Torque converter speed ratio behavior

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Cannon762

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Chasing a light shudder coming into 3rd gear WOT, talked to my tuner who thinks my TC may be on it's way out based off of torque converter speed ratio (on 3rd gear shift, speed ratio drops to mid 80's before somewhat sluggishly coming back). Car has 38k, fresh fluid drain/fill (doing another soon as well)

Was curious if anyone else monitors their tc speed ratio and how it behaves. Even under normal acceleration and cruising it drops down to the low/mid 80's into 3rd gear and obviously lower at slower speeds. Highway speeds it's between .98-1.0

One mechanic has gone on a ride along and said he's not even sure it's TC, he said he felt it at 60ish mph regardless of gear, which makes him think it could be wheel balance/pressure since the wheels and tires are new.

If anyone has any logs they could look at, or just throw their TC speed ratio up on their LiveWire or similar and do some driving around, I'd appreciate the comparison.

Thanks all
 

FiveLeeter918

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Snap24 is a 35-90 hit, Snap25 is a 0-90 pull, Snap26 is a cruising log over the period of about 2 minutes. Snap27 is just a zoom in of the period that is not static at 1.00. Mostly during the light acceleration.
 

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Cannon762

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I had the same issue on the 1-2 and 2-3 shift, and people recommended an extra quart of trans fluid. It worked for me. You might want to start with that one. Easy is good. :)

I put an extra half quart in and it did seem to eliminate the shudder on one pull, and drastically reduce it the next. On my next drain and fill I'll keep it a little fuller and see what happens there.

Snap24 is a 35-90 hit, Snap25 is a 0-90 pull, Snap26 is a cruising log over the period of about 2 minutes. Snap27 is just a zoom in of the period that is not static at 1.00. Mostly during the light acceleration.

Very helpful, thank you so much for taking the time. It looks like yours never approaches dropping below 90 really too often under pulls. Here's the area where my tuner was concerned about and mentioned it could be that my TC is on it's way out - this was a 0-100 pull. It looks like the lowest value here is .92, however on another log with a 0-100 pull it was down at .88 I believe. In your opinion does this look suspect? I don't know that it matters but I do use upgraded trans mounts.
 

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Cannon762

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Small update in case anyone finds this thread in the future and needs it. I did a full drain/fill and drained 5.6 quarts, which was already dirty looking despite a drain and fill recently.

Replaced exactly as much as I took out, let the trans warm up a bit and did a pull and the 3rd gear shudder is gone. I'll do another drain fill again relatively soon, on sm105ks advice.

As far as converter speed ratio, mine just seems to dip like that in 3rd gear. 3rd drops as low as .85 but 4th and 5th maybe tick down to 94-95 regardless of throttle. Ill keep an eye on that but if it's not shuddering I'm not going to lose sleep about it.
 

SM105K

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Small update in case anyone finds this thread in the future and needs it. I did a full drain/fill and drained 5.6 quarts, which was already dirty looking despite a drain and fill recently.

Replaced exactly as much as I took out, let the trans warm up a bit and did a pull and the 3rd gear shudder is gone. I'll do another drain fill again relatively soon, on sm105ks advice.

As far as converter speed ratio, mine just seems to dip like that in 3rd gear. 3rd drops as low as .85 but 4th and 5th maybe tick down to 94-95 regardless of throttle. Ill keep an eye on that but if it's not shuddering I'm not going to lose sleep about it.

Yeah. The 6f55 trans do not like dirty fluid. When you told me that the fluid was looking dirty even after a drain and fill it got me thinking.

Personally I would buy a case of Mercon LV from Amazon. I would drive 100 miles on your current fluid and drop it, fill it again. Drive another 100 miles and do it one more time. Most of the old fluid will be gone, and that should make the trans happy.
 
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FiveLeeter918

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great to hear the update!

as for the logs, that stumble is a little curious, but if it doesn't affect drivability just keep it in the back of your mind should anything else pop up.
 

krewat

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As far as converter speed ratio, mine just seems to dip like that in 3rd gear. 3rd drops as low as .85 but 4th and 5th maybe tick down to 94-95 regardless of throttle. Ill keep an eye on that but if it's not shuddering I'm not going to lose sleep about it.

I am no expert, but that sounds like typical lock-up behavior for the TC. They might modulate the lock-up clutch a lot more in the lower gears, as any lock/unlock is going to be felt a lot more because of the gear ratio. Ford and apparently at least a few others (my friend's 2017 camaro comes to mind) are still not quite getting the modulation of the lock-up torque converter just right. Also, I wonder what the ratio spread is between 3rd and 4th or 2nd and 3rd... maybe that's got something to do with it.
 

Johnbigdog

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The ratio doesn't mean much if you don't know what the p.c.m. is commanding. shift. Could be in lock or fluid coupling and you wouldn't know.

Your best bet is to look at the PIDs TCSLIP-DSD (the commanded converter slip) and TCSLIP-ACT (the measured ram difference between the engine and turbine shaft)

When tcslip-dsd reads 1020 thats a full off command. Any slip or lock is acceptable. When it reads 0 thats full lock up and should follow within 10-15 rpm. For example if the desired is 10 rpm and actual is reading 50 for the time you feel the shudder, thats a slip.
 

ticoscen

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2010 PP SHO with shudder. It finally threw a P0741 code too the other day. TC clutch solenoid problems and a failure to lock on a highway speed test. I cleared the code and it didn't come back but still shudders. Takes a lot of fixed gear acceleration tests to get the code to show and is the only time I've seen the code. Changed tranny fluid and added a tube of anti shudder. Didn't go away. Third gear pulls from 15mph to 50mph, you can really feel it. BTW, Endurance Autorepair insurance sucks a big one. They denied the claim saying that 128,000 mile TC failure is "normal wear and tear". Well, all failures are due to normal wear and tear, eh? I cancelled the contract and am getting most of my money back. Just glad I figured out their claim denial game early in the contract from this test. Will use my prorated refund to get the tranny shop to change the TC to an new upgraded TC and flush the tranny out of the 6F50. Live and learn. Normal wear and tear.... sheesh.
 

2013SHOpp

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i see desired slip at 1020 but actual will be at 3-500. Is that normal. i threw a p016b code and the only thing that i can think of is tc.
 

Johnbigdog

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The pid: Tc slip dsd when it reads 1020 is a default "off" number. This is what the pcm wants. Tc-slip-act is the difference between engine rpm and turbine shaft speed.

When tc-slip-dsd reads something other than 1020 you want to see a tc-slip-act within 10-15 rpm within a few seconds.
 

SHOCD

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2010 PP SHO with shudder. It finally threw a P0741 code too the other day. TC clutch solenoid problems and a failure to lock on a highway speed test. I cleared the code and it didn't come back but still shudders. Takes a lot of fixed gear acceleration tests to get the code to show and is the only time I've seen the code. Changed tranny fluid and added a tube of anti shudder. Didn't go away. Third gear pulls from 15mph to 50mph, you can really feel it. BTW, Endurance Autorepair insurance sucks a big one. They denied the claim saying that 128,000 mile TC failure is "normal wear and tear". Well, all failures are due to normal wear and tear, eh? I cancelled the contract and am getting most of my money back. Just glad I figured out their claim denial game early in the contract from this test. Will use my prorated refund to get the tranny shop to change the TC to an new upgraded TC and flush the tranny out of the 6F50. Live and learn. Normal wear and tear.... sheesh.
Sorry to bring back up a dead post but did you ever fix this
 

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