2001 Silhouette won't shift into 4th - p1811

63vette

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#1
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MAKE:Oldsmobile
MODEL:Silhouette
YEAR:2001
MILES:215,000
ENGINE:3.4L
DESCRIBE ISSUE....I have a customer with an '01 Silhouette (4T65-E) that won't fully shift into 4th gear. It will "hunt" for a few seconds and then drop back into 3rd. The only code is P1811 - maximum adapt and long shift. Naturally, the first thing I did was to drop the pan, change the filter and refill. When that didn't work, I sent him to another shop with a flush machine and had it fully flushed. Still no change. I don't get why a line pressure problem would only affect the 3-4 shift and not any of the others. I'm tempted to replace the 3-4 shift solenoid but don't want to give my customer any false hopes if that doesn't have any chance of fixing the problem. Like I said, the trans seems to perform just fine until it wants to shift into 4th. Thanks in advance for any suggestions.
 
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#2
starting simple easy first-
are they towing*, any other codes, did you check freeze frame data?
with scanner look
at shift times, -0.65 seconds...
Line pressure check...

hail mary: with new fluid and filter use scanner to clear TAPS - the PCM has frozen adapts when DTC set

then you are up to internal trans issue.

*possible overloading, exceeding the trailer towing limit or towing in overdrive
 

nickb2

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#3
Are you sure you have the right code?

I am not seeing P1811 - maximum adapt and long shift.

My alldata jumps from P1189 to P1336

Normally a P1811 should be accompanied by a P0742 or a P0748.

I did google a bit, found this.



See pdf attatched, and yes, the pcm freezes the shift adapt.

If 3 hold, the band is probably fine.

if this is your problem.
 

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nickb2

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#7
Now I feel like an idiot, I may need glasses, P1811 was there all along. Disregard post #3 but read the TSB. It may help with the flow chart I provided.

Thats what happens when I respond to 3 ppl at once, I get mixed up.;):beer::bat:
 

63vette

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#8
Thanks so much kev2 & nickb2!
@kev2: no towing - with the current owner anyway. Originally (almost 4 months ago), there were other codes but only 1 that should affect this issue - P0748. That code, as well as all of the others except P1189 (eng oil press crkt), has not reappeared since. I did look at the shift times for the the gear changes and the 3-4 shift did exceed the .060 or .065 parameter.
I will probably be able to get the van in tomorrow and see if I can clear the TAPS. Apparently, clearing the P codes doesn't clear the TAPS. My scan tool is Autoenginuity PC software with extended Domestic and Japanese coverage.

@nickb2: no worries about missing the P1811. You were right about another code accompanying the P1811. As you can see from above, it did originally generate a P0748 but it has not been set since. I feel like the dumb ass since I missed the TSB. I swear I looked at the TSB history and somehow missed that one! Thanks for the catch and the flow chart!

I still can't help but wonder why a pressure issue would only affect the 3-4 shift but...stranger things have happened! I hope that clearing the TAPS and/or replacing the pressure control solenoid will solve their problem. I'll check but seriously doubt that my scan tool software will allow me to command the solenoid to test the actual pressures as described in the TSB.

Thank you both again...BAT is the bomb because of outstanding members like the two of you!
BTW, I will follow up with the results when I know the outcome!
 
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#9
I think a hail mary for this may be R&R PCS, hoping BP042665 knows a trick ...
 

billr

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#10
Bobby P, if the OP removes the pan and VB, is there an air-check that can show if one of the clutches has obviously bad seals?

How about attaching a gauge for LP (with long hose) and driving to observe what "commanded LP" is relative to what is actually seen on the gauge?
 

bp042665

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#11
ok i have fixed many of these . the 4th gear hub is stripped on the end and when 4th gear is commanded is will not stop because its stripped and the computer is detecting a long shift apply and will set the code 1811 also go full line pressure. i will replace the hub update channel plate and updated valve body. With the high miles it probably need to be overhauled . just saying
 
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#12
I am such an optimist :)
NO not even a quarter million miles and we need to tear into it!!
come on BP there must be a option.... what I call a hail Mary maybe a whole bottle of trans in a can ?
 
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#14
you know I am just kidding... I hate to give up

Could high line pressure left un corrected lead to the failed hub issue?
 

63vette

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#15
Well, I had this van back on Friday morning. My Autoenginuity did show the TAP values along with many other values. Also, I was able to clear the stored values and start fresh. As expected, the P1811 had been set again so I cleared that, too. The long and the short of it is that the electronics appear to be working correctly in that it shows that it is shifting into 4th BUT the RPM/MPH don't change with the indicated shift into 4th. It was later that I saw BP's post which confirms that the problem can only be corrected by replacing internal components.

Thank you, BP, for crushing my hope for a fix that doesn't involve disassembling the trans! kev2, we're of like minds...exhaust every possible option before resigning ourselves to the fact that it requires much more serious repair/rebuild treatment. I suspect that the customer is not going to want to spend the money on an extensive repair and will probably trade it off!

Thanks again for all of the responses!