Transmission jolt or possible slippage

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Boj

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I’ve owned this 2004 Regal LS for about a year and have put about 20k on it so far leaving it at 125k right now. Only have had like one or two issues with it so far one of which is the transmission.

Every day issue: if I slow down enough for it to be in the first gear speed range, so 1-10ish mph, then hit the gas again it will jolt hard like it wasn’t in gear then suddenly engaging first. Only way to get around this is for me to give it the tiniest amount of throttle at first but you can still feel it. Think of the speed like when you take a right at a green light or pull into a parking lot.

Occasional issue: sometimes, usually when the engine is still cold, accelerating from a dead stop will cause a rise in rpm then a jolt into first gear. Only happens once then not again for several weeks or months.
 

Zeroboostbuick

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2018 Regal Sportback - 2010 Yamaha R6 (track bike) Past cars: 92 LeSabre, 98 Regal, 02 GrandPrixGT
Check the level and/or change the transmission fluid with either AMSOIL ATF or Mobil-1 ATF.

To check tranaxle fluid level:

Go for a 5 to 10 minute drive...
Park on level ground... Put the gear shift lever through all the different gears (P-N-D-3-2-1) leaving it in each gear for 3 to 5 seconds... Then go back to park...
Let car idle for 1 or 2 minutes..
While car is idling, take the trans dipstick out and wipe it... Then proceed to check the level (while car still running).

If the fluid smells a little burnt or is not a nice red/pink color, it means it's bad and needs a change.

The only other ATF besides AMSOIL and Mobil-1 I would consider is the stuff GM sells.

I also recommend adding some Lucas Transmission FIX.

If this doesn't fix the problem then the pressure control solenoid need changing.
 
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Boj

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Didn't do the shift through all the gears part but I checked the fluid a few weeks ago and it's perfectly pink, right on the line, and smells good still. Had a burnt out power steering pump in my old Wagoneer so I know that god awful smell haha. I need to change my motor oil pretty soon so I'll try changing the transmission fluid while I'm at it. New filter as well of course.

Speaking of my old Wagoneer, it has a transmission linkage going to the carburetor much like Fords have that depending how much tension you put on it changes the shift points. Too little pressure and it goes into 3rd immediately but too much and it'll never shift out of 1st. Is the pressure control solenoid the same thing here but electronic?
 
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Zeroboostbuick

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2018 Regal Sportback - 2010 Yamaha R6 (track bike) Past cars: 92 LeSabre, 98 Regal, 02 GrandPrixGT
Didn't do the shift through all the gears part but I checked the fluid a few weeks ago and it's perfectly pink, right on the line, and smells good still. Had a burnt out power steering pump in my old Wagoneer so I know that god awful smell haha. I need to change my motor oil pretty soon so I'll try changing the transmission fluid while I'm at it. New filter as well of course.

Speaking of my old Wagoneer, it has a transmission linkage going to the carburetor much like Fords have that depending how much tension you put on it changes the shift points. Too little pressure and it goes into 3rd immediately but too much and it'll never shift out of 1st. Is the pressure control solenoid the same thing here but electronic?
Pressure control solenoid works like hydraulic actuators allowing fluid one way or another.
If it slams into gear only if the trans fluid is hot or cold you could try to remedy it with premium ATF fluid and some Lucas transmission fix. But if it does it all the time then one of the solenoids is going bad. Never had to change one myself but I assume it shouldn't be more than a few hundred beans.
Your ECM might have some codes stored and they could point in the right direction.
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Boj

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Most stuff seems to be fairly easy to service on these 4T65-e’s but from what I’ve read and watched so far the PCS is behind the side cover of the transmission so it’s a pretty tough job for a home garage mechanic to get at. Plus I guess you need to program the replacement and I don’t have a GM compatible scan tool to do that so let’s hope the fluid change does the trick.

Thanks for your help.

Edit: I do need to find a new scanner that can read GM systems though. Mine is just a $20 harbor freight model for reading basic OBDII codes. Can’t get stuff like abs, tcs, airbags, or OEM specific codes on this thing.
 
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Boj

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Haven't gotten around to changing the fluid yet but I just noticed something else odd while driving around today. Hit the gas kind of hard to pass someone at slow speeds and when it downshifted into first it revved to about 3800 rpm then just didn't go any higher. It felt like it was banging against the park rev limiter and didn't shift into second until I left off the gas. Super scary at the time so I babied it back to near my house and tested it a bit more. Each time rolling into the gas hard from a stop it hits near that same rpm then just quits. Put it manually into first however and it goes past that rpm just fine.

I never really drive this car very hard and especially not hard enough to trigger a downshift into first all that often. Other gears can rev higher to my knowledge.
 
986
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S.W. Ontario Canada
Buick Ownership
2018 Regal Sportback - 2010 Yamaha R6 (track bike) Past cars: 92 LeSabre, 98 Regal, 02 GrandPrixGT
If it doesn't want to go beyond 3,800 RPM maybe your problems is not the transmission ??? or you have 2 separate problems.

If you can manually shift from 1st to 2nd to 3rd with the floor shifter, then at least you can get around that way for now till you figure it out and get it fixed.
 
Thread starter #8

Boj

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No it shifts and drives fine it's just under hard throttle in first gear that it does that. For example:

In drive > light-moderate throttle > shifts through 1-2-3-OD to cruising speed

Manually in 1st on floor shifter > any amount of throttle > drives and revs until it hits redline

In drive > hard throttle > drives and revs to 4000ish then doesn't rev any higher > let off throttle and it shifts into 2nd > shifts through 2-3-OD to cruising speed
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HotZ28

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You evidently have a sticking shift solenoid, or a valve body problem. When was the last time the fluid & filter were changed?
 
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