Hello everyone I have a confusing question that I hope it can be answered, My 1997 Buick Lesabre transmission slips at random when I shift into overdrive. I have my mechanics look at the transmission and have them drive the car to recreate the problem and what do you know the car doesn’t do it. I made a post about this problem a while back and it wasn’t the A/C that was the problem. I do not drive fast in the car and I checked the Transmission dipstick and the fluid is still red and at the full mark. I brought my car to Auto zone to check the codes but all i get is a loose gas cap. Please and thank you again.
transmission slips at random when I shift into overdrive
Does this mean that you are actually shifting to overdrive ? If so what happens when you place it in drive and just let the transmission do it’s thing.
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@VOLVO_V70 Yes When I shift it into overdrive and let it do its thing it does not engage and then the car feels like its in third. When I’m at a stop light I have to shift it from park to overdrive and then it kicks in but when Im at a full stop again the car does not want to engage overdrive and it feels like I’m trying to calm a bucking bronco.
sorry i forgot to mention i do not have a OD switch where i can turn it on and off
One last thing then I am going to finish my coffee. You should not be placing the car in park at stop lights. Waiting for long trains yes. I just don’t follow the shift into overdrive you are talking about. Do you not just put the lever in the position where it is “D”. The transmission will shift the gears as needed and you should not have to do anything.
I apologize Mr. Volvo and thank you for the word of advice and also i apologize for not explaining myself clearly ._. . I shift the lever to Drive the transmission shifts to first gear but roughly hard which jolts the car after that it does not want to shift at all and then it slips and will not go gradually
And I apologize i forgot to mention when it shifts roughly i hear a grinding noise coming from the transmission as well
I think this transmission is the four speed. It would have a drive “D” position that would shift it through 1-2-3 gears but stay in 3rd which would be like the normal high gear. Then it has the “OD” position that when selected would either go to 4th from 3rd or run it though the gears from a stop 1-2-3-4. 4th gear has a separate clutch but it is not very substantial I’m told so don’t want to use it except in easy straight and level flight or you’ll burn the clutch out.
At any rate, slipping, banging, grinding, just means that it is time for a full overhaul to replace the clutches, torque converter, and other damaged parts. I’ve never had a transmission that slipped or made a grinding noise that did not require a full overhaul, so its to the trans shop I’m afraid. IMHO.
Have you tried just driving it in “3”, if it has the 1-2-3-D gearshift, and if so, how does it perform?
Are you still having the vent/defrost blend issue as in your previous post?
Is the engine racing/revving/running too fast?
Is there a reason you were putting it in Park at stoplights?
I’m wondering about a vacuum leak.
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If the information I found is correct this vehicle has : P-R-D-3-2-1. The D has a circle around it that only means it will shift and at the correct time it will put the transmission in Overdrive automatically. I guess that means that the transmission is acting up with the selector in D, the part about putting the car in overdrive was confusing. Why the mechanic who drove it said it was fine is a mystery.
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A transmission shop should be able to measure the transmission fluid pressure. That’s probably the place to start. You might do a proper service, see if that helps too. Drain and refill and service the filter if applicable. Make sure the proper fluid is used. If there’s any possibility the wrong fluid was ever used in the past, you may have to do several drain and re-fills. One indication of this would be that the first drain and re-fill helps, but doesn’t solve the problem.
My guess though, if this is the original transmission, you will be getting it rebuilt or a replacement transmission very soon.
The “D” with the “O” around it is the overdrive setting or 4th gear if its a 4 speed. I think that was pretty standard. The 3rd gear is the same as normal high gear. I just don’t remember if they ever had a three speed with a separate overdrive gear. Don’t think so. When the went to the D with the O around it, I believe it was the 4 speed with 4th as the overdrive gear with the weak clutch.
Hello all thank you for responding I apologize for not getting back due to matthew knocking out the power, and thank you for responding. @VOLVO_V70 my car does not have the optional button to turn overdrive off its P R N OD 3 2 1, that what i was trying to explain when shifted to OD the car engages but then it downshift hard and then it doesn’t want to engage into OD again.
@OldcarsRbest when i place it in third i still have the blend issue with the A/C on and now when i don’t have the A/C on it does it again where i can hear it clear as day open then making a noise then shutting again. The reason why I put it in park at the stop lights was if i shift out of OD into either 3 or park and then shift it back to OD it engages back normally. What I also noticed is when the A/C is on and i put it on the Recycle feature the car is back into OD and the problem never occurs again until i shut off the A/C and then it starts back struggling… Also the problem happens if i dont have the A/C on and the windows open when i come to a full stop at a red light and try driving again the car is struggling to shift normally so what i do is i put my foot on the gas not as hard. I got 10 mph i take my foot off for a bit then put my foot on the gas then let it off a bit and do it again and it engages OD again. And If its a possible vaccum leak how can i check for it?
@GeorgeSanJose yes this is the original transmission in the car and this problem never happen before till now. It baffles me. But when I bring it to the mechanics I told them what was going on with the car transmission and to see if they could recreate the problem that I was having. They drove it with the A/C off and the car did not show the problems I was having and I was with them in the car. They turned the A/C on and the problem still did not show. I also brought it to a Transmission shop to have them measure the transmission fluid pressure and each time it comes back normal.
@bing That what I thought so if the transmission was going bad but I believe the grinding noise was coming from somewhere else, Its just when the A/C is off or on the blend doors like i explained in my previous post and also to answer the question to @OldcarsRbest.
My family also believes that nothing is wrong and everything is fine with the car and they tell me i worry but I know for sure driving this car everyday I know something is wrong.
OK, you have the four speed then. Regular D will let it shift 1-2-3. It won’t go into 4th until you shift it to the OD position. You don’t have overdrive in 1-2-3. 4th is the OD gear. Sure you aren’t talking about the lock-up torque converter? That’ll lock up at around 40 mph or so in the other gears.
I have no idea why the AC should have any affect at all but the trans will have some electronics to it. So the best thing to do right now before it gets worse is get it to a trans shop for an evaluation. They can check the symptoms, pressures, check for any trans codes, the converter operation, and the shift solenoids. Might just be the solenoids but might as well find out. If it is something simple you can maybe avoid major work by catching it early. But a good trans shop, not AAMCO or one of those but an ATRA member shop.
Too bad transman isn’t around anymore. He was the resident transmission expert. My info is only based on personal experience. Must have had about ten overhauls.
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Just a guess, but turning on the AC compressor gives an extra mechanical load to the engine, and engine load is one input to the transmission’s computer. That’s the computer which decides what gear to use for a given driving situation. So it may be normal for some interaction between the transmission and the AC. And for a failing transmission, the effect may be greater.
Automatic transmission have clutches, just like manual transmissions, and those clutches wear out w/use. Usually when that happens the transmission computer will increase the transmission fluid pressure enough to compensate. Until it has reached the pressure limit. Since your mechanics say the pressure they measure is normal, and therefor less than the limit, that would indicate your transmission clutches remain w/in their wear limit. This assumes the pressure test was done correctly.
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