Torque Convertor Lock-up Strategy

[5xBuckman]

Can somebody explain what the normal TC lock-up strategy is? Does it get to a certain gear and then an rpm, lock-up and stay locked until the brakes or tapped or unlock if you coast?

Mine seems strange....I'm not familiar with the platform, so I don't know what is normal.

This is for a 2005 TB 2wd 4.2L

 

[Sparky]

It unlocks when you let off the gas, or if the engine load gets enough that it needs to unlock to bring revs up (sort of like needing a downshift).

Usually requires a minimum transmission temperature to lock up also, so it won't do it when cold.

 

[Mooseman]

Lockup is controlled by the PCM with a PWM (pulse width modulation) so it happens very softly, kinda like slipping a clutch, so you don't really feel it. So if you tap the brakes to unlock it and then doesn't seem to be locking again, it probably is. You just don't feel it but can see it on the tach.

 

[C-ya]

My TB (and a previous truck - GMC C1500 4.3) locks up at about 45 mph when it is in D(rive).

 

[5xBuckman]

Thanks....I guess it is operating normally.

 

[gpking]

I was actually just monitoring my TCC yesterday out of curiosity. I have PWM eliminated ("5th gear mod"), so your results may vary.
At operating temperature, it only completely locks up (0-3 rpm of slip) in 4th gear, which falls at exactly 45mph for me.
It will unlock when the brakes are tapped.
All other gears have it slipping from 50-700rpm under throttle.

 

[5xBuckman]

I've been researching this TC lock-up....and I've come to the conclusion that my TB is not working correctly. At a neutral throttle, at say 55mph, the TC will randomly lock/unlock....rpm drops 200-300, then it will lock again. It seems the the fix is the Transgo SK 4L60E. It has 170k miles on it. When I changed the filter (upsetting as a I could have easily done the fix then) the fluid was nasty, but there was just a minor amount of fines on the magnet.

 

[Sparky]

Does sound like possible TCC flutter.

When you do that kit you'll need some other parts (seals etc) that don't come with it. Here's a combo kit that I usually buy and install in my 4L60E transmissions - comes with everything you need except the fluid and filter.

http://www.ebay.com/itm/4L60E-4L65E...ash=item3f1166b953:g:WDkAAOSwpDdVeOGx&vxp=mtr

 

[5xBuckman]

Does sound like possible TCC flutter.

When you do that kit you'll need some other parts (seals etc) that don't come with it. Here's a combo kit that I usually buy and install in my 4L60E transmissions - comes with everything you need except the fluid and filter.

http://www.ebay.com/itm/4L60E-4L65E...ash=item3f1166b953:g:WDkAAOSwpDdVeOGx&vxp=mtr

Sparky,

I ordered a version of that kit (minus the Corvette servo). Have you installed on of these? What should I be on the lookout for?

Thanks..Dan

 

[Sparky]

I've installed 3 of them.

Just follow the directions carefully. You will not use all the parts that comes with the Transgo kit as it comes with varying springs and pieces depending on what your particular 4L60E has in it. Pay attention to the bolt lengths when putting it back together as mentioned in the directions.

 

[5xBuckman]

I've installed 3 of them.

Just follow the directions carefully. You will not use all the parts that comes with the Transgo kit as it comes with varying springs and pieces depending on what your particular 4L60E has in it. Pay attention to the bolt lengths when putting it back together as mentioned in the directions.

There is one bag that has a larger diameter white spring in it, and some other parts, that has a hand written note on it. Something like "Use these if skipping the shift kit install?

Any insight on that?

 

[Sparky]

Was that in the Transgo box, or with the other misc items?

 

[5xBuckman]

Was that in the Transgo box, or with the other misc items?

With the misc items. I'm at work, the parts are at home, otherwise I'd take a picture of it.

 

[Reprise]

Picture might be good. FWIW, mine didn't have any 'extra' instructions (handwritten or otherwise); I installed mine about a year ago, and probably had it stashed for 6mos or so before I put it in, to give you a time reference.

Personally, knowing what I know now about the stock 4L60s - I'd put this kit in whether I had an issue or not - Sparky does this - and he's never had a problem with any of them, post-install. If I ever buy another vehicle with a 4L60 (like an older 1/2 ton Silverado / Sierra) - I will do the same, for sure. Not terribly difficult, once you have one under your belt - I could probably do it in about 3/4 of a day now, taking my time and not being interrupted, and not breaking any pan bolts during disassembly

 

[5xBuckman]

So, I could use a bit of help on this shift kit install. I thought I was removing the boost valve...but, it was the TCC valve. I pulled out the retaining ring, then a washer with a hole, the an aluminum valve with a hole for a spring (which came out with the spool), but as I was ducking fluid another short steel piece dropped out. Now I'm at a loss as to the order it goes back together.

Ok, the Xtra part wasn'the from the tcc. There is a bore about the separator plate the has a short stepped steel valve ..just need to know what direction it fits in.

Mod edit: Please use the edit button if you need to add more info to your last post instead of posting consecutively within 10 minutes.

 

[5xBuckman]

So, I figure it out and got it back together. The 1-2 shift is a bit more firm than I'd like but, the converter stays locked now rather than the flutter it had.

 

[Sparky]

Sorry was really busy all weekend, no pc set up at home right now, etc
Glad you got it together. Enjoy your happier transmission!