Transmission won't shift 2-3!!! - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 11-06-2006, 01:51 PM   #1
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Default Transmission won't shift 2-3!!!

I've got an interesting problem with my 2001 Buick LeSabre. It'* got the base L36 V6 plus 4T65E transmission, with 89,000 miles on the powertrain. I bought this car about two months ago, and I noticed that when I depressed the accelerator about 1/2 way at 75 MPH it appeared that the transmission shifted down too many gears, as the revs were way too high for what I would expect to be a 3rd gear downshift at that speed. ALso, I noticed that in town, it appeared to shift too late from second to third gear (revs too high).

I took the vehicle into the dealer for a look, and they said that the transmission is not shifting into third gear AT ALL (upshift or downshift). It was going directly from 2-4 and vice versa. The dealer'* solution was a brand new transmission (of course) at $2900!

I've got a vehicle scan tool software package on my laptop [car code OBD-II], so I connected and went for a drive, below are the results:

* When I place the shifter in D2, and manually upshift to D3 nothing happens.

* Looking at the transmission status information there are no faults or problems (detected) with any of the shift solenoids, TCC solenoids, shift pressures, etc...

* The vehicle computer appears to be attempting to command the transmission to go to the correct gear: When I manually move the gear selector from D2 to D3, the proper solenoids appear to activate to cause the transmission to shift from 2 to 3. The same holds true for D4 to D3 manual commands.

* The feedback of what gear the transmission is currently in (manual commands or in Automatic) appears to be the correct one selected (meaning the feedback indicates that D3 is engaged when it should be, but it is really in D2).

* There are no fault codes or anything unusual that can be picked up using the standard OBD-II GM interface.

It appears that whatever the mechanism that causes the transmission to shift, and the feedback of what gear the transmission is really in appears to work. But the actual shifting does not take place.

Has anybody experienced anything like this? Is it true that it'* rebuild time? What are my options, or things I can check before taking the plunge for a new tranny?

All thoughts are appreciated!
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Old 11-06-2006, 01:55 PM   #2
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2-3 shift solenoid, third gear clutches, 3rd gear sprag or the valve body are all possible culprits.

You need to get a scanner that can scan tranny codes.
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Old 11-06-2006, 02:00 PM   #3
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Quote:
Originally Posted by Rogue
2-3 shift solenoid, third gear clutches, 3rd gear sprag or the valve body are all possible culprits.

You need to get a scanner that can scan tranny codes.
Where can he get all those things and at what approximate cost? Intense?
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Old 11-06-2006, 02:16 PM   #4
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Quote:
Originally Posted by lash
Quote:
Originally Posted by Rogue
2-3 shift solenoid, third gear clutches, 3rd gear sprag or the valve body are all possible culprits.

You need to get a scanner that can scan tranny codes.
Where can he get all those things and at what approximate cost? Intense?
Depends on whats wrong, we carry everything for the 4t65e on our site and all the prices are listed. Really hard to diag a transaxle over the internet
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Old 11-06-2006, 02:53 PM   #5
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Lol! I know you probably can't diagnose this from here. I really asked more to get him closer to an answer to his original questions.

The cost question was more to see what cost he would incur if he bought replacements for all the parts you listed, sort of like an overkill, to see how that cost compared to a new transmission from the dealer.
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Old 11-06-2006, 02:58 PM   #6
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Something to try is to buy a can of Seafoam Trans Tune, and see if that frees things up. I've had some luck using that to free up some sticking parts. I think it costs around $5 - $6 for a can at virtually any auto parts store.
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Old 11-07-2006, 08:44 AM   #7
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If we were talking about a Turbo 400, I'd say you need a new vacuum modulator. But since we're talking about a 4T65E, I don't know what to say. What takes the place of the vacuum modulator in these modern transmissions Archon?
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Old 11-07-2006, 08:49 AM   #8
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Quote:
Originally Posted by MACDRIVE
If we were talking about a Turbo 400, I'd say you need a new vacuum modulator. But since we're talking about a 4T65E, I don't know what to say. What takes the place of the vacuum modulator in these modern transmissions Archon?
Electronic shift solenoids
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Old 11-07-2006, 08:58 AM   #9
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Quote:
Originally Posted by BillBoost37
Quote:
Originally Posted by MACDRIVE
If we were talking about a Turbo 400, I'd say you need a new vacuum modulator. But since we're talking about a 4T65E, I don't know what to say. What takes the place of the vacuum modulator in these modern transmissions Archon?
Electronic shift solenoids
Ahh....yes.... there we go.
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Old 11-07-2006, 06:02 PM   #10
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interesting. What are your RPM'* on the highway at, say, 65 MPH? A WOT downshift at around 65 will make the car downshift into 2nd gear and at 65 MPH 2nd gear is about 4,500 RPM I'd guess. Your car in OD at 65 should be right near 2,000 RPM. (a bit lower)
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