4T65-E Transmission Clunk, B Platform Lucerne (impala)

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Matthew Jeschke

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I have the 3800cc w/ 4T65-E transmission. It's a 2006 Buick Lucerne (same as impala). This issue has been going on for some time. I always attributed it to a goofy Transmission control algorithm but think it might be more now.

The transmission develops a very harsh shift after driving at slow speeds. Most always can be remedied by stopping car shutting off (letting car get to sleep mode). Then restarting and driving away. Shifts smooth as silk then.

Car has 157,000 miles on it, original owner, transmission serviced like clockwork most recently at 150,000 miles. Fluid looked perfect. Although the clunk issue seems to be a bit more persistent now. Videos below:

Link to Clunk Video:
https://drive.google.com/file/d/1xEFLS2Dzjvtd4d7adQDXiAPDw2POtwrN/view?usp=sharing

Link to restart video (issue gone):
https://drive.google.com/file/d/18NbzNGaGmflW_LCR9JMy7ScDZNlsxZfx/view?usp=sharing

I have a theory as to what this is, but want to get your opinion before I tear things apart. Thanks!
 
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Matthew Jeschke

Matthew Jeschke

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The bang is from too much pressure. The question then is, why? Do you have access to a Tech2 Matthew? It would be nice to see what the computer is seeing. Any transmission trouble codes?

http://www.tripleedgeperformance.com/4T65E-Common-Problems.html

I need to get a better scan tool. I'll have to see if I can get access to one of those... but I learned this is a common issue to 4T65E transmission. It's tuned horribly... shifts are too soft which wears clutches faster and puts transmission into limp mode, which is what I had suspected. It's also possible a stuck main line pressure solenoid. I see many people change that and the accumlator springs. Sorry if I snd ignorant I don't know the exact terminology as I don't work on transmission much more than basic service.

I'm going to have to find a tech 2 or scanner that reads more of the computers.
 
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Matthew Jeschke

Matthew Jeschke

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Wow just looked at your link... SUPER helpful. I always suspected this transmission was a POS lol Especially the Buick tuning with super soft shifts. Not 100% sure but think it adapts to current driving conditions... then shifts accordingly. However, my guess is sometimes it adapts such that it puts transmission in limp mode (the hard shifts). I don't know why it simply wouldn't just shift the same all the time, a nice confident shift, not some spongy crappy old lady shift lol
 

swathdiver

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Mine is tuned (6L80) and went soft after the Y-pipe and cats were replaced. Going to have BlackBear send an update once the datalog gets done.
 

UrbanSuburban

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Sorry I'm a little late on this, my brother has the same vehicle and year, only about 90k miles though, the clutch packs are designed for the slippage in order to get the 'smooth' shifts. It also does adapt. As Swath as mentioned , a tech2 or similar scan tool will enable you to get to the bottom of the problem, look for the time in ms that the trans shifts gears, the longer it takes the higher the pressure is needed until no more pressure can be applied. I have rebuilt four of these, and includes the Regal. The 4T60 series was always a great transmission until it fails, which is to say without much warning. Your tranny may be at that stage already, you already have the miles for it. One hint though, if you do have tranny codes, the check engine light should be on as limp home mode will light it and it does effect the emissions. No lights then probably a mechanical issue within. Good luck
 
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Matthew Jeschke

Matthew Jeschke

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Sorry I'm a little late on this, my brother has the same vehicle and year, only about 90k miles though, the clutch packs are designed for the slippage in order to get the 'smooth' shifts. It also does adapt. As Swath as mentioned , a tech2 or similar scan tool will enable you to get to the bottom of the problem, look for the time in ms that the trans shifts gears, the longer it takes the higher the pressure is needed until no more pressure can be applied. I have rebuilt four of these, and includes the Regal. The 4T60 series was always a great transmission until it fails, which is to say without much warning. Your tranny may be at that stage already, you already have the miles for it. One hint though, if you do have tranny codes, the check engine light should be on as limp home mode will light it and it does effect the emissions. No lights then probably a mechanical issue within. Good luck

Thanks much, I'm also thinking it's time to have a few $$ in the bank for a rebuilt 4T60E :/ 1, Curious are they hard to rebuild? I'd love to try and rebuild one from scrapyard. 2, And when clutches fail, is it possible to drive home or do they simply stop moving all together? Thanks!

PS. I've rebuilt a SBC, LT1. And done above everything else imaginable on cars / trucks minus a transmission rebuild :| Would love experience.
 

UrbanSuburban

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Rebuilding your own for the experience is a great idea, its what led me to think about rebuilding my dads 96 buick regal 4t60 e, that and being told by Aamco that it would cost 3500 dollars to rebuild. A couple of thoughts tho if you are thinking that way. Make sure that you have a good jack to put the old one on, its very heavy. When you rebuild ensure a surgical cleanlness to your area, dirt and trans do not go along very well. Flush your lines or replace them if they are rusty, make sure the rebuild kit is the proper one. You can also get some parts upgraded at the same time. Replace the Torque Converter as well. A complete rebuild should not cost you more than 600 dollars, or you can go to Rock auto and get a complete build and install that. Keep the old core and rebuild it or send it back to get the credit. I know lots of people who think nothing of rebuilding a chevy 350 but will shy away from transmissions. Goodluck with it, keep posting as to what you want to do and any advice I and the rest can shoot their way to you.
 
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Matthew Jeschke

Matthew Jeschke

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Rebuilding your own for the experience is a great idea, its what led me to think about rebuilding my dads 96 buick regal 4t60 e, that and being told by Aamco that it would cost 3500 dollars to rebuild. A couple of thoughts tho if you are thinking that way. Make sure that you have a good jack to put the old one on, its very heavy. When you rebuild ensure a surgical cleanlness to your area, dirt and trans do not go along very well. Flush your lines or replace them if they are rusty, make sure the rebuild kit is the proper one. You can also get some parts upgraded at the same time. Replace the Torque Converter as well. A complete rebuild should not cost you more than 600 dollars, or you can go to Rock auto and get a complete build and install that. Keep the old core and rebuild it or send it back to get the credit. I know lots of people who think nothing of rebuilding a chevy 350 but will shy away from transmissions. Goodluck with it, keep posting as to what you want to do and any advice I and the rest can shoot their way to you.

Awesome :) Ideally I'd like to pickup a 4t65e from junk yard. I'd rebuild it as I drive the Buick (it still runs just I'm afraid clutches are towards end of life). I am with you on cleanliness. I may even make a corner with plastic curtain to keep cleaner yet. My biggest concern is though, I don't have a rebuild guide with the torque specs and all that. Do they make a 4t65e rebuild guide? I think with a book I should be fine.
 

UrbanSuburban

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good call on the wrecked model, you just have to ensure its the same. As far as building it, YouTube has great videos by trannyshops on the building of this tranny. Do a search. As far as a guide, Alldata is usually very good as the info is there and not too costly. Strangely GM does not include in the official Ship manual the trans rebuild sections. Only the diagnostics. You would need to if you want the Official GM manual, get what is known as a TURM, or Transmission Unit Repair Manual, it contains all the Trannys that GM produced. The Alldata will have that material as well. This wouild include the torque specs.
 

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