until it hits 40mph second i let off the gas car slows at a steady pace like i am using the ebrake.[/quote]

nope, it does not seem to bog, plenty of power, just neglects too shift till about 3,000 RPM or seems to go into neutral between first and second gear.

[college man]

The code may or may not set. 🙂

[dan]

[quote=”college man” post=57841]The code may or may not set. :)[/quote]

thanks a lot, you and this website are the first too finally give me an answer that makes sense… the Pressure Control Solenoid typically fails when the engine reaches operational temperature, and if it does fail then how can it regulate pressures correctly too operate the transmission! now that i know what it probably is, i can finally take the next step and figure out how to get it fixed!

[college man]

Happy to help. Keep us posted on your progress. 🙂

[Author]

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