The car is acting up again what it's doing is if I'm cruising past lock up speed 45-50 or anything higher than that and I lift my foot off the gas even a little bit it feel like it downshifts back into 3rd, won't do it if I do the same thing under lock up speed, but it'll do it on the highway constantly when I slow down a bit, and when I get back inthe gas, itshifts into 4th again
help, ! what is going on?

 

Dude im having the exact same problem right know, and no one has chimed in yet ether. Have you tryed racing to from a dig with this problem? Mine also will automatically go into lockup right after the 3rd gear shift. Let me know if you find anything out, its killing me.

 

I have a similar issue with my yank 4k stall occasionally. Only difference it locks and unlocks repeatedly and I have to pull over, put her in park, turn the car off, open and close the door so all the gadgets and stuff turn off.

Essentially what I think I'm doing is "flashing" (the pcm? tranny? the stall?) to make the problem stop. My converter locks at 37 mph in 4th gear and 32 mph in 3rd gear. It does great 95% of the time but for some reason it will have this locking and unlocking problem the other 5%. Sometimes it wont even lock at all and I have to go through the above steps to make it lock up so I'm not wasting gas.

Are you sure you converter isn't locking/unlocking? It doesn't seem right that its shifting between 3rd and 4th. Either way though, some insight would be useful from some other members...

 

All upshift and dowshifts with the 4l60e along with lockup are PCM controlled,
In the OP case I would look at the TPS as a possible culprit but you really need a scanner to watch data to see whats going on,
As for lockup issues this is likley due to engine missfire detected, (That does not means it nessesarily missing) it does mean the PCM things it is and no this will not many times set a code, I woulod suggest raising the missfire table.
Also IMO locking at 3x mph is way low the engine would be lugging this by itself could be seen as a missfire for the PCM .
Hope this helps some.

 

UPDATE
I picked up the car from the tranny shop, the convertor pump was broken?
So they replaced that and I took it inthe highway , I got on it on the ramp and it seemed fine, but once I got past lockup speed and backed off the gas a lil,
damn!!!! It did it again, locks and unlocks !!!!!!!!!!!!!
WTF ?

 

When I put in my 4000 stall, it started throwing random misfire codes and it would shutter in and out of lockup at highway speed. I had the pcm tuned to raise the misfire detection threshold.

more info in here:I just replaced my torque converter and now it unlocks randomly

 

i'm gonna go have it looked at by a tuning guy,
it only does it in Overdrive after lockup speeds, i tried it in drive and NOTHING, it was fine.
Maybe it's my converter, it is a Fuddle after all

thanks

pat

 

raise the misfire detection threshold.also raise the lock up speed ( about 50 in 4th)
my .02' Johnny

 

I have somewhet the same thing going on, only Im stationed in Germany so I cant take it to "the tranny shop".

Mine however is below 40mph. When im leaving base the speed linit is 50k (32mph) and as soon as I let off the gas the car lunges forward and backwards. I have NO rpm change and I cant hear anything out of the norm, no change in engine or tranny noise.

I have a stock LS1 with FTRA, LID, Pacesetter LT's w/ORY-pipe, Magna flow catback and a 12blt Moser w/3:73 rear, stock tranny and stock converter.

I have replaced the U-joints this year and the rear U-joint has just the slightest movemnt in it.

The rear and LT's were put in by a sponsor in late '07 and dynoed at 321rwh.

I think the rear, gear mess, is too loose and it's "catching up" when I let off at low speeds, if that makes sense.

If it was a lock up and un lock prob wouldnt the rpm's go up and down?

 

Yes the RPM would be going from high to low. Mine is about 2600 then shortly after lockup is around 2150. Just a quick question to all you guys with this same problem as me. Does this problem also make you cars run badly? Mine throws itself into a limp mode, and runs horrible after a 5+ mile drive. Any info on that?

 

no... my car runs fine so to speak,

I feel slugish now but Im told thats because Im running a stock converter with tall gears and that if I get a higher stall i would feel the gears work for me.
I do smell like Im running rich (smell of burnt mogas while sitting at idle) but then I was told that I need a tune up and that it may have been tuned that way

 

Mine never went into complete limp mode because of this problem. Before I figured it out and got retuned, I would take the car on 100 mi trips and it got to be a real pain going in and out of lockup going 70mph. It would usually hold 3rd or 4th for about 5 mi at a time, and once in a while get a hiccup and sound like it was hesitating. The hesitation would only persist if I was on light throttle, and anything more it would go back to normal.

 

Did you get the car tuned after your converter? If its going into limp mode I bet your throwing either a p0751 or p0757 code. You need these two codes deleted to solve the limp mode issue. If you dont have a scanner you can do the led mod and see if its the pcm commanding the converter to lock and unlock, or if its a mechanical issue.

I had to send my pcm back to have the two codes deleted and the tcc duty cycle maxed. Helped my lockup, but it still slips after its locked. My issue is with the converter or input shaft o-ring.

 

Not sure if this is related at all but there is a common issue with the 4L60E and the torque converter not locking or popping in and out of lock when warmed up. I had that and it killed mpg when it happened and was a pain. Eventually I was getting some really extremely harsh 1-2 shifts, but only occasionally. But when they started, it took turning off the car and opening/closing the door to reset it so it would shift normally again (for a while anyway). Installed the transgo SK 4L60E which is basically a torque converter valve fix and boom it has been great since.

Now I'm not sure about the apparent downshifting issue, so it may be something totally different and unrelated to what I just mentioned. But I figured I'd throw that out there.

 

Ok let me clear up some stuff. My problem happens whether its warm or cold. Also I can manually lock, and unlock the converter always with my ground out switch. So i know its not the converter. The computer is locking it for whatever reason. After awial it WILL NOT lock by itself at ALL. But i can still manually lock it. The major problem here is when i race it locks by itself once it hits 3rd gear. Also whatever it is makes the car run like total ****. This happens at the same time that it will not lock by itself after driving for a few miles. But once you shut it off, and start it back up the car runs fine, but will still lockup in 3rd instantly. Hope this helps to full clarify everything.

Also the car was tuned with the converter.